· oryricbt @ south paeifi e re.gional :enryirou,rneni progtamlngn l-g96 the south farific...
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Soulh Pociflc Reglonol Envlronmenl Progromme
SPREF Reports ond Studies Sedes no.90
Environmental imPactof large-scale mining
in Papua New Guinea:
Sedimentolory and potential mobilization
of trace metals from tnine-derived material
deposited in the FIy River Floodplain
byJiirg llettler
andBernd Lehmaaa
oryricbt @South Paeifi e Re.gional :Enryirou,rneni Progtamlngn l-g96
The South Farific Regional En'rd.ronuent Pmgraeueauthotises the reprodnctisr of thie material whole or iU part,in an1'form pmvid€il apfiropoiate acknooulofuenaat ie g:i-tren.
Original Text English
Prurblshed in Sepl:ember l9g5 by:Soulh Poeifie ReglonolEh viro'nm e n,f F ro;gro rnrrn e'F",O. Eox 240Apio. Westerrn Somoo
Commerclsl PtintersApio. \{esfer, rt Son loq
F 39/e5 - 4C
Fdn:ted with finsneislossisfonc,e fr,om fheU nlled N otlons Environm gnf Progrorn m e ( lJ NIEPI
loyout by Weslery Wsrd, SP,REP,
SPREP Gataloguingtnfublieation Data
Hattler, J6ngEqviro-nmental impaet of large-seale mining inFap*a Nerv Gurnea ; gedi.urentology andp'ortchtial ulobill'aansn of tiace metals fiou.m ne.derivEd mateiial d.ep.osited itr tle Fl6,River F.'losdptain / by Jiitg Hettler and BerndI;eht'rann. - Apia, Westetn Sargoa : SP.EEP,1995.
vi, 7lp, I 29rcm - (SPflEF Reports addstrrfi€saelles,; n'g. 9O).
L$IEN: 982-O4.Org5-9
1. tsnvirsaueqtal iurpaot analysis = PapuaNe:rtr Guinga. 2. Mines,and r.rtioer.al resour'ces,Environrneotal aspe,€ts ' PaBua N,ew Guirirea.[. Lehmann. Bernd. I. South P.acific R,egionalEnv,ir,onmeut Frogranls.e. III. Title IV, Series.
$68;709549
South Pocific Regionol Environment Progromme
SPREP Reports ond Studies Series no.90
Environmental Impact ofLarge-scale Mining inPapua New Guinea:
Sedimentology and PotentialMobilization of Trace Metals fromMine-Derived Material Deposited inthe Fly River FloodPlain
by
Jdrg Hettler and
Bernd Lehmann
Te cht i sche U n iu er sitcit C lau sthal
Freie (hiuersitrit, Berlin,, G erman'y
Published in August 1995
in Apia, Westem Samoa
Preface
The Ok Tedi mine in PNG ranks amongst theworld's largest copper mines. It is a majorcontributor to the PNG economy, accounting forup to 45o/o of PNG's total annual exportrevenues. The PNG Government is a 3O%shareholder in Ok Tedi Mining Ltd. (OTML).Mining for gold commenced in 1984, and forcopper in 1986. Mining for copper is expected tocontinue for a further 10-15 years.
It was initially intended that a tailings damshould be constructed to contain the mine'swaste. However for economic reasons and giventhat the area is structurally unstable, no tailingsdam was constructed. So, since 1986, 100,000 to150,000 tonnes of waste per day have beendischarged into the Ok Tedi and Fly Riversystem.
In 1989 the PNG Government set compliancestandards covering suspended particulate load,dissolved and particulate copper levels,biological parameters like fish catch, and others.It is argued by some that the environmentalmanagement of the mine is based on monitoringfor compliance with standards that have beenestablished "to facilitate the realization ofOTML's mining schedule" rather than to protectthe environment.
Ok Tedi Mining Ltd. has an extensiveenvironmental monitoring programme. Compl-iance monitoring and interpretation areassessed routinely by the company (and theGovernment), but no detailed data are availablefor public scrutiny (if at all) for at least a yearafter data are collected. This lack of publicaccountability for environmental p e rform ance isunacceptable.
Inevitably the Ok Tedi mrne evokes differentemotions and perceptions by different groups inPNG. For example, Mr Kipling Uian. the formerDeputy General Manager of OTML and nowBHP PNG General Manager, siated rn lgg3 atthe 20th Waigani Semrnar on "Environment andDevelopment" at, the Unrversrty of PNG:
"Importantl-v, the mrne has brought positrvechanges to the quality of life of neighbourrngcommunities in the previously trnderdevelopedWesteln Province. lnve.stment in proJectinfrastructure has amounted to about li300mand many of the basrc services now establishedare available to all citizens in the area,
This is particularly tlue of the road. l)ower..health and water systems, transport andcommunication facilities. These services aremeeting the basic needs of local villagers byincreasing life expectancv and provicling accessto education, employment and businessopportunities.
Ok Tedi Mining Ltd. has taken a numbel ofiniatives to encourage as nruch participation aspossible from people rn the regron and so enstrlehuman developrnent goes hand rn hand withmineral development.
Sustainable development also requires goodenvironmental stewardship. During thedevlopment of the Ok Tedi ploject there havebeen criticisms of its environmental impacts,many of thern based on inaccurate infornration.Ok Tedi Mining Ltd. is a responsible resourcesdevelopment company which recognises that allenvironmental effects must be carefullyconsidered. It is the extent of these impacts andwhether they are reversible or not, which mustbe considered in relation to the social andeconomic benefits to the communities involvedand the nation as a whole."
Whereas at the same seminar Mr Alex Maun. aprominent landowner stated:
"With the mining operation our life has changed.The loss of our rainforest and degradation of theenvironment cannot be calculated in terms ofshort-ternr money. We are rural villagesubsistence farmers who depend on theenvlronnrent for survival.
Before the Ok Tedi Mine operation our life wasparadise, we en;oyed both the aquatic andten'estrial lesoul.ces. We used the river forfishiug, washing, dnnking and transportation.We nrade gardens near the rrver banks whichlasted3toSyears.
Now we rrver people can no longer drink fromthe river nor can swrm. bath or wash clothes inthe nver'. We lack the protein rn orlr diet that!!'as fot'rnerly provided by the aquatrc andtelrestlral resources. Overflow of the Ok TediRrver has caused the wild life near the river.banks and floodplarns to disappear. Some gameanrnrals were drowned by sudden floods.
'lrt'es iu tht' tlootlplaius at'e dving corupletelylblcrrrg thc rvild life to nrigrate to other aleas.Ncrs' galdt'us al'e llo longer tnade near the riverlla nks.
I rvoull hkc to stress that Ok Tedi Miuing ist:arrsing ll'l'eversible destntction along the FlyIlirrrl An Ok Te'di River'. Wlratever rt isrlestlovrng u'rll ner.el coure back to not'tual. e.g.
crrstrlrui.tt'v land, sago swallll)s, etc' OTML isblrnging ttttsrtslatttable tleveloptnent. We
afTcctetl rtvct'peoltle thitrk rt is ttcrusense talkingltbont srrstainallle developnrent whetr the ruess
rlonc bv the Ok Tedi lUirring rs not cleaned trp."
In 1994 Oh Tedi again hit the' headlines: "Ok'ledi has to build tailings dam ' Zetpl", so says
Post Courit'r' headline on 18 lUarch 1994. Thereport gocs 0n:
"Ok Tedi Illining Ltd (OTML) will be tokl tobuild a series of danrs to dispose of mine wastesor' "ship ottt" il it leftrses. Mr Zeipi has alwaysinsisted a tailings darn be built because, he savs.the river rlunrping has darnagirlg effects on theecosvsteltts."
(\VIr. Zeipi i.s lllliltister for Enuironrnettl orr.dCott,sert'al iotl).
"[i2b case looms on mine damage" again says
Post. Cou.rier headline. this time on 4 May 1994.
Then in ltosl Oorurie,'on (; I\Iay a leport states:
"'l'he leatlel of a Papua New Guinean clanlodged a writ in the Melbottrne Srtprenre Coult.vesterdav itgainst Attstralia's biggest company'BHP, seeking trnspecified datttages for allegedlypoisonine the Ok Tedi River aud destroyrng hispeople's sttbsistence way of' life. It also allegesthc PNL} Gover:tuent. a 30 percent shareholder'in Ok Terli Mining Ltd.. had "failed. neglectedand t'eftrsetl" to enfot'ce e nvtronrnentalaHreelnents and convenants'"
These rnattels are still being dealt wrth in bothPNG and Attstralizrn courts and havc not been
resolved. Furthermore present debate continLlesbetween Govet'ntnent ministers and leaders andMr Zeipi on the 11rpe o{'courpensirtiol"r paYnrentsfor envirotrtucrntttl dautage :llld rvhethcr a
tailings dam should and cottld he' btrrlt.
The Floodplains
The Ok Tedi mine adds about 58 million tonnesof sediment to the Ok Tedi River per year. It isestimated that 30% is deposited along the OkTedi, much of the rest reaches the Fly Delta. Anunknown amount is deposited along the FlyRiver and in the floodplains in the middle Fly.Studies on the coastal and maline ecosystems inthe Fly Delta, Papuan Gulf and Torres Straitsare being done by both Ok Tedi and Australianscientists funded by Ok Tedi. Studies on thefloodplains of the Middle Fly are being done byOk Tedi scientists. and are also the focus of thisUNEP study.
OTML. in its booklel Oh Tedi, the Erwirotunerfial.d, You' states that:
"coppel in the sedinrent in the Fly River is alsobeing transported during floods onto thefloodplain where it settles into the lakes,streams aud the flooded forest' At t'hie timethere is very little scientific information to telltrs what effect thrs copper on the floodplainmrght have on hsh life, feed and breed in thisatea".
Consequently OTML has commissioned studiesof the arnounts in and effects of copper on thefloodplain ecosystems. Unfortunately, the PNGGovernment and independent researchersgenerally lack the financial and humanresources to do independent monitoring andresearch of depth and detail. Hence most studiesare done by or commissioned by OTML-
This study by Jtirg Hettler and Bernd l,ehmannis valuable since it is done by overseas scientistsfunded by UNEP and SPREP through theuniversities of Berlin and Clausthal and thetiniversity of PNG. It is apparent from theirwork that copper is being deposited in thefloodplain at higher than expected levels-Hopefully future independent seientists can
assist in deciding if this copper contamination isliliely to have biological effects, for example, iffish populations may be affected.
The present study is a valuable contribution toout present state of knowledge of the Ok Tedi/Flv River system. In fact, more environmentalresearch has been done on this tropical riversysten) over the last l5 years than probably anyother troptcal rlver system in the world. Yettht're. rs strll uruch unceltainty!
Back in, 1989 in hls 'book The Pst of Gold,.Bichard Jae.kson made a statement whieh (inslishtly nodified forr) stiil is applicable 13years later:
tln our present state of knowledge of rhewgrLinca of natural sy€tems' it is only in theaarest of oecasions that honest snvironmentalercpetts agrec as a body and confidenlly prediat ase(Iueace sf futrrre events 4ndoutcomes. The OkTedi Brotsct is not one of those occasisns.Decisions ha,ve bepn mada ib the prqiect hopingthat environnental rieks will be worti it, thatis, hopiaC thart in the light of the fants availablethe maggitude of the enrir.onmerrtal impact wlllbe min:irhal. But tbe facts available are, still. toofen'. In the OkTedi case, the expertl, ifthey are,honest, will b€ kesping their fiagere,srpssed andenvironmental monitoring syst€fts underconsta[t scrutiny ..."
and hoprug that the ennironnental da'r,agesremain accciptable,!
Q^h€kWDr Doutd,lWowbray,'Prgfussar of E- nuirontnerfial $cienre at theUtduercity of Papua New Guinea,
and, Gouerntnetfi Ad,ui.ser tn the De-parfinentafEn airotutneitt,an d' Canservatistr;
ItlE" The opinions expressed in the Frefaee arethoee ofit€ arrthor and not necessarily thoseof the SPREP.
iv
Gontents
Surnrnary-.
1.lntroductio[....,'......'......].r.'..idri.|t...r.t
2.sa.nrplinganditnalyticalh4ethodology,'..-.-....j.'..........l.....
2.1 Sampling... .......-..-i'.--..-
2.2 Analytical Methods 3
3. The'Ehvironment of the Ok Tedifly River Re-gion --.i-!.--r- 6
3,1 Geolsgy of the Mount Fubilan Ore Deposit..'*--..-."....-....j'r....r.r'..i..i 6
8 3. Geonoorpholory and Vegetation.........'..
8.3 Hydrslory and Climate ..n.i...'..........
3,.4 Aquatic Biology....... r....-........!,..;
3.5 Populatior,l,,..*.,.....
4. Input of the Ok Tedi Mine iu-to the Ok TedilFly Biver Systcn....-.'...--...---!.r-q-....,'. 11
4.1 DescriBtion of the Mining Project .r.+.!.r!'...r.:.'.-r..'..-.;....ir..?- 11
+.2 Discharge of Tailiags and tri[aste Rock.-'..-...-. ..,'...!.*..--......r!'.r"."r 11
5. Sedimentolog,y of the Fly River and its Floodplain- i'.rji'"' 1g
6,1 Natural Sedirnentary Pfocesses i.n the Floodplain,-;..i.!.i.-'-.r..r. 1B
6.9 DeposiGion of Mine-Detived Material.. ..-.-i-ri...."r.--.!,.-'r..:r...r--.i.'..'- l5
6. Foteatial Mobilizat-ion of heavy metals and hydroc'hemiehy..'..-..,--'--...a:i;.,-....-'.." 2l
6,1 tleaw MetaLe in Sedirnents of the Ok TcdilPly Biver System."...'...'..."."""" 2L
6-9 Hyilrochemietry of tbe Ok Tedi/Fly River Syetern .--.--..i.--.--r--...;-..-...-dr-.......-- n7 . Biological Impaets......-i....p..i.,,.i..
8. eonclusioRs ---1...r....,-....! 43
9. AcknowledBeuleata
Summary
The Ok Tedi copper-gold mine, located at theeastern end of the central mountain range ofNew Guinea, discharges approximately 80,000tons of ore processing residues daily, and asimilar volume of waste rock and overburdeninto the headwaters of the Ok Tedi River.
The Mount Fubilan orebody, which is the sourceof heavy metal-rich sediments deposited alongthe Ok Tedi and on the Fly River floodplain,contains a suite of base metals, of which copperis the primary environmental concern. The OkTedi River flows into the Fly River 200 kmdownstream of the discharge point, where themining wastes carried as suspended load arediluted.
This study investigated the deposition of rnine-derived sediments in the lower part of theMiddle Fly River flood-plain, and thehydrochemistry and potential mobilization oftrace metals, particularly copper, in this alluvialplain. To this end, a total of 156 sediment coresand surface sediment samples and 117 watersamples were taken frorn the upper Ok Tedi andthe Middle and Lower Fly River floodplain.
The suspended matter content in Middle FlyRiver water today is about 5-10 times higherthan the natural background of about 60 mg/I.Near-surface sediments deposited along theriver channel contain up to 1100 mg/kg copper,with the mean value is 530 (*O - 240-820)mg/kg.
Of the floodplain water bodies, cut-off meandersreceive the largest quantities of mine-derivedsediment. Deposits of up to 70 cm in thicknessof copper-rich material (with 800-1000 mg/kgcopper) were detected in oxbow lakes, whichhave accumulated srnce the nine starteddischarging residues in 1984. Very hiehdeposition rates (around 4 cm/year) of mine-derived sediment were determined in locationsclose to the creeks and channels whrch link theFly River with the outer floodplain.
Due to the flat terrain, turbid Fly River waterintrudes regularly upstream of the floodplaintributaries (measured intrusions up to 25 km).A thin layer of 1-5 cm of copper-rich material(400-900 mg/kg Cu) was usually found on thebottom of drowned (tributary) valley lakes.Copper in sediment deposited in the pre-miningperiod gave a median value of 44 eO = 25-63)mg&g.
Riverine particulate rnatter also settles down onthe flooctplain at times of overbank flow, whichleads to extensive copper contamination in low-lying swamp sites close to the r.iver. Naturaldeposition rates in the floodplain weredetermined by C14 age dating to range between0.1-1 mm/year, wrth the exception of oxbowlakes, where natural sedimentation is muchhigher. l,eaching copper from materialdeposited on swampy, vegetated floodplain siteswas detected in sediments which were alsostrongly depleted in calcite and sulfide, whichare the components most easily mobilized ofmine-derived material.
The variable water table. oxidizing environmentand acidic conditions generated by decomposingvegetation. typical features of low-lyingfloodplain swamps, facilitate the mobilization ofcopper from the solid into the dissolved phase.Water taken from swampy floodplain locationsshowed copper values of up to 50 pg/I copper inthe filtered sample (membrane filter 0.4b pm).Average copper content in mixed waters of theinner floodplain is around 9 (+0 = 5-14) pg/l; theFly River water has around l7 (+0 = 13-19) pg/lcoppef. Copper concentrations in unpollutedfloodplain waters were measured at below 2 FCll.
Nearly all dissolved copper in the Flv Riversystem rs complexed by dissolved orgaruc carboncompounds, however, a fraction of thesecomplexes appears to be labile and reactive.Comparrson of dissolved copper levels measuredduring the present study in the Middle Fly Riverfloodplain with literature data on copper toxicityand interuational water quality guidelinesshows that chronic toxicity of the metal to theaquatic community is to be expected. Sign-ificant negative ecological effects, particularlyon the local fish population, may develop with aconsiderable trme lag, since aquatic organismsat the base of the food web are the biota mostsensitive to copper.
Vi
1. Introduction
The environmental problems of mining activitieshave been receiving increasing attentionworldwide in the last decade. The shift in thesearch for raw materials outside of the classicalproducer countries to the world's marginalregions like tropical rainforests has led to a
number of environmental and social problems.
In many cases, the extraction of naturalresources has been the first industrial activitybeing developed in peripheral regions.
Requirements of infrastructure, logistics andworkforce may completely change theenvironmental and social patterns in regionswhich have previously been nearly untouched byman.
One of the best d.ocumented examples of such a
development is the Ok Tedi gold-copper miningproject in Papua New Guinea. Before theeconomic value of the Mount Fubilan orebodywas discovered in the late 1960's, the mountainwas a sacred place to the sparse population ofthe local Wopkaimin Papua tribe, who were
inhabiting one of the world's most isolatedregions.
The environmental impact of the mrningoperation, located in a difficult physicalenvironment, has been subject of controversysince the project's early planning stages. Thefact that the Ok Tedi mine works without wasteretention facilities has been in the focus of thedebate in the last few years.
The mining company is engaged in an extensiveenvironmental monitoring program and also has
commissioned a number of studies on individualproblems which have been executed byinternational research institutions andconsultants.
The present study, funded by the UnitedNations Envirorunent Programme and theSouth Pacific Regional EnvironmentProgramme, is the first independent researchproject undertaken in the area. It investigatesone of the most important environmentalaspects of the mining project. Based ondiscussions with the Environnent Departmentof Ok Tedi Mining Ltd., it focusses on the fate ofmine-derived sedrments deposited in the FIyRiver floodplain.
The project's coordinator was Dr- BerndLehmann, Professor of Applied Geology atTechnical University Clausthal. The respons-ible research officer was Jcirg Hettler, M-Sc.(Geology), of the Department of Environmentaland Resource Geology at the Free University ofBerlin. The sedimentological part of the studywas co-ordinated by Dr. Georg Irion ofSenckenberg Research Institute atWilhelmshaven. The University of Papua NewGuinea provided comprehensive logisticalsupport during the field and laboratory work.
A draft of this report was presented by the studyteam in a series of discussions held inSeptember 1994 in Port Moresby and Tabubil,Papua New Guinea, with Ok Tedi MiningLimited, the Departments of Mining andPetroleum (DMP) and Environment andConservation (DEC) of the Papua New GuineaGovernment, and the University of Papua NewGuinea.
2. Sampling and Analytical Methodology
2.1 Sampling
Sampling locations were determined with ahandheld Global Positioning System (GPS)receiver and available topographic maps ofscales 1:100,000 and 1:250,000. Water depthand bottom relief were measured with a portableelectronic depth sounder with LCD.
2.1.1 Sediments
Thirty two (32) surface sediments from the riverbank of the Ok Tedi at Tabubil and from a fewlocations in the Middle Fly region were sampledwith a plastic spoon and collected in geochemicalsampling paper bags.
The large majority of sediment samples (124)taken along the Fly River was recovered with aSravity corer.
Because of the difficult access to swampy,vegetated floodplain sites, the large majority ofsediment cores (and water samples) were takenfrom channels, lakes and small water bodieswhich were accessible by boat or dugout canoe.
The gravity corer consists of a massivealuminium tube with a backslash (floating)valve mounted on the upper end. Fins arewelded to the aluminium body to stabilize thecorer during its free fall through the watercolumn. Coring tubes of transparent acrylicglass ("Plexiglas") of I m or 1.5 m length werefixed inside of the alumimum shaft. The corerwas brought in an upright position above thewater and then released for free fall.
To increase penetration depth in the bottomsediment, a ring-shaped lead weight of l0 kgwas fitted to the alumimium shaft. The corer ishoisted from the bottom of the sampled waterbody with a rope fixed to the backslash valve,which remains closed.
The sediment cores recovered have a diameter of36 mm and a length of between 20 and 70 cmdepending on the nature of the bottom sediment.The cores, which showed no or minimaldisturbance, where pushed out of the plexiglastubes with a rubber stopper and were packed inclean polyethylene bags. On floodplain sites, thesampling tubes were driven by hand into thesediment. After closing the open end with arubber stopper, the tube was pulled out.
The sediment cores recovered were usually inthe same range of lengths as the cores fromwater bodies.
2.1.2 Water
A total of ll7 water samples in the Ok Tedi/FlyRiver system was taken. Water temperarure,pH, conductivity and oxygen content weremeasured in the field using portable electronicequipment. The reduced species NHI*, HS- andNO2- were also determined in the field using"Merck Aquaquant" reagent kits for rapid wateranalysis, based on a colorimetric method.
All water samples were gulp samples taken byhand 20-50 cm below the water surface, thevolumes ranging between 250 and 1500 ml. Thewide-mouth polyethylene bottles were soaked indilute nitric acid for two days and washed withdemineralized/distilled water before use in thefield. The containers were rinsed twice withwater from the sampling site before the samplewas taken. Upon return to the field laboratorywithrn a few hours after collection, alkalinitywas determined by titration with 0.02 mol HCIto pH 4.5 (APHA Standard Method No. 408).
The water was filtered through 0.4b pmcellulose nitrate membrane filters (Sartorius,Germany) with a portable "ANTLIA" pressurefiltration system (Schleicher and Schuell,Germany) which consists of a pneumatic pump,a 50 mI syringe cylinder and a filter holder of 50mm diameter. Sometimes a pre-filter (Schleicherand Schuell BIue Ribbon ashless) had to be usedfor highly turbid water. After sufficient rinsingof the pump and filtration system, a 120-mlwater sample was taken and was immediatelyacidified with 3-4 ml of concentrated nitric acid(Merck Suprapur) per litre of sample.
Filters were retained for gravimetricdetermination of suspended solids. Thesuspended matter content in some samples wasmeasured using a 1.S-litre "Imhoff' funnel-shaped sedimentation cylinder. Few watersamples were split and a subsample wasacidified unfiltered to determine the trace metalcontent associated with the particulate matter.Water samples selected for anion analysis werefiltered but not acidified, DOC samples werestabilized with 2 mlAitre of 50% H,SO4.
Great care was taken to avoid cross-
contamination of collected material. AtIequipment was acid-washed and rinsed withdistilled and deionised water between use fordifferent samples in the field laboratory. Blankswere included and subrnitted to the sameprocedule as the sarnples.
2.2 Analytical Methods
2.2.1 Sediments
Sediment cores were cut in halves in thelaboratory with a stainless stell knife to allowvisual inspection and taking of photographs.
Sub-sections of sediment cores were wet sieved
with distilled water through nylon sieves of 20,
60, 100 and 200 pm mesh size. The resultingsize fractions <20 pm, 20'6O prn, 60-100 pm'
100-200 um and >200 pm were washed from thesieves into plastic containers and dried toconstant weight at 80o in a drying oven' Grainsize distribution was determined after weighing.
The fraction less than 20 pm in samples selected
for clay rnineral analysrs was submitted to
gravity separation in "Atterberg" sedimentationcylinders. Of the resulting three fractions (<2
pm, 2-6.3 prn, 6.3-20 prn), the finest was used toprepare smeat" slides which were submitted toX-ray diffraction analYsis.
Samples selected for chemical analysis (grainsize <20 pm was the standard fraction used)
were shipped to commercial laboratories (ACME
and XRAL. Canada), where the sediment was
homogenized and pulverized in an agate mill.ln the "total digestion" procedure, 250 mg ofsample is digested with 10 ml HCI0a-HNO"-HCI-HF at 200"C to fumrng and diluted to 10 mlwith dihrted aqua regra.
The vigorotrs digestion procedure leads topotential loss of As, Sb and Cr due tovolatilization during HClO,r fuming' The leach,
however, is partial for magnetite, clu'omite,barrte. oxides of Al. Zr and Mn. 35 elementswere determined by inductively cotrpled plasmaspectrometry (ICP-S), of which 24 are reportedin the present study. Arsenic and antimonywere additionally rletermined by hydridegeneration with aqua regia digestion and ICP'Sanalysis.
Gold together with some other elements were
analyzed in selected satnples by neutronactivatron analysts (NAA) in a commercral
laboratory (Bondar'Clegg, Canada).
Insoluble carbon and sulfur were determined byLeco furnace, in which CO2 and SO2 gaees are
released during combustion and then detected.A l5o/o HCI leach prior to combustion wasperformed to remove soluble eulfate andcarbonates. This procedure ensures that onlyorganic carbon and sulftrr bound as metalsulfide is detected.
Two reference sediment samples, NBS 2704
Buffalo River Sediment and EEC/BCR RM 280
Lake Sedim.ent, were submitted to thecommercial laboratory for quality control-Results are shown in Table 1.
Radiocarbon age dating was performed on fivesamples of peaty sediment from drowned valleylakes at the C-14 laboratory of Kiel University,Germany.
2.2.2 Y,later
Water samples were analyzed at a commerciallaboratory (XRAL, Canada), at the laboratory ofthe Department of Environmental and Resource
Geology at Freie Universitit Berlin (FUB), and
at the laboratory of the EnvironmentDepartment of Ok Tedi Mining Limited atTabubil (OTML).
Commercial analysis for metals was by multi-element ICP-S, of which measurements for 13
elements are reported in this study. The . trace
metals copper, lead, zinc and cadmium, whichwere present in some samples in concentrationsclose to the detection limit of ICP-S' were
additionally determined by graphite furnaceatomic absorption spectrometry (GFAA) at FUBand OTML laboratories.
Major anions (sulfate, chloride, nitrate) were
analyzed by suppressed ion chromatogtaphy on
non-acidified samples, Dissolved organic carbon(DOC) was determined with a "Technicon" autoanalyzer.
Quality control for water analysis was more
diffictrlt when compared to sediments, as no
standard reference material was available'Calcium and bicarbonate values, which weredetermined by two different methods, gave acorrelation of 99% in the data set of allmeasured values.
Values obtained for blanks and measurementsof the same sample by different methods andlaboratones are given in Table 2. The analysesof blanks (demineralized / distilled laboratorywater) showed no or minimal contamination,with the exception of zinc. Reported values forthis metal have been corrected by subtraction ofzinc content in blank samPles-
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Table * Qaal"it11 corttrol.'far vtaterssinptres, in ppb. TIE sa,ne sample wors crnalysed,by threed.i,f fer en t lab o r a.to r i,es.
Sampler ad Lrbor.todet fin ppb)
w1n8"t0 &l Cfl Pb Gd
XBALICP€
FUB6fM
ld282<125 n 3. <.1
w1.t30:3. F' tn Zn Gu Pb cd
,XRAL lGF.$
FUB.GFAA
OTMLGF.AA
f26 1:61 I 4 td td
nd nd '10 5 <1 <.1
10? 76 I 5 <l 0.05
w31tr.1, Fp lln ZA Cu Pb cd
XRALICF€
FUBGFM
OTMTGFAA
t1l 21 28 <2 nd nd
nd nd 2U 1.5 <'l <.1
w u 19 1.3 <1 <.0f1
'wtt/|.1, Fe Itln Zn Crt P! Gd
xfiALrcPs
'FUtsr,GF,M
OT'II/IL GFAA
319 ll3 ll 53 nd nd
nd nd 20 50 <1 <.1
134 t6 t5 31 ,4 0.1
ui3t8.1. F. fn tul Cu Fb cd
XRATICP€
FUE 6FAA
QTML GFIAA
50 <5
nd hd
484
<5 14 nd rxt
<5 {6 <l <.1
1.3 16 <l 0.08
Blank(DDWtabwatal [e iln Zn GU Pb cd
XRAL]ICP.s
FUg GFAA
OTMLGFM
<10 <5 lt 4 nd nd
rrd nd 20 <l <l <.1
27 0.5 13 0.2 <1 <i04
$tatietical analysis of eed,ixqent arrd i+aterv,ahres was perforned ua-ing the U-S-EnvironrnEntal Prstection Ageney"Geostatistical Environnental l\sseesmeqt"s.oftware (dEO-EAS, USEPA t$SE).Geoehennieal iuodelling and speciationdetermrnation wase done with aR updatedversion sf the PHREEQE eoftware (Plurmer.Parkhurst & Thorsteaso r, 1980),,
3. The Environment of the Ok Tedi/Fly River Region
Geology of the Mount Fubilan OreDeposit
Table 3: Oh Tedi ore contpositiott
1.
3.1
Trace metal contamination of the Ok Tedi/FlyRiver system through mine discharges is closelyrelated to the geochemical composition of the OkTedi ore.
The orebody at Mount Fubilan consists largelyof an intruded and altered monzonite porphyrystock of Lower Pleistocene age, which hosts a
mesothermal. stockwork and disseminatedcopper-gold mineralization (Rush and Seegersf990). Intense weathering at Mt. Fubilan led tothe formation of a copper-depleted, but gold-enriched cap (gossan) overlying the primarymineralization. The deposit is similar to otherbig copper porphyry mines in the Pacific Rimregion. Pyrite and chalcopyrite are the dominantsulfide minerals in the protore below thesupergene enrichment zone. Average metalconcentrations in the orebody are O.75o/o ofcopper and 0.67 grams per ton of gold (OTML1993).
At the contact between the intrusive andadjacent sediments, calc-silicate, sulfide andmagnetite skarns have formed, which make upapproximately 10% by volume of the orebody(Jones and Maconochie 1990).
Porphyry base-metal deposits of hydrothermalorigin like Ok Tedi typically contain aparagenetic sequence of the metals copper,molybdenum, silver, gold, lead, zinc, iron,manganese, selenium, arsenic. cadmium,tungsten and others, which are not evenlydistributed within the orebody. but are locatedin distinct zones around the low-grade quartzcore of the intrusion. Very high values for lead(1000-3000 ppm) have been found in overburdensampled in October 1991.
The skarn mineral paragenesis has an elevatedand more variable content of trace metals ascompared to the coppef porphvry ore, and ismore critical fronr an environmental pornt ofview.
However, arsenic and mercury, whrch ilrefrequently associated with gold mineralisatton,show no enrichment above bacl<ground levels tnthe Ok Tedi deposrt.
Ore minerals of the oxide zone: cupriferous goethite
Cu.FeOOH, cuprite Cu20, native Cu, malachiteCu2CO3(OH)2, azurite Cu3(COj2(OH)2, copper
carbonates
Ore minerals of the sulfide zone: chalcocite Cu2S,
di genite, covellite Cu S ( supergen e f ormati on sl
chalcopyrite CuFeS2, bornite Cu5FeS4 (very minor),
pyrite/marcasite FeS2, molybdenite Mo52
(p rotore m in e ral izati onl
Sulfides of Se and Ag are accessory minerals in themain orebody (Fubilan Monzonite Porphyry)
Pb, Zn, Cd, As, Ag and Se minerals are found mainly in
skarn ores
3.2. Geomorphology and Vegetation
The minesite at Mount Fubilan. which had anelevation of 2094 m above mean sea level (MSL)before mining started, is located in the uppercatchment of the Ok Tedi (see Map l). The sitereceives rainfall of 10,000 mm per annum,which is amongst the world's highest.
Dense tropical rainforest blankets the ridge andravine topography. The area is seismicallyactive and prone to landslides. North of the OkTedi catchment stretches the massive Hinden-burg Range with maximum heights of 3325 m.The range is a highly unstable, cliff-like struct-ure btrild up of Tertiary Darai Limestone, whichis responsible for the high natural calcium andbicarbonate content in Ok Tedi water.
Tributary slreams in the area are very steepand form narrow, gorge-like valleys, withboulder-size alluvral debris. Upstream ofNingerum (60 m above MSL), the Ok Tedi is abraided nver, up to 100 m wide. At Ningertrm,70 km to the south of the mine. the Ok TediRiver leaves the mountaineous region. BetweenNingerum and l{onkonda. the river passesthrough a transrtion phase and enters the FlyPlatfor:m. a vast alluvial plateau wrth very littlerelief and meandering streams. 130 kmdownstlearn of Ningerum, the Ok Tedi flowsinto thc' [.ipper Fly River at D'Albertis Junctioni.rt 20 ur elc'vntron erbove MSL.
2.
?
4.
(
o.
trIop l' Th.c Fb Rirrer Rc.qiorr.
PORGE\x
Daru
oLervada
MINEEDI
| _':
/ _r{f.\
TOK
to
nl
rJt
onD*
Lake Murray
luniba
!f tut. runit
iqt?0"0"i \"*,ilENingerum /f/
ItKonkonda \
x",*i5ffrrJ
d
Obo
I
i
II
ii
0 25 50knL-l-l
142 "
South of the junction, the river channel is flatand meandering, flanked by thick jungle,extensive backswamps, lakes and lagoons. Thereach between D'Albertis Junction and theconfluence with the Strickland River south ofObo (Everill Junction) is called Middle FlyRiver, with a length of 410 river kilometers. Thesinuosity factor is about 2.4. The channel widthvaries between 200 and 300 m on average.
Downstream of Kai and Agu Rivers/Lakes, thefloodplain vegetation pattern is dominated bytall, dense reed (Phragrnites, Saccharutn) andsmaller grasses. Jungle is restricted to a fewisolated areas of higher elevation. Trees growonly in rarely inundated areas (with theexception of Sago palms and thin-stemmedMelaleuca) because of their susceptibiiity toprolonged flooding. The fact that trees arelargely missing in the lower part of the MiddleFly points to frequent natural flooding.
Lakes and shallow water bodies and channels ofthe floodplain often have a dense vegetation ofaquatic grasses, floating Azolla (Equisetum),Hstio (Araceae), water lillies, and thesubmerged Ceratophy Llurn.
Below Everill Junction, the lower Fly River istidally in-fluenced, reaching the delta 400 kmdownstream. Due to the increased flow rate anda lower gradient, the channel width andmeander amplitude are greater than in theMiddle Fly.
The Fly River floodplain is made up of an innerpart, the channel migration zone comprising thepresent river channel, cut-off meanders andmeander scroll complexes, and the outer partwith drowned vallev lakes and extensivebackswamps.
The floodplain widens from 4 km width nearKiunga to over' 14 km close to Obo.Discontinuous low natural levees, about 1-2 mabove mean river level, flank the existing riverchannel.
Drowned valley lakes are typically connected tothe river by a narrow, slnuous channel with alength of l-2 km, 3-10 m width and a depth of 2to 5 m, becoming more shallow towards the lake.The channel itself is being kept open by thescouring action of sediment particles in thewater. The lakes have a depth of about 1.5 to 2.5m, cut by slightly deeper channels, decreasing toless than I m towards the end awav from theriver.
Their bottom relief clearly reflects their originas tributaries to the Fly River. During the sealevel rise which ended about 5,000 years ago,the river ends of the larger floodplain creekswere filled with sediment derived from the FlyRiver. Water can flow freely in both directions,depending on the water levels in lakes and theFly River.
Due to the low relief. the edges of lakes or"lagoons" are not well defined and tend to mergewith neighbouring grasslands at high waterlevel. Higher banks. on which the villages areusually located, are remnants of eroded plateausof Pleistocene age. The water level in the lakesis highly variable. Following consecutive drymonths, lakes may dry out completely which canresult in massive fish kills.
3.3 Hydrology and Climate
The climate in the investigated area is wettropical. The minesite receives well distributedrainfall on 325 days throughout the year.Average temperatures show a nocturnal min-imum of 20'C and a mean daily maximum of27"C. Mean annual relative humidity is about85% in the Fly River lowland. Temperaturesare constant throughout the region with anannual mean of 29oC.
The Fly River has a total length of 1120 km. Itsmost important tributaries are the Ok Tedi andthe Strickland Rivers. The catchment comprisesmore than 76,000 kmz. The mean annual runoffper unit of catchment area is about 2500 mm,which is higher than for any other river systemin the world (Maunsell and Partners 1982). Asthe river catchment is relaiively small,streamflow is characterized by short-term waterlevel fluctuations with rapid changes betweenflood peaks and drought periods.
Rainfall is highest in the upper Ok Tedi regton,with recorded annual values up to 14,000 mm,7,800 mm at Tabubil, and decreasing in thelowland. At,I{iunga on the Upper Fly River, theannual mean is 4.700 mm. at Lake Bosset in theMiddle Fly area 2,670 mm, and at coastal Daru,2,100 mm. Rainfall and river flow show limitedseasonality. June to October usually are thedryest months in the Middle Fly region.
The long-term mean discharge rate of the OkTedi at the lunction with the Upper FIy River(flow 1178 m3/s at lhunga) was measured at 923m3/s. The combined flow is 2161 m3/s in theupper Middle Fly.
Thcrc exists it n'ateL exchtlnge between thef'loodplarn altd rts rviltet' bodies and the MiddleFlv River'. The net supply of seclitlent-poor' butDO(l-r'ich f'lor-'clplain rvater to ther Nliddle Fly'however'. apperlls to be small. At Obo' the long-telln mcirn dischalge is 22'14 trr:t/s. TheStricltlnnd Itivel dischalges llll0 m;lis into theFll' Riverl rtt, Evelill ,Ittnctiotr (OTI\'IL 199't).N'lurn daill' florv data for the last I'ew years alesumllarlzerd rn Trrble {.
Watet' lervel lluctttations in the Middle Fly r:rre
smallel thirn in ths ITppel FI-'- River. wherervirter' level chrtnges of up to 15 m have been
lccorded at liiungl. The discharge of the FlyRivel at its tnouth of 6.000 nrlt/s makes itcomparable tn size rvith the Niger and Zambesiin i\fricir ol tltc l)auube in Eulope'
Tubl.a .l; llleon d,oi|.y flou' dot.o collected by
)'ll\IL lor Lh.e Ok Tedi,, FLY atdSt ri"chl.a t r.d llr.r'crs o t tl,ifl'erenllocttl,iorLs itt the coI'clturcril.
Site 1988 1989 1990 1991/92 199493
The fish population in the FIy is remarkable forbhe large size of sone species (e'g. black bass
and barramundi) and the abundance of endemicspecies like catfish. The most bargetted species
by commercial fisheries is the barramundi Lotes
calcarifer, which roams the entire length of theFly and resides in floodplain water bodiesduring most of its lifecycle. The barramundimiglates annually to the coastal areas forspawning (Eagle 1993).
Fish ecology is characterized by an overlap ofspecies types resident in the two main habitats,the river channel and the floodplain with itswaterbodies. Due to the high biologrcalproductivity of the Fly floodplain, the majorityof the food for the Fly River fishes originatesfrom off-river sources (Kare 1992). Overlap indiet and habitat requirements is an importantmechanism for survrval since prolonged periods
of lorv water level may result in drying out of thefloodplain and its shallow water bodies (Eagle
1993). Under these conditions, the fish takerefuge to the stream channel and oxbow lakes,which may represent the only standing water on
the floodplain.
The fish populations decline substantially,however. the recovery usually is rapid withrecolonisation of the newly flooded habitat bythe surviving stocks (Smith & Bakowa f994).The most important food items for fish are
a quatic and terrestrial invertebrates (freshwaterprawns, mayfly larvae and other insects, wormsetc.), algae, plant and organic detritus'Predatory fish like barramundi and catfieh feed
on srnaller fish like Netnatalosa herrings.
3.5 Population
In the entire Ok 'ledi/Fly River drainage areaIived about ?3,500 people, according to the 1980
nattrnal census. They speak 28 differentlanguages and ftlrm five different languagelanrilies: the Ok and Awin people of the Ok Tediancl Lrpper Fly River. the Marind of the MiddleFlv and Lower Strickland (Lake Murray) region,the Strki-Gogodala people of the l,ower Fly. andthc Tre.rns-Fly peoples of the southern coastalplarn.
The rnountain people are hunter-hortr'-culturalists living a subsistence lifestyle. Fish isir mote tmportant part of the diet for the lowlandnverine people.
Flow rate (m3/s)
Bukrumdaing i
Tabubil 175
Ningerum 305
Konkonda 965
Kiunga 1435
Kuambit 2400
Obo 2515
Strickland 3785
Ogwa 6300
222 183
850 1122
1197 1044
2124 2094
2613 2424
3869 3769
5792 5461
193
456
807
1407 2061
2A57 1978
2870 3141
25 27
110 i24 27
290
805
941
' no data avatlable
3.4 Aquatic BiologY
A st.rrdy couducted prior to OTML's opelation(Robelts I978) carne to the ctlnclusion that t'he
Fly River systetn supports thc rnost diverse {'rsh
f'auna rn the Australasian regloll, with at least'
105 freshwater species from lJiJ ftrmilies. 'l'l're
Seprk Itiver rn Northern New (iuinea' the nverclnsest to the size of the Fly on the rsland. has arelatrvely low overall fish densrtv rvtth a total o{'
5? freshwatel specres (Allen & (irates 1990)-
In the Middle Fh-Lakc Murray regi.on,habitable leqd end ground suitable fsr foodeul-hvatiqn is s-carcg, TliE irth*bitarrte (sbs'{rt4,500 in 1980) are mainly hunter'gatherers whoeollect wild sago. cooklng-bananas and sugarcaqe, and rige t-he fieb reeorree of barranundi,black baes and eatfish (Busse 1991). The sale ofarocodile eirins is an important source of casl,r.
The largest Fopixlations in the Middle Fly arcaare at take Beeset, Lake Pangpa and LakeDavia,nobu. S-nall villages and homesteads areffiically located along lakes aud rivers,V,iitually all rravel. ing is fu dugout canoe.Dcdng extrem-eli dry periods' irr wlliah la-kesmay drrr o,ut co'mpletelJ" p;eople ab-andon theirviUages and move to the main rirr,ers wh,ichrer-tai[ the only source of water.
The rlevelopment of the Ok Tedi Mine ha*s
resulbed in massive cul'tural and eseioeconogrigchanges in the a{fected region, A f,or:uergovernment adrniser errrphasized the ",XLsycho'logical trauma that Ok Tedi developnrent wiltrbring to the simple life stlrliee of the bountainpeople" (Pinta 1584 .
The ndning comllany has established the "L,owerOk Tedi/Fly River Developrnent Truet'' whiehsffers basic village inftastructufe in the fieltl oftrsnspef,t, health, educafion and busiqeggdevelopr,re.ut. Ii supports an estimated 30,000people in 10[ villages living along the riuersyutem, who rnay be negatively affeqted by' sliodisehalg""""""""e of mine tes,idugs ,and assoqatedprobleme.
10
4. Input of the Ok Tedi Mine into the Ok Tedi/Fly RiverSystem
4.1 Description of the Mining Project
I\lining of thc r\'lotrnt li'ubilan orebody as ern openpit stzrrted irr 198'1, sixteen 5rsi1I's zrfter thediscover."- ol' thc deposit bv liennecottexplolation gcologists in 1968' 'fhe particularf'c:rtures of'the ot'e deposit were responsible lbrthe developnrcnt ol' the tnine in mainly twostages: from Nlirl' l()tt4 to late 1988. the gold-
cnriched cap was rrrirred and processed. Thisrnvolved the use' ol' sodiutu cyanide and otherprocess cheurrcals ftl' gold extractiort. Followingthis stage, the phase of extractttlg copper ore
comurenced. The golcl is now recovered in thesulfide fl otation concentrate.
Cr,rrrently, thc' pt'oduction is about 80.000 tons ofore and a similar volttnte of waste rock per day.
The latter is uraterial in which lhe metalcontent falls below the cub-olT grade of 0.2% fotcopper or 0.8 g/tons of gold. The copper cotrtentof the ore cttllenLly being mined is 0.84% on
average and overbttrden contains about 0.11%
(OTML 199;l). Asstrming a urean recovery rate of85%, the copper content of tailings is arotrnd0. I 3'.1/o -
The ore is crushed and subsequently f'ed ro aseries of ball rnills where the material is ground
to fines. A copper-rich concentrale. containrngall valtrable metals, is recovered by means of aconventional sulfide froth-flotation process. Fornaxunurn sulfide recovery and pyrite depress-ion. the pH of the flotation mixture is adjustedwith lime to 10.5- I I and organic process
chemicals ale added (England et al- 1991)'
The final conccrltrate is transported by a 160 kmslurry prpehnc' to bl"re rlver port of Iiiunga on theUpper Fly ltiver. r\t the l(runga whari thesltrlry is lilteled. dried and stored to awaitshiprrrent b1' bulk czrt'riers down the Fly River'Frorl a storrrge facility in the Fly River Delta.the coltccntrilte ls sold urrder long-termcontracts to surelters rn Japan' Gerlnany, SouthIiolea. I,-rnlancl and the Phrlipprnes-
In 1992, OTI\'{L pr"oduced 193,400 tons of copper
rn concentratcs. coutatmng also l0. l tons ofgold. about Zl-) tons clf silver, and other metzrls.
The rnrne' rs the world's fifth brggest copperproducer. Olt Tedi's nrrneable resel'vcs at theend of 1992 were estrmated at 4jJl Mt of ore'
sufTicient fol another l5 yeerrs ol' operation(Mitirtg ,Jort.t'rutl , Octotrer l. l9$3).
Following a recent restructuring of ownership,the shareholders of Ok Tedi Mining Limited arehelcl by Broken Hill Proprietary (51%), a leadingAustralian mining company, which is also theproject's operator; the Government of PapuaNew Guinea has increased its stake from 20 to30%: and 19% now held by Metall Mining, a
German-Canadian mining company (Milt'irr,g
Jourttol. May 6, 1994).
4.2 Discharge of Tailings and WasteRock
The tailings from the copper extraction in theruill, approximately 98% of the original feed tothe processing plant, is piped without furthertleatment to the Ok Mani, a tributary of the OkTedi. Waste rock is hauled to erodible dumpsadjacent to Mt. Fubilan, from where thematerial is washed into the headwaters of theOk Tedi.
The thickened, alkaline tailings slurry consists
of approximately 55% solids of which 78o/o havea grain size less than 100 pm. The material has
about l0-2Oo/o of its original copper content,varying amounts of trace metals ingluding zinc,
Iead and cadmium which occur naturally in theporphyry ore, and small quantities of organicflotation chemicals.
Waste rock and overburden is coarser, but has a
high percentage of soft material (siltstone andlimestone) which breaks down easily, containingcopper and significant quantities of other heavy,o"tul". Although some of the waste rockremains temporarily in the dumps and adjacentcreek valleys (depending on the rainfallactivity), most of it is washed down rapidly intothe Ok Tedi River.
Since the beginning of mining at Mt. Fubilan, allwaste rock and overburden (with the exceptionof a short period during the gold stage) has been
disposed off in the river system. Theconstruction of a tailings dam was halted inearly 1984 when a land slide forced theabandonment of the construction site, which was
located in a geotechnically highly unstable zone'
11
The larger part of the mine-derived nraterialentering the upper Ok Tedi has a particle size ofless than 100 pm and can be transported assuspended load throughout the entire length ofthe Ok Tedi/Fly River system, given sufficientlyhigh hydraulic transport capacity.
The massive input of mine-derived sedimentsinto the Ok Tedi exceeds the sediment transportcapacity of the river system, which has led tosevere aggradation of the river and a rise of theOk Tedi channel bed by ten meters and more inthe upper reaches. Riverbank food gardens andplantations have been flooded and the naturalecology of the river and subsistence fishing hasbeen seriously disrupted.
About 60 million tons of material are deliveredto the Ok Tedi/Fly River system per year,containing approximately 69,000 tons of copper.The daily discharge rates are 160,000 tons ofrock material with 190 tons of copper.
The presence of iron and base metal sulfides inthe waste rock and tailings indicates thepossibility of developing acid mine drainage(AMD), which arises from the oxidation ofsulfide mrnerals and subsequent sulfurrc acrdproduction. AMD generatron rn the Ok Tediwaste rock dumps was considered a potentiallyserious problem in the Ok Tedi EnvironmentalStudy by Maunsell and Partners (1982). LowpH in waste rock drainage may result inenhanced solubility of trace metals like lead,silver, zinc, cadmium and copper (Ferguson andErickson, 1988).
However, acid formation may be buffered byalkalinity released from carbonate minerals inthe mme waste, such as calcite (CaCO$. Giventhe relatively high calcium content in the wastematerial, development of AMD in the waste rockdunrps appears unlikely. Despite the fact thatsulfide oxidation is occurring in the minedischarges. no pH values below 7 have beenrecorded in water of the upper Ok Tedi, neitherby OTML nor in measurements during thepresent study.
12
5. Sedimentology of the Fly River and its Floodplain
5.1 Natural Sedimentary Processes inthe Floodplain
The Fly River has a highly vztt'iable flow reginewhere extensive flooding and overbankdeposition on its wide floodplain alternates withextremely low water levels in drought periods.
The sedimentary processes in the Fly Riverfloodplain are dominated by the river itself andthe suspended load it carries. Sediment deliveryby floodplain creeks and chaunels to the systernis negligable. The catchment in the outerfloodplain and the adjacent piedmont plaincomprises forested areas with some swarupsavannah. The content of particulate matter infloodplain creek waters gencrally is very low(below 15 rng/l), consisting of organic material,mainly plant debris, and strongly weathered -soil
material.
At mean flow in the Fly River and low rvatertable in the floodplain, intt'usion of t'ivet'iuesuspended sediment occurs along pre-existingchannels linking the liver with the floodplain'Sedimentation is highest in oxborv lakes aud tiechannels, whele medium to coarse silt from theriver suspended lozrd settles dorvn. and mnchlower in drowtred vztllel' laltes and floodplaindepressrons where clay ilnd fine silt tlray become
deposited.
Drainage direction throughotrt most of the FlyRiver floodplain i.s towards the Fly, although'theinner floodplain, the erctive rrleauder belt' tendsto be highcr in elevation Lhan the ottterfloodplain due to sedimentation along and in themain river channel. No broad continttotts levee
is developed along the river and where there rs a
dam. it rs cttt b1' smzrll drainage channels,
During penods cll' hrgh watel level rn the FlyRiver, whrch are assocrated wrth highersediment loads because of tncreased transpot'tenergy, rn'er bank overllow and innndatron ofthe alluvral plarn occuls. Overbank floodrngduring rnoderate floods is locahzecl close to theFly River channel rn flirnhing srvaml:s. 'l'he
water returns to ther rivcr rvhctr the floodrecedes. nlthough urost of the snspcrncled loadcarried into t.he floodplain lvill be deposrtedthere due to vegetative lilterurg in the gt'asslandbordering the uratn river, ilud iu seclttucnt flitpssuch as lakes.
Maunsell and Partners (1982) recorded a perrodof very high flow in the Fly River in JuIy 1981,
which was the highest since 1977. The waterlevel was about I m above the natural levees.According to their observation, grassland andforests adjacent to the river channel in the reachbetween Lake Bosset and Obo were flooded to awidth of about 16 km on either side of thechannel. Although this situation is highlyanomalous, it is evident from aerial photographsthat at high water level in the Fly River, turbidflood water may flow several kilometers acrossthe floodplain.
The background deposition rate (i.e. before themine started discharging material) in drownedvalley lakes is very low. Sediment fractions less
than 2 lrm were analysed from small islands (0-1
m above mean lake level) in Lake Bosset andBai Lagoon as seen in Map 2. These indicated a
mineral composition dominated by kaolinite,alurninium chlorite, quartz and gibbsite. Allfour minerals are typical of highly weatheredtropical sediments. Sediments probably fromthe Pleistocene age were found on the surface ofthese shallow islands, showing that no Fly Rivermaterial has been deposited there in the last120,000 years, when the sea level began to dropand Pleistocene sedimentation in the alluvialplain ended.
Table 5 shows the results of Cla age datingwhich was performed to determinesedimentation rates in drowned valley lakes.The overall deposition rate seems to be wellbelow I rnn/year and may be as low as 0.1
mm/year. The sediment deposition at a
particular site within a lake depends largely on
bottom reliefand shape ofthe lake.
Sarnple Core 3/30.3. was taken from the distalend of Lake Daviambu. The upper 13 cm consrstentirely of peat-like organc debris.Accumulation of this material, derived froru thecatchrnent of the lake rtself, is much slowel thanat those sites which receive suspended sedimentflom the Fly River.
With the other three cores, the sediment layerebove the peat was made up of Fly River'
matertal, as detet'mined from its characteristiccltrl ruineral assemblage with dominantly (low
charged) smectite. A thin layer of copper-richmlrteual on the top of the cores was observecl'
13
Map 2: Tlte lower port of llrc Middle FIy Riter (stu,dl oreo).
lake Hurray
Lake Aguo -4,
Kemea Lagoon
f..t',4r.'. ,',t dkc K ibuz
*tr{
n\u\,o
\\ Bosset
14
Toble 5: Resllrs of racliocarbotr age dating of sedinterfi cares front' drown'ed ualley lo,hes-
Core Number 3111.1. 115.4. 1'9.4.3'30.3.
Locality Units L.DaviambuW L. EossetNW BaiL.C KaiL.SW
Depth of peaty layer
below sediment surface
C14 age
Sedimentation rate
Water depth at site
Distance from Fly
cm
years before present
ye?rs
mm/1000 years
mean water level
air km
28272613
5265 2950 4030 4380
t215 t70 t110 *125
249567M1.10 2.40 1.70 2.60
6539
Due to the lack of dateable organic matter insediment cores frorn tie channels and theirbanks, where sedimentation certainly was muchhigher, no data are available to establishdeposition rates at these sites. The simple factthat the shallow lakes still exist after about5,000 years of possible sedimentation from theFIy River points to very low deposition rates.Assuming that the maximum channel depth of5.4 meters, measured in Lake Bosset channelclose to the Fly River, reflects the originalchannel depth of the drowned tributary, thenthe deposition rate was about I mm/year in thelast 5,000 years at sites close to the Fly.
At times when discharge from the StricklandRiver is greater than the flow of the Fly' a
backwater effect develops, which results indecreasing river velocity in the Mrddle Fly nndsubsequent settling of suspended material onthe river bed. The sarne occurs during low-tlowperiods. The deposited material rnay be
resuspended at hish flows.
Pickup et al. (19?9) estimated the naturalsuspended load of the Middle Fly at 7-10 niilbontons and bed lorrd at l-2 rnillion tons per 1'car'.
5.2 Deposition of Mine-DerivedMaterial
The strspended sediment conccnlraLtons rn tl'reMiddle Fly Rrver today are 5 - 10 tttttes above
the natural load of about 60 rng/I. Srgnificantquantitities of' mine-derived sedimcnts al'e
cleposrted and trapped in creeks, [3lis-s rind
swarnps adjacent to the Fly Rivet. Strch off-rrver sites play an rnportant role tt't thc tbod
rveh and tn the leproduction cycle of' rrclr'ratic
orgilnistns lilie rnvertebrates and fish.
Flow inversion in channele linking thefloodplain with the Fly River is an inportantprocess because it is responeible for suspendedsediment transport to off-river sites duringmean flow conditions. Reverse flow upetreamthe tributary channels was frequently obeerved
durrng the three field trips undertaken'
On April 8, 1993 slightly turbid water (sample
W1/8.4.) rvith elevated calcium, copper (9 FSil)and cadmium (0.12 pgll) levels was encounteredin the Agu River/Lake system about 25 kmupstream of the junction with the Fly River,which had about mean flow. The Agu River/Lake in this reach runs roughly parallel to theFly. As a result of a recent Fly River intrusionupstream the Agu River, turbid water was
visible in the densely vegetated parts of AguLake. whereas in the Agu main channel, Flyrvater was slowly pushed out in southerlydirection (downstream) due to heavy rainfall inthe days before the site was visited.
A sirnilar observation was made in the KaiItiver/Lake -system rvhich was sampled on April9. 1993. nlthough in this case Fly River waterwas still flowing ttpstreatn. The upstreamcllrl'el1t observed close to the Iiai River mouthw'as rt,uralkablv strong and tnade the use of theoutborrrd notol: nccessilry for passage-
Water wrth hrgh condrtctrvtty, neutral pH andelcvirtcd copper valttes (39 pg/l in unfilteredsaruplc W4/9.,1.) was encountered 19 channel krnupstr(,an1 of the Iiai ltiver confluence with theFl-\, Il.rver'. lVater ntovenlent at the samplingIocutrtrn was in northcrl,y direction (upstream)-( )ne c<luld expect thrrt there exists a flow-through tnechanrstn. tn whtch Fly River wateror"rtcts thc lirri River'/Lake system (which isabout parilllcl to thc Fly) through an upstreamcoutlL'ctl0n.
15
However, satellite images and aer-ialphotographs show no such connecting channeland give no indication of flow across thefloodplain, away from the river. The sameobservation was made for the Agu River system,although maps show a northerly channelconnection of the Agu with the Fly River.According to local villagers, this flow-throughmechanism is only active at very high waterlevel in the Fly.
The frequent intrusions of highly turbid FlyRiver water should result in widespreadsedimentation of mine-derived material in theKai and Agu Lakes. Sediment sample analysisrevealed moderate copper pollution. Only theuppermost 3-5 cm of sediment cores showedstrongly elevated trace metal contents, with Cuaround 300-600 ppm. In the Kai River samples,the contaminated sections consisted of depositedriverine suspended matter- In the Agu Riversystem, the uppermost, copper-rich sedimentswere mainly made up of humic material inwhich the high copper content may besecondary, due to adsorption on flocs of organicmatter.
Deposition of rnine-derived sediments generallyis highest at locations close to the channelswhich connect floodplain water bodies with theFly River. Comparatively coarse material(medium to coarse silt) is deposited there,whereas the remaining fractions of clay and linesilt of the riverine suspended load is carried intothe floodplain water courses shown in Figure 1
Trace metals are generally enriched in the finestparticle fractions.
In a sediment core from the Kai River channelbank (U10.4.), tahen approximately B kmupstream of the Fly River confluence, the upper38 cm showed strongly elevated copper values(400-700 ppm). This matenal must have beendeposited within the last ten years, since the OkTedi mine is operating. The sedimentation raters about 4 cm/year.
Similar observations were made at lhe otherdrowned valley lakes investigated (Bosset,Kongun, Kemea, Bar, Daviambu). Where thewell defined channels extend into the lake.substantial deposition of 2O-40 cm of copper-contaminated sediment was detected severalkilometers away from the Fly River, whereas rnthe proper lake copper-rich sedrmentation didnot exceed 5 cm.
Sedirnent core 4/11.4. showed elevated tracentetal levels in the upper 23 cm with about 200ppm copper at the bottom and 800 ppm at thetop section This core was taken in Lake Bossetat the location where channel and Iake watermc-rge. about 2 krn rnside the lake (see Map 2).
Sediruentation of mrne-derived material washighest in oxbow lakes with up to Z0 cmmeasured at sites close to the river end of LakePangua rrnd Lake Ilibuz. Twenty-nine oxbowlakes at different infilling stages exist along theMiddle Fly River.
Two sediment cores were taken from the FlyRiver channel bed (see Figure 2a-c), one at LakePangua (water depth 10.5 m) and the otherdownslream of Obo (depth l4.b m), both in thedeepest part in the channel cross section. Theentire bed core from the Lake Pangua site (b6cm) consisted of fine gr.ained sediment with bb-?5% finer than 20 pm (clay, fine and mediumsilt fraction), and displayed a constantly highcopper content of about 850 ppm.
The upper 30-35 cm of the core taken close toObo were very similar in composition, howeverthe bottom section (4I.48 cm) showed muchcoarser material with 7b% fine sand (69-200Fm). The copper content dropped to 48 ppm inthis section. From both cores, it is evident thatsuspended load has settled down on the channelfloor.
Only the section with mainly fine sand, from thesample taken downstream of Obo, shows thetypical grain size of bed load. It is known fromearlier sedimentological studies (Pickup et al.1979) that fine material does temporarilydeposit on the river bed upstream of EverillJunction. Due to the cohesive forces among finegrained particles, high current speeds arenecessary to erode these deposits. Theresuspension of mine-derived clay- and silt-sizematerial from the channel floor today may belimited because much more sediment settlesdown, and will be flushed downstream at highflows only at hydraulically preferred sites likemeander bends and immediately upstream ofthe Strickland j unction.
In this connection, it is interesting to note thattwo islands within the Fly River channel, oneimmediately downstream of Lake Bosset and theother at the lunctron of Tarnu Creek, have beenobserved during the field trips undertaken.Sediment samples taken showed relativelycoarse, copper-nch material (see Figure 2d). Nosuch island,s are visible rn aenal photographsfrom the lg60's and lg?0's. The formation ofrslands rn the river channel also indicatesinsufficrerrt transport capacity of the Fly Riverto carrJ- all mine-imposed waste material.OTML (1993) reports an rncrease in bed level atKuambrl. immedrately downstream of the Ok'fedi/t-ly lliver confluence. of more than onemetel'above the 1984 pre-mine baseline.
16
Figtp'a I : ()ottr Jtrtrt.so,t s al sed i.rrrtrtt groi,rr. siza for f'ort.r' ('ore satn.ples t'ront uarious sites ht the
I I i d d la FIt Rircr.s.t'.src,,r.
oryI
I6- A
'E too(oc !4.e J'"H Ao€ S(!a.!
c.rK E.!t'6 Eo
-.= 5:,1U EYOt
=(!r,=
c!sv?
d.?
I6
oE+.t
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U
c
:= E OEa6- n ()--eD-aP: 3Sc o ; (/)+N 5 = a\mo -- v \/^s i m>:f gr : (I:q::.! i J-e a '= d-
-.F E ja96 FNu
.9
N9
o
ntJ
06
E6obo!otEo3oE
ooo-Lo :L-G)-€
L
e9 SY= 'dovod';: dH€o€ ntor E9NOd'6 E
-D-=.t(U ,g,o-b' !olFE
orgv'5!6E.E
ondoal
cirA
5q
;
AIN\5iV t*
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^; € Ee6 c - )(C\lR€ E ory" I = --O^ i: .9 rnNN o, 5 :'>ct N I L-:@'rn € (D$
E E .>cciIS E cE@NE:f
u v,E-4': '\.c
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i( 'nHRilr c')
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ooooooooF-@!no/o
ra (I) rf) rf co (\t
or'o
l\(Onl'c')C!
o/tO
,4
ooooorf(rrN
17
Figure 2: Comparisotts of sedinent grailt size for fotr corut soltples frorn uari.ous sr,les ht the
Middle Fly Riuer systetn.
g
i*.=+EOd
aEtr
(o__'= taY so.o GN:'i cHo(Yar=
r..! ?eo tCEo'E .9rdFi =N
flGo
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t;-[J
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6 r-(\lE 9=.= >-I ;+Nt *tc;t).r= -\'d lI c')
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it
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18
Trvo ef'l'ects probably are responsible for thestrorrgl5' inclellsed deposition rates as compared
to earlier sedintentation: filstly, because of theincrease in the (mine-derived) suspendedsedirnent load of the Flv River. which today also
contains rnore silt than the natural particulateload. Secondlv, wrth redr'tced channel capacitydue to bed aggradation, overbank flow frequencyincleases. In the lower part of the Middle Fly.close to the Stricliland River junction,
aggladation of the tnain river channel is higherdne to the bacliwater effect fi'our the Stricklarld.
Sedimentaiiot't studies which were ttndertakenbefore the Oli'Iedi mine was developed (Pickup
et al. l9?9) assumed that frequent landslides,particularly in the upper Ok Tecli catchment,have lead to a high trattual suspended sedin'rent
load in the FIv River. Had this been the case'
this should have resulted in much highernatural deposrtion rates in the Middle Flyfloodplain. Tl-re courparison of sedimentrrtionrates before and after the urining at Mt. Fubilanstarted points to the fact that the backgrotrndsuspended sediment concentration in the Fly
River was very low. probably in the range of'40'60 rng/l.
Attenpts were made to establish a suspended
sediment balance using data collected by OTML'A proper balalnce would show sediment losses
(or gains) in the systeur' A brief examination ofdata in Table 6 shows that there is a largescatter in the measured concentrations over
several sampling periods.
Of main interest to the present sttrdy is the
deposition of suspended riverine material in the
Midcile Fly region. The measured suspencled
natter content in gulp samples of near-surfacewater in the FIy River reach between I(uambit
and Obo shows a strong decrease in all samplingperiods. This effect can not be seen clearly inthe depth-integrated measurements in whichthe suspended matter content is determined invertical sections through the water column.
Typically, the suspended sediment concentr'ation of near-surface rlver water (gulp samples)
is ?0-90% of the depth-integrated euspended
matter content (Higgins 1990). No such
relationship can be established in the data ofTable 6. Differences between suspended sedi-
ment content determined by gulp and depth-integrated sampling were up to 9Ao/o inmeasurements from the same site and date(data in OTML 1993).
It is difficult to explain this discrepancy, whichis particularly evident at Obo' There obviouslyexists a pronounced stratification within theflowing water body, with particulate-rich watertravelling close to the bottom. Due to the shift ofthe main current in river bends, which leads to amore turbulent (spiral) flow, the bott'om stratawith a higher suspended solids content rise tothe surface. This effect was observed in thedepth-integrated measurements at Obo where
suspended sediment concentrations are usuallyhighest close to the outer bend.
The stratification in suspended sediment
concentration within the water body points tothe settling down of suspended load on the
channel floor. River bed sedimentation is largelydependent on flow velocity, which at Obo issignificantly lower than at KuambiUNukumba'A detailed comparison of flow data gathered inFebruary and April of 1992 by OTML gave a
mean value of 1'12 m/s for Kuambit and 0'66
m/s flow velocity at Obo.
To,bl.e 6. Auerage d.o.ta otv sttspend.ed. seclJ,truent corrcen trotiorts irv gulp (surface) an'd depth'
;rlegraticl (DI) samptis. Med.ians shown and rtttrnber of nteasurem'ents in' brackets'
Dut.a fron OTML (1988-92)'
1988 9'88-8'90 10,91'9'92
ss/gulP (mg/l)
57 64
8095 10626
5846 5882
2072 nM186 149ut: utl
. 151(3) 44(5)
4709 7825(251 66e6(12)
1802 524(124) 3477(121
6e8 1420124\ 949(12). 60(24) 26(12)
305 520(24) 316(12). 171(23]t 1 18(12)
65 e2(25) 103(12)
' 414(24\ 239(12)
326 2S3(23) *
Bukrumdaing
Tabubil
NingerumKonkonda
KiungaKuambitBosset
Obo
StncklandOgwa
* nodata available
19
Ok Tedi Mining Ltd. has tried to establish anannual suspended sediment mass balance basedon its regular measurements taken in the OkTedi and the Fly River (see Table 7). Thecalculations illustrate the complexicity of thesystem and the difficulties in predictingsediment transport in the two rivers. Themeasured load values (calculated from a smallnumber of measurements) in the 1991/92 dataindicate a loss of sediment frorn Ningerum toObo (46 to 35 Mt/a), whilst the model predicts asteady increase in the same reach (43 to 5l-:
Mt/a).
In the data set for the following year, thediscrepancy between observed and predictedIoad is rninor. Given that sedirnent input by theOk Tedi mine into the system is fairly constantover the years. the massive adjustment of thepredictive model between the two years (at Obo38 instead of 55 Mt/a) is hard to understand.The flow weighted load data for 1992/93 suggestheavy erosion of material in the Middle Flybetween Iiuambit and Obo (increase ofsuspended load by 4 Mt/a), which is hard toexplain, too. This may be attributed to thelimited number of data collected (9 depth-rntegrated sarnples).
Table 7. Suspen"ded sedirnent tnass balances for 1991/92 (aboue) and 1992/93 (below) co,lutlotedby OTML (1993, t994).
Station Flow WeightedLoad (MUa)
Flow WeightedConc. (mg/l)
Predicted Load Predicted Conc.(MUa) (mg/t)
Ningerum
Konkonda
Kuambit
Obo
Strickland R.
Ogwa
46
40
37
35'
g4*
1 19'
5750
2001
646
450'
900.
323-
43
43
M
55
B5
140'
5991
1862
724
687
807
Station Flow Weighted Predicted LoadLoad (MUa) (MUa)
Ningerum
Konkonda
Nukumba/
Kumabit
Obo
40
31
34
38
35
38
38
- insufficient records: estimates based on available data
20
6. Potential Mobilization of heavy metals andhydrochemistry
6.1 Heavy Metals in Sediments of theOk Tedi/Fly River SYstem
Analytical resnlts for sediments from the FlyRiver floodplain are shown in Tables 8 and 10
(At and A3 in annex) and from the upper OkTedi in Table 9 (A2 in annex). The samples fromthe FIy River section are grouped into two
populations, i.e. sediments which were depositedbefore the Ok Tedi mine started dischargingresidues into the Ok Tedi/Fly River system(Table 8), and sedimente controlled by mine-
derived material (Table 10). This classification iseasily practicable due to the distinctgeochemical signature in the mine-derivedmaterial, which shows for some elements a
significant enrichment above the naturalbackground.
Ta.ble 8. Meatt, stand.ard deuiatiott, med.ian ualues and 25% - 75% confidence iruteruals for 27
eLetnerr.ts in Mid.d.Ie Fly Riuer backgrowtd sedimerfi sanples (rt = 128).
Element Units Mean SD Median Percentiles
7525
Na
K
Mg
Ca
AI
Fe
Mn
Zn
Cu
Pb
cd
Au
Ag
As
Cr
Mo
Co
Ni
V
Ti
Zr
La
Ba
Sr
Qn
q
ms/ks Ims/ks Img/kg I
Ims/ks Ims/ks Ims/ks Ims/kg Imsfts Imo/ko I
r.no I
Ims/Ks ]
pg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
ok
mg/kg
4365 3146
10829 4448
5335 2320
8787 7493
85538 253/,8
37302 15185
289 225
142 54
45 19
18 I0.26 0.13
6.7 6.5
0.24 0.26
4.6 3.6
61 16
1.7 1.4
13 6
33 13
165 49
3765 1269
67 25
247309 119
137 57
't7 {
6.7 9.4
1447 1445
2000 5400 |7200 14100 |3400 7200 |I4875 8025 |
71700 102400 |7200 46300 |136 334 |
115 t* |32 uol
11 23
0.2 0.2
1.0 8.5
0.1 0.3
2.0 5.0
55 70
1.0 2.0
91624 41
143 196
3100 4400
49 83
20 28
255 361
101 162
14 20
1.3 6.0
300 2525
3700
1 2050
5900
6100
91100
33700
197
130
44
18
0.2
3.0
0.2
4.0
ol
1.0
12
29
171
41 00
67
25
309
127
18
2.6
800
21
Gold gives the highest enrichment factor of 53,followed by molybdenum (factor 23), copper(factor 12), lead (factor 4.4), calcium (factor 4.1),silver (factor 3.5), sulfur (factor 2.6) andstrontium (factor 2.5).Zinc shows an enrichmentfactor of 1.6.
The elements Al>V>Co>Cr>Sc>Ni>Ti>Zr (indecreasing order) are present in mine-derivedmaterial in lower concentrations than inbackground sediments. It is evident that theelements associated with the copper-gold orefrom Mount Fubilan are also found in thelowland depositional sites. Those metals whichare typically enriched in soils during tropicalweathering are found in higher concentrationsin unpolluted lowland sedi-ments as in materialfrom the mine, deposited in the floodplain.
The comparison of mine-derived sediments fromthe Fly River floodplain (Table f0) with materialfrom the upper Ok Tedi, which consists nearlyexclusively of tailings and waste rock (Table 9),gives the following results: Calcium is found inupper Ok Tedi material 4 times and sulfur 3.8times higher as compared to lowland mine-controlled sediments.
Factors for other important elements which arefound in the Mount Fubilan orebody are: copper(2.2), silver and cadmium (both 2), zinc andstrontium (1.8), gold (1.7), arsenic andmolybdenum (1.6) and lead (1.5). The elementsK>Ba>Mg>La>V>Ti>Ni>Sc>Zr (in decreasingorder) are present in tailings and waste rock inlower concentrations than in mine-derivedsediments of the Middle FIy region.
Table 9: Mean, standard deuiation, mediant ualues and 25% - 75% confiderrce itderuals for 27elements in sedimer*s from the upper Oh Ted,i, mairtly tailings antd waste roch (n : 24).
Element Unit SDMean Median Percentiles
25 75
Na
K
Mg
Ca
AI
Fe
Mn
Zn
Cu
Pb
cd
Au
Ag
As
Cr
Mo
Co
Ni
V
Ti
Zr
La
Ba
Sr
Sc
S
mg/kg
mg/kg
mg/kg
mg/tg
mg/kg
mg/tg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
pg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mglkg
mg/kg
mg/kg
mg/kg
?/o
mg/kg
11921 4159
30350 7395
6733 1463
86117 33796
61462 11766
47512 29854
700 323
541 450
1523 976
463 744
1.6 1.3
426 381
2.4 2.5
14.9 11.5
30 12
38 14
13 10
179111 21
1788 305
22 11
zJo410 202
s76 86
7.3 2.4
1.8 0.5
15211 20643
10950
27950
6350
98450
62750
40900
775
378
1158
123
1.0
266
1.4
11
26
36
11
14
105
1750
19
22
368
548
I
1.9
7900
8100 15000
24400 37200
5700 7700
54800 1 15900
54800 65800
29300 54200
436 965
182 779
805 1791
63 488
0.6 2.2
107 609
0.8 3.3
51921 33
27 45
5 16
10 23
99 120
1500 1900
13 29
19 26
275 599
510 620
591,3 2.1
4425 10625
22
Evaluation of relationshrps between elements inthe data obtained for the upper Ok Tedisediments give the result that sulfur versus Fe,Mn, Zn, Cu, Pb, Cd, AS and Mo is stronglypositively correlated (r = 0.80-0.99, signifrcancelevel p <0.05). This can be explained by the factthat most metals are dicharged in sulfidic forminto the Ok Tedi River.
In the Fly River floodplain sediments, thepositive relationship between trace metals andsulfur is much weaker (in the range of r = 0.31-0.?l for the metals mentioned above) with theexception of iron, which shows no correlationwith sulfur in lowland mine sediments.
In sediments from the upper Ok Tedi, themetals Fe, Mn, Zn, Cu, Pb, Cd, Ag and Mo areall highly intercorrelated (r = 0.65-0.95). As in
the case of sulfur, the positive relationehip islost or becomes weaker in the Fly Riverfloodplain data for the same metals. It isinteresting to note that gold showe norelationship with any of the trace metalsmentioned above in the upper Ok Tedisediments. [n the mine-affected lowlandsediments exists a positive correlation with lead(r = 0.68) and molybdenum (r = 0.66).
There are mainly two processes operating in theriver system which are responsible for thedifferences in the element concentrations inupper Ok Tedi and lowland eediments:Sediment admixture/erosion and mobilization ofmetals from the solid phase. The Ok Tedi Riveron its 200 km long way to the FIy River junctionreceives water and suspendgfl ssdimsnts &omseveral tributaries.
Table l0:Meant, standard deuiation, medio,tL ualues and 25% - 75% con'fid'en'ce hfieruals far 27elernents in, mine-corttrolled sedinents from the Middle Fly Riuer floodploin (tr' = 197).
Element Units Mean SD Median Percentiles
2s 75
Na
K
Mg
Ca
AI
Fe
Mn
Zn
Cu
Pb
f-d
Au
Ag
AS
?t
Mo
Ni
V
Ti
Zr
LA
Ba
Sr
Sc
b
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
pg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mgftg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mgftg
mg/kgo/o
mg/kg
8010 3218
28807 11610
7242 1831
30139 23842
80994 14915
40004 11012
528 254
211 68
530 289
79 36
0.5 0.3
166 81
0.7 0.5
8.3 5.8
48 14
24 13
10521 I145 35
2753 801
44 16
267415 100
330 139
13 4
1.6 1.5
2464 2160
8200
30300
7400
24800
81 100
39500
510
204
529
80
0.5
160
0.7
7.0
46
23
10
19
139
2600
41
27'
420
3'13
12
0.9
2100
6025 9800
18850 36950
6200 8575
8200 50350
72325 91025
32200 46850
310 710
163 245
278 732
48 104
0.2
120
0.3
4.0
39
13'lI
15
123
2200
32
22
363
226
10
0.6
0.7
205
1.0
12
56
32
12
24
163
3200
52
30
466
438
15
2.0
675 3425
23
Further dilution with uncontaminated riverineparticulate matter occurs at the Ok Tedi/UpperFly River confluence. Due to the fact thatunpolluted tributaries have a much lowersuspended load than the Ok Tedi, dilutioneffects, however, are small. Lateral erosion inthe highly sinuous channel of the Middle Flyappears to be a more important process.Admixture of weathered floodplain sediment inthe river course is responsible for increasingconcentrations of elements like zirconium,scandium, titanium and chromium (which arehighly persistent in chemical weathering) in themine-derived sediments deposited downstreamin the Middle Fly floodplain.
A sediment particle which is discharged into theupper Ok Tedi travels about 7 days until itreaches Everill Junction 610 km downstream ofthe discharge point. During this time, mineraldissolution occurs. It is evident that particulate,mine-derived calcite is being dissolved in OkTedi and FIy River water. Particulate sulfideminerals, mainly pyrite and chalcopyrite, arealso unstable in the oxygenated river waters andare oxidized to sulfates. The trace metalsassociated to these minerals either go in solutionor become adsorbed to particulate matter,mainly to unsoluble iron oxyhydrates or organicmatter. They are partitioned between the solidand dissolved phase according to theirgeochemical mobility in the aquaticen'rironment of the Ok Tedi/Flv River svstem.
Table 11 shows analytical data for two sedimentcores sampled from locations close to the FlyRiver channel (Kai River channel. l/10.4.. andFly River bank at Obo, 5127.8.), whereas Table12 shows data from swampy sites (locations inTable A3).
Calcium and sulfur values are much higher thanin the cores shown in Table 12. Very little calcitedissolution and sulfide oxidation has taken placein the material from the river channel. Thedeclining copper values towards the base of thesediment core 1/10.4. reflect the developmentstages of the mine- [n the early mining phase ofgold extraction only, tailings and waste rockconsisted mainly of oxidized gossan rnaterialwith a relatively low copper content and almostno sulfide minerals, which can also be seen inthe base section of core 1i 10.4. It was frequentlyobserved that copper values increased in stepsfrom the base to the top of a sediment corewhereas gold showed the opposite behaviour(Table A3 in annex).
Sediments of Table 12 display very low calciumand sulfur values, although high lead and goldcontents indicate that it is largely mine-derivedmaterial. Gold is a very resistant element intropical weathering, and lead also shows veryIittle mobility in the Ok Tedi/Fly Riverenvironment (see following section), Copper,together with calcium and sulfur, is clearlydepleted in the sediments in Table 12. See alsoFigures 3 and 4.
Table 11. Typical uertical profiks of rnine-controlled seclirnerils (fractiott <20 pnt) ilr, the Mid.d.IeFly Riuer floodplafu depositcd o.t sites close to the riuer at higtt deposition rates.
Sediment core 1,10.4.
sec{ionCaCuPbS
ppm ppm ppm ppm
0-2 cm
24cm
'18-20 cm
28-30 cm
3&32.4 cm
32.4-34.5cm
35400 663 51 2300
44300 668 54 1700
50000 664 98 nd
56800 618 78 2700
50200 574 94 nd
35200 483 83 <100
Sediment core 5/27.3.
sectionCaCuPbAuSppm ppm ppm ppb ppm
19.5-22cm
30-32 cm
4648 cm
48700 977 76 205 5300
56000 929 79 nd 3000
47800 891 71 nd 4600
24
Ca and S remain in the sediment body when thedeposition rate is high and each layer of riverinesuspended matter is rapidly covered by freshsediment. Sulfide minerals are stable underconditions of oxygen deficiency, which aregenerated by the decay of riverine organicrnatter. The pore water in the fine-grainedsediment will soon be saturated with calciumwhich prevents further calcite dissolution.Mobilization of trace metals will be minimalunder these conditions.
Sediment corc 417.4.
section
CaCuPbAuSppm ppm ppm ppb ppm
0-2.5 cm
2.5-5 cm
7-9 cm
1 9-21.5 cm
7800 583 92 1s0 600
6600 576 122 160 300
4200 557 140 nd nd
6400 37 16 <2 <100
Sediment core1n.4.
section
CaCuPbAuSppm ppm ppm ppb ppm
7.5-10 cm
27-29 cm
33-35 cm
8700 40't 102 310 200
14000 356 79 291 500
7500 69 29 nd 200
Pop.1:f=60ppmI 1cr= 3G120 ppm
To the contrary, mine-derived materialdeposited sporadically on swampy floodplainsites is subject to intense leaching. Theundulating water table permits penetration ofatmospheric oxygen into the ss,limsnf fedy,which is faciltated by the roots of floodplainvegetation. Both factore result in sulfideoxidation. Rainwater leaches calcite from thedeposited material, and the rotting of swampvegetation generates acidic pore watere whichmay bring trace metals in solution.
Sediment corc427.3.
section
CaCuPbAuSppm ppm ppm ppb ppm
3.5-5.5 cm
5.5-8 cm
30-32.5 cm
6100 430 110 240 <100
6900 320 81 nd 100
5900 40 19 nd 100
Sediment core 1/30.3.
Ca Cu Pb ssection ppm ppm ppm ppm
2-4cm 7300 409 81 100
26-28cm 5800 35 14 400
Toble I2:Vertical profiLes of rruhrc-corttrolled seditnerfis (fraction.40 pm) deposited at swatnpysites ort th,e Middle Fly River floodplain.
Figure 3: Copper distribution of alhnio,l, seditnents itt. th,e Midd,le FIy Riuer floodpain. Theprobability graph of th,e composite population, af 385 data poirtts (opett. squares) seporatesi.rr.to approrinately log-norrnal su,bpopu,Iations (closed squares) with a, natura,l bockgroutd'of a,bou,t 50 ppttt Cu, attd, a, second popula.tiott of mhrc-d,eriued material ot 610 (geometricttttttt.tts).
l
l-.]-.1-:
-l+
J
:j
==jl+j:I-l
--..1-.l
=
99.5099.00
98.00
G- gs.ooo\
I so,oo()5 Eo.oo
e 7o.oo(l) 60.00
ri so.oo
O t10.00
.= 3o.oo(g
= 20.00
tr5 lo.oocJ
s.oo
2.00
L000.50
'''-qPop. 2:f = 510 ppm
t 1d= 42G880PPm
100
Cu (ppm)
25
tr'ittwre *Gold dictrf,butian of alluaioll, sedirnents iu, th,e Middle FIy Riuer ftoadpain. \heprobabitity graph of the composite population of 2f datu poi,nts (open squpres) seporatesinta appraxhnateX! rc-g,rtartnal euhpopalatians (clased. squares) witlt, a n:e;tural backgraundof oboat 7 ppb Au, ond, a second populntion of ninn-d,eriued, materi,at at ppb.
s(JCo=,ETE]Lo.=$EE5(J
Fly River9E.00
95.00
90.00
80.00
70.00
60.00
50.00
f0.00
30"00
Fop.2:f = 17Q ppb
t 1d= 12S250 ppb
Pop.'1,:x= Tppbt 1cr= 2.21 pgb
5.00
a00
1.m
Au (ppb)
26
6.2 Hydrochemistry of the Ok Tedi/FlyRiver System
6.2.1 General
6.2.1.1 Earth alkaline and alkaline metals
These elements have a high solubility of theirsalts in comnron. which is independent of redoxchanges and partly independent of pH (Na, It).Because of the reaction:
CaCO" + HzCO" <+ Caz+ + 2 HCO,r'
calcite dissolution re.quires the presence ofcarbon dioxide, which forms the carbonic acidconsumed in the reaction. The carbon dioxidepartial pressure in water decreases withincreasing ternperatures. Dissolved Ca, Mg andSr compounds are stable in water in theplesence of carbon dioxide.
Calcite is abundant in the mine wastedischarged into the Ok TedilFly River. Itsdissolution exerts a buffering effect on pH whichwill remain in t,he range of about 6.4 to 8.0, inspite of concoruitant dissolution of sulfides frommine discharge. Calcium forms complexes withhumic acids^ Mg compounds are, in general,more solnble than their Ca counterparts. Na isthe most mobile metal in the aquaticenvironment. I( is usually present in lowerconcentrations than Na. The natttral leaching ofI( from minerals does not result in significantlyincreased solubilization because K is usuallyreadily incorporated into new mineralstructures like clavs.
6.2.1.2 lron and manganese
Both rnetals show a similar hydrochemicalbehaviour. Manganese tends to be more mobileas compared to iron.
Compounds of I'erric iron 1Fe3*) and Mn4+,which are the stable oxidation states in aerobicwaters, are nearly tnsoluble. In reducing waters,the divalent reduced forms (ferrous/manganous)can persist in the absence of sulfide andcarbonate anions. Iron and manganese may alsooccur in both oxidation states in inorganic ororganic complexes. In oxygenated, alkalinewaters both metals are present as colloidalsuspensions of ferric resp. manganic hydroxideparticles which pass through a 0.45 Fmmembrane filter- For this reason, the "dissolved"concentrations reported for iron and manganesern neutral or alkaline waters in most cases do
not correspond to electrolyte solutions.
6.2.1.3 Trace metals
Copper, zinc, molybdenum, cadmium and leadwere analysed in waters.
Between pH 6.5 and 8.5, lead speciation in theaquatic environment is dominated by carbonatesand hydroxides (Hem and Durum, 1973), whichare almost insoluble. Pb may be complexed withorganic ligands, yielding soluble, colloidal andparticulate compounds. It can easily be adsorbedto particulate organic and inorganic matter,which is the dominant mechanism controllingthe distribution of lead in the aquaticenvironment above pH 6 Garrah and Pickeringr977).
Copper generally shows a higher geochemicalmobility than lead. The distribution of copperspecies in the aquatic environment depends onpH and on the presence ofinorganic and organicligands. Carbonates and hydroxy-anions are thefavoured inorganic complexing ligands inoxidized freshwaters with pH above ?. In thepresence of soluble organic matter, sorption ofcopper to particulates may be relativelyineffective because complexation with humicacids is the dominant process (Jackson andSkippen 1978).
Cadmium and zinc are characterized by a
lower affinity to carbonate and hydroxy anionsat near neutral pH values. The influence of pHand alkalinity on the solubility of Cd2+ and Zn2+
is much lower as compared to lead and copper.Zinc also forms complexes with humicsubstances, a process which is favoured byincreasing pH.
Molvbdenum occurs in oxidized waters as
molybdat" 6[o042-) and bimolybdate (HMoO4-)anions. The anions are readily adsorbed by ironand aluminium oxyhydroxides at pH valuesbelow 5. Above this value, molybdenum innatural waters is essentially dissolved.
Alurninium in the aquatic environment ismainly present in the form of dissolved andcolloidal aluminium hydroxide, AI(OH)e' Itsminimum solubility is at pH 5.5-6. Above pH6.5. soluble aluminium exists primarily as
al(OH)+- It is capable of forming complex ionswith inorganic and organic substances.
6.2-1.4 PH
The pH value in the Ok TediiTly River systemis not only controlled by the dissolved carbondioxide concentration in waters and calcitedissolution, but also by the biochemicalprocesses of photosynthesis and respiration.
27
Photosynthesis of subaquatic plants isaccompanied by the assimilation of ions such asNOJ-, NH4+ and HPO.2-. Charge balance ismaintained by the uptake or release of H+ orOH', which lead to alkalinity changes.
Alkalinity increases in oxygenated waters as aresult of photosynthetic nitrate assimilationaccording to the bulk reaction (Stumm andMorgan 1981):
106 COz + 16 NO3- + HpO42- + 122H20 + 18FI+
<+ Clo6H26ootroNtaPr (mean algae
composition) + 138 Oz
NH4+ is the dominant nitrogen species inreducing waters. NH*+ assimilation duringphotosynthesis causes a decrease in pH:
106 COz + 16 NHn+ + HPO42- + 108 HzO
c+ cl06H2caolroNrapr + 107 02 + 14 H+
Respiration of plant material leads to reactionsin opposite direction. When photosynthesis andrespiration are in overall equilibrium, no changein pH will be observed, although there exists apH variabfity over the day/night cycle. Whenthe rate of production of organic matter(assimilation of NH4l is larger than the rate ofdecomposition, alkalinity will decrease. peatformation, which was frequently observed in theFIy River floodplain, leads to low pH values inthe overlying water.
6.2.1.5 Reducedspecies
NH4*, HS- and NO2- were determined in watersas indicators of reducing conditions. All threecompounds are unstable rn oxygenated water.Nitrite is metastable in both reducing(conversion to N2 and N2O) and oxidizing waters(nitrate formation). The stability of NH4+ andHS- is pH-dependent. HS- is converied tovolatile H2S at pH values below ?. To thecontrary, NHa* forms volatile NHg at pH above9 (at 30'C).
Within the pH range observed in theinvestigated waters with oxygen deficiency, onlyNHa* waa a reliable indicator of reducingconditions. Many redox reactions are slow anddepend on biological mediation, hence theconcentrations of species encountered in naturalwaters may be far from those predictedthermodynamically (Stumm and Morgan f g81).
Only the elements C, N, O, S, Fe and Mn areimportant participants in redox processes in theaquatic environnent. However, since themobility of trace metals is influenced by theadsorption to Fe and Mn oxides and fixation inreduced species (e.g. formation of metalsulfides), redox conditions are of importance topredict trace metal behaviour.
6.2.1.6 Disso/ved organic carbon (DOC)
The term DOC is a sum parameter for a numberof polymeric organic substances which contain asufficient number of hydrophile functionalsroups (-COO, -NHz,R2NH, -RS-, ROH, RO-) toremain in solution despite their molecular size.Polypeptides, amino acids, certain lipids,polysaccharides, humic and fulvic acids andGelbstoffe belong to this group. Humicsubstances in general are a result of thetransformation of biogenic material. DOC levelsin interstitial waters of deposited organic debrismay be much higher than in the overlyingwater.
Humic acid is extracted from humic matter inalkaline solution. Fulvic acid is the humicfraction that remains in acidified solution and issoluble over the entire pH range. Humin is thefraction which cannot be extracted by eitheracids or bases. Structurally, the three groupsare similar; differences are in molecular weightand functional group content. The analyticaldetermination of soluble chelates in naturalwaters is very difficult, particularly with theminute quantities of metal ions that are usuallypresent.
Humic substances have a strong tendency tobecome adsorbed on inorganic surfaces likehydrous oxides and clays through a mechanisminvolving ligand exchange of humic anionicgroups with HzO and OH- of mineral surfaces(Tipping 1981). These negatively chargedcoatings may themselves become activeabsorbers of trace metals. Colloidal iron andaluminium oxides are stabilized by humates. Inhighly dispersed form, these colloids passthrough an 0.45 pm membrane fi.lter.
The most important feature of humic and fulvicacids is there tendency to form complexes withmetal ions. As polycarboxylic acids, humatesprecipitate in the presence of dissolved Ca andMg due to coagulation. Humic substancesdisplay colloid-chemical behaviour.
In the present study, three types of water weredistinguished for their different chemistry andmain constituents: Fly River water, unpollutedfloodplain waters, and mrxed waters.
28
6.2.2 Fly River Water
\\'atel fi'om thc Nliddle lrl.v Iliver (Table 13 andTablc A.t in tlre Anrrex) is charactelized by a
nrodcralelv high content of' earth alkaline and
allialine nrctlls u'hich is dtte to the activenrinelal clissoltttion ol' 1i'eshlv eroded tocknrat.erial rvhrch is caltted in sttspension from thcNtount l'-ubrlln lnrnestte and the Ok Tedicirtch ur e tr t.
'fht urirjol trniot't is lricarbonate. followed by therrrinor aniotrs sr.rl{irtc, chloride and nitrate. Thecloruinirting drssolvcd electrolytes are calcium;rnd bicarbonittu. rvhich accottnl lbr approx-imatelv 90'% of'conductivity (calculated fi'om nrol
equivnlents). itncl rvhich also control themoderat,eh' allialirte pH of 7.7. The content ofdissolved organic carbon (DOC) is fairly high ataborrt 6 mg/l (low trutnber of samples, notrepolted in Tables).
Oxygen satttration ltteastll'enrents of Fly Rrverrvater gave a tneirn valute of only 66% which isobviously inflrtenced by the oxyElen-consumitrgdcrcay of dissolved and particulate riverineorganic matter'. Reduced species (NH.r+' HS-'
NO2) were plesent at or below detection limitrvhich indicates ox-vgenated conditions.
To b Ie I i] : II eq r r,. st.ot ul.ar d de u ia t io t r,, nrc d iol tRi.vttr uto.l,er- so trtples (n' = I I ).
Within the temperature range observed in FlyRiver water, pco:l does not change to an extentwhich would markedly affect calcite dissolution.The plot of pH versus calcium (Fie. 5a) shows asignificantly negative correlation G <0.05). Theplot of suspended solids versus calcium (FiS. 5b)
displays a significantly positive relationship. Itcan be concluded that at low pH' more calcitefrom the suspended particulate fraction isdissolved, which means that the dissolvedcalcium concentration is controlled by pH(assurning constant atmospheric pcot.
The fact that the highest suspended solidconcentrations are associated with the lowestpH values may indicate that high flows in theFly River are associated with low pH. Since highflows are a result of heavy rainfall. and because
rainwater is saturated with atmospheric CO2,
the increased input of carbonic acrd may explainnear neutral pH values in the river water athigh flows.
There exists a positive relationship betweenconductivity and suspended solids (p <0-05' Fig'5c). A high concentration of suspended matter isassociated with high values for earth alkalineand alkaline metals (Ca, MS, Sr, Na and K)-
rnlues uad, 25% - 75oto con"fidence iltteruala for Fly
Parameter Unit Mean SD Median Percentiles
25 75
Temperature
pH
Conductivity
Oxygen Saturation
Suspended Solids
Na
K
wd
Mg
AI
Fe
Mn
Zn
3u
Pb
Mo
unnI rvv3cn 2-uvd
pS/cmot
TO
mg/l
ug/l
ug/l
pg/l
pg/l
pg/l
pg/l
tjg/l
PVrl
pg/l
pg/l
pg/l
ug/l
pg/l
mg/l
mg/l
28.2 1.6
7.7 02
138 15
66 0.2
199 149
1564 299
622 87
29380 6654
1237 170
172 36
below dt
72 102
18.4 13.2
9.2 6.2
below dr
196 11.8
below
7.9 5.0
77 4,0
5.0 2.5
28.9 26.4 29.4
7.7 7.7 7.8
136 128 146
64 60 68
| 1s5 92 207I
| 14zs 1350 1660
| 615 536 667
I zoooo 24750 31300
| 11eo 1075 1345
| 158 144 181
itection ttmit of 501tg/l I
lso875I rz,s 8.5 25
I uo 4.0 10.5
ttection limit of 0.1 1tg/l I
I rz o 13.0 1e.3'detection
timit of 1 1tg/t I
| 70 3.0 12.0
1767378I s.s o.o 6.0
29
Ftgure 6;Ecahur pletl for setrected: Wrarnaters ilt FIy Biner watcr (Fi,g. fia,e) on'd, floadptailt'111:6fisrs (fiA, 5d),
fr.g.5a Fie.5b
8,?
8.1
I
7;:9
7.A
T- z.t'
7.6
7.5
7..4
7.3
7.2
W6e
000
s00
400
.o,
E soo
U1an
200
600
w.5d
t&0
160
t+0
I 2t0
\ rooofI
a80e0
40
2D
100
222{.26283039Cqleium'
77 ?4 26 28, S0 52 54 5:6 5,8
Ccleium mgll
r l'
lD t5 .20 25 30 55 .40 45
eondtrctivity pS/cm
42
\o|E lso(rl'v1
200
t00
r r00,
120 110 140 150 160 170 180
Gonductivit'y pS/crn
30
No correlation was found for suspended solidsversus F-e, Ivln and Mo. A negative correlationbeLween sttspended nratter and dissolved copper
and zinc was observed, however statistically notsignificant. Na, Ca, Mg and Sr ale highlyintercorrelated.
Sample Wl/21.2.. which has the highest Fe
value of 339 ug/I, also gave the highest values
for dissolved Zn and Cu. In the acidified watersample, the colloidal iron oxide particles are
dissolved and adsorbed trace metals are
released. This explains the high Zn and Cu
vellues associated with iron- This correlationwas not obsen'ed in other samples.
Dissolved trace metal levels, with the exceptionof copper (rnedian value: 17 pg/l) are generally
low due to alkaline pH and high bicarbonatecontent. Solubility of inorganic coppet species inthe pH range neasured in the river water ts
very low. The fact that, in spite of the high
concentratiou of suspended matter (which offersadsorption sites), dissolved copper values are
relatively high. points to the plesence of soluble
organic copper cornplexes'
Analytical data from the pre-mining period(Maunsell 1982, Iiyle 1988) are of poor qualityand make cornparison with present data
difficult. Dissolved calcium concentrations are
reported to have been in the range of 13 to 16
mg/l, which corresponds to about half of thepresent values. Fly River water has a highnatural content of earth alkaline and alkalinemetals because of the limestone formationsmainly rn the Ok Tedi catchment.
Fly River water chemistry probably was notmuch different f'rom present day conditions,although Maunsell (1982) and l{vle (1988)
report slightly acrdrc pH values rn the range of5.5 to 6.7 which appear erroneous. Trace metallevels measured by Maunsell (1982) were at or
below the detection limit of 1 ptg/l with the
exception of Fe. Mn and Zn. Pickup et al. (f979)
report mean suspended solid concenbrations inthe range of 60 to 80 mg/l for the Middle Fly and
note that "the Fly and the lower Ok Tedi are
very clean rivers by Papua New Guinea
standards".
6.2.3 FloodPlain Waters
The term floodplain waters is used for courses ofwater which clrain the outer Fly Riverfloodplarn. Therr catchment comprises forested
areas and low-lying swamps of high biologicalproductivity with dense subaquatic and swamp
vegetation. The main features of floodplainwaters are low pH and conductivity (Table 14
and Table A5 in annex) and their yellow-brown
The content of suspended solids is very low as
compared to the Fly River. The materialretained on the membrane filter is orange
brown, consisting of iron oxides (about 10-15%
Fe) and particulate organic matter. The highcontent of iron. most probably in the form ofoxyhydrate colloids, is particularly evident inthe non-filtered water samples, but also in thefiltered water in which the iron values are much
higher than in the Fly River water. Sodium, an
ubiquitous element, is present in floodplainwatei-s in a similar concentration range as in theFly River. Aluminium values were highest atIow pH and conductivity (Fig. 5d)' The overall Alcontent was higher than in the FIy River, where
the metal was below the detection limit (50 ps/l)
in the four samples measured.
An influence from the mine discharges was
detectable in some water samples (slightlyelevated trace metal, calcium and sulfate levels)'
However, since the main features of floodplaindrainage such as low pH and conductivity and
high DOC levels were observed in these
samples, they were included in this category'Metal levels for Cu, Pb, Cd and Mo in floodplainwaters unaffected by mining are at or below
detection limit (e.g. tZ Pgll for Cu, Table 14)'
Zinc is the only heavy metal present inmeasurable concentrations. Since floodplainwaters drain lowland areas of intenselyweathered. Pleistocene sediments, extremely low
trace metal are to be exPected.
Low alkalinity is a result of active accumulationof organic material. Peaty sediments were
repeatedly encountered during lake bottom
"o"i.rg. Oxygen deficiency in stagnant or slowly
rnoving, warm waters does not allow complete
respiration (oxidation) of organic matter' There
rs a positrve correlatron between tenperatureand oxygen saturation (Fig' 6a), which is
contradictory at first sight- However, theoxygen measured was a result of photoeyntheticactivrty. which is highest at intense sunshine,
which in turn is responsible for high watertemperatures.
It is obvious that the waters are not in redox
equilibrium. The photosynthetic- oxygenpr:oduction masks the overall oxygen deficiency
of the system, which is evident from the
relatively hrgh concentrations of reduced species
like NHj* and HS-. Of both compounds, NH4*is the better indicator of reducing eonditions
because hydrogen sulfide is volatile at the lowpH and high water temperatures measured'-I.lHn"
tho*s a significantly positive correlationwith dissolved organic carbon (DOC) (Fie' 6b)'
which is also positively linked with water!en1perature.
colout' ("blackwatcr").
31
Fammeter Unit Mean SD Median Percentiles25 75
Temperafure
prl
OonduetiMty
Suspended .Solids
Na
K
ea
ttrlg
Sr
AI
Fe
Mn
Zn
cdCu
Pb
Mo
HC03'
NHr*
so41
DOe.
.cc
pSrcm-
mg/l
pg/J
ugfl
ugllpg/t
ugilpgn
ug/t
pgn
ugil
ugfl
ug/,1
pg,l
ug/l
rngll
mgll
mgn
mg/l
30.6 2.2
6,0 0,5
2&.5 10
v1 11
1,23X 409
188 10?
4295 1992
477 141
27 10
6V 48
13
0.3
0.37
9,4
15,1154
6:5
a.2
0.26
3"0
30.0
6.0
27
19
1 140
193
41 10
480
u64
13
0_20
0.27
8:0
29,2 31.4
5,7 6.4
2A 34
11 Z4
1020 t2€0
89 244
3060 5890
3V2 499
21 34
25 80
$: 1'l
0,14 0.38
0.18 0.45
7.0 't1.0
values highly,variable
7.5 2.5 27
;hse to detecton limitof 5 pg/l
nlourdeteofon lirnitof 0,1 pg/l
:lo.m ts de-tection lirnitoI2 pg/l
belor detection lirnit of 1 pg/l
belorr detecton llmlt of 5 pgll
Table | 4: Meq,tt, st a nd,trd, deuiatiort,fl:aodplain, wate:r sanBl,es (n =
meanl ua,hxes and, 95'"/, -
r5).V5% coufid.ertcc irtte:n:r.is for outer
Ffuure 6;Sca0lerplods for sel,ected petra,t*tzrs i,rr,l,:lnad,plah,t wsi,ets (Fi6 6o'6b),
Fig,.6a Fis.6b
I60
't 40
il20
100
80
60
40
20
0lt I
2V 28 29 50 31 32 33 34 55
Ternperoture oC0 2 0:5 0.4 0i.5
]irll-{4 mgrrl
rg
\rootE
5 r,nt-qC)t2.gc8,'tlg
O
Eg6o.96o
\o6\tro
UL
qv'1
coO)
xoa
r{
3.7
32
0.1 0,6 av
NH+* and DOC ale both a result ofdecomposition of' organic ttratter. The DOCploduced in ofT-river sites ts ihe nratn source oforganic ligands which are responsible for traceruetal courplexation rn polltrted waters.
6.2.4 Mixed Waters
Mixed waters are ge nerally intermediate incompositiou between Fly River and floodplainwaters, although the influence of the Fly Riveris clearly dominant (Table l5 and Table AG inannex).
Due to the generall.v- {iat terrarin. the locatlon ofthe mrxrng zone of {loodplarn drarnage and FIyRiver water depends marnly on rainfall in theupper catchtnent of the Fly River/Ok Tedi and inthe Fly River lowland. When there is highrainfall in both catchrnent areas, the mixingfront between Fly water rich in suspended solidsand blackwatet li'om bhe floodplain will be
located close to the mouths of creeks and tiechannels.
At high flow conditions in the Fly River andpreviously little rainfall in the lowland, riverwater intrudes several kilometers upstream ofthe channels and lakes which drain into themain river under reverse conditions' Theintrusion of FIy River s'ater is associated withtransport of mainly mine'derived suspendedmatter, which is deposited in the waters of theinner floodplain. Hence, it is not possible todistinguish between dissolved metals in mixedwaters which are directly derived from anintrusion of Fly River water and those that maybe rnobilized secondarily from the sedimentsalready deposited.
Because of the different composition of Fly Riverwaters and those draining the outer floodplain,the physical and chemical interactions occuringare of environmental interest. Particularattention has to be paid to the behaviour oftracemetals, of which copper is the most relevant.
Toble 15. Mean, stondarrl d.euiotiort, rnedion ualues and.25% - 75% con'fidertce interuals formixed u)a.ter so,,,tples (n' = 65).
Parameter Unit Mean SD Median Percentiles
7525
Temperature
pH
Conductivity
Oxygen Saturation
Suspended Solids
Na
K
Ca
Mg
Qr
AI
Fe
Mn
Zn
Cu
Pb
Mo
HCO3'
NHa'
Sooz'
DOC
pS/cm
%
mg/l
ug/l
pg/l
pg/l
pg/l
pg/l
pg/l
trg/l
trg/l
pg/l
pgil
pgil
pg/l
psl
mg/l
mg/l
mg/l
mg/l
30.1
7.1
119
77
'15
1480
385
21 900
1140
138
25
145
2.5
12
close to detection limit of 0.1 pg/l
11.3 |
close to detection limit of 1 Pg/l
28.9 31.7
6.6 7.7
80 151
41 107
7281185 1755
272 603
13425 28050
881 1345
82 176
25 101
32 457
2.5 24.5
619
30.2
130
77
36
1 587
539
21 390
1226
150
102
357
82
15.4
11.8
/.6
53
0.21
2.5
9.0
2.0
0.8
on
42
72
541
657
8372
725
111
rqo
50n
308
15.5
14
9.9
28
0.16
2.0
2.5
5.0
47
0.15
2.1
9.0
0.10
0.7
7.3
0.25
3.4
11.0
2.5 9.0
39 62
33
As mentioned above, the pH of floodplain watersis much lower than in the Fly River. Decreasingalkalinity may lead to increased heavy metalmobility due to desorption from particulatematter and formation of free dissolved metalspecies.
The plot of pH versus Ca shows a weaklypositive correlation (Fig. 7a). Mg, Sr, Na, K andHCO"- give similar plots. Calcite in particulateform carried into the floodplain waters is rapidlydissolved and exerts a buffering effect on thelocal waters. Opposite to the main trend in thepH/Ca plot, there are samples showing a highcalcium content at comparatively low pH. Thesedata are from small ponds on the swampyfloodplain and slightly acidic floodplain seepage,i.e. extremely iron-rich water trickling fromexposed channel or river banks into the riverduring low flow conditions.
No clear influence of pH on dissolved iron andmanganese concentrations was observed,although the highest Fe values tend to beassociated with low pH.
None of the trace metals showed a significantcorrelation with pH. The plots of pH versus zinc(Tig. 7b) and cadmium display a slightlynegative trend. No correlation between pH andCu (Fig. 8a) and pH and Mo was detected. DOCand pH are weakly negatively correlated (Fig.8b) which is due to the acidic nature of humic
and fulvic substances. In the absence of calciumbicarbonate buffering, the organic acids controlwater pH.
Reducing conditions, indicated by an elevatedNHo+ content, also seem to have little influenceon dissolved trace metal concentrations. Onlyzinc gave a moderately positive correlation withNHa*'
Ca shorvs a weakly positive correlation with Mo(Fig. 9a). A positive relationship of the alkalineand earth alkaline metals with sulfate (calciumversus sulfate, Fig. 9b) was observed. Elevatedconcentrations of Ca, Mg, Na, K, and Sr areclear indicators of the influence of minedischarges. High sulfate levels are a product ofactive dissolution of mine-derived sulfideminerals. Although the metals iron, zinc, copperand molybdenum are discharged into the riversystem primarily in the form of sulfides andundergo oxidation to sulfates, no positivecorrelation between sulfate and any of themetals was observed. Iron and zinc evendisplayed a weakly negative relationship withsulfate. This illustrates the complexity ofsolution chemistry in the investigated waters,and the fact that aqueous metal transport is notcontrolled by sulfate complexation. There wasalso no significant correlation of dissolvedorganic carbon (DOC) and trace metals found.OnIy the plot of zinc versus DOC shows aweakly positive correlation.
Figure 7:Scatter plots for selected, parameters in, ntixed uaters (FiS. Ta-7b).
Fig.7a Fis. 7b
- 60
o,Eso(-c.l ao
EO:O
90
80
70
60
90
80
70
1
.E ooN
20
10
9.5
20
10
0
I
IIt
I r tl t
I, tt, ir r ,l -rt
ri 'lI.
t,t t
tII
rtl
I
I
t ,r I
r r I tr r t
. I rr r-f - I
rlr, | | -- ' , ,r t artt!* I
r lra tttt att0
7.3 8
pH7 7.5
pH
85
34
55 6 b.) 8.5 ql
Figure 8: scatter pLots for selected pararneters hr, mixed waters (Fig. 8a-8b).
60Fig. 8o
rt
tlrl If
II
I{
ttttI I' I
tttl rItrl
trlII
I II
Iatr
I
Fig.8b
rI
rtl
I
rT
I
II
II
40
o)12trLc.o-ot0LU
cng)
6-no)
o
.U4o
rDl-Llno-*o.
or)-2o
l0
L05.5 6 6.5 7 7.5 I 8.5 I 9.5
pH
Intercorrelations between elements in mixedwaters are very high in the group Ca, Mg, Sr,
Na, K and HCO3-, with the exception of Na
versus K. Zn and Cd display a positive
correlation, too. A significantly positivecorrelation was found for Al and Cu inunfiltered water samples (Fig. l0). Aluminiumhydroxide may complex or adsorb dissolvedcopper. Al/Zn displayed a similar correlation. Fe
versus Cu in unfiltered water shows no cleartrend. Fe is weakly positively correlated withDOC and Mn.
The heavy metal concentrations in waters of theFly River inner floodplain, the zone of mixedwater, are of particular interest because of theprominent role which off-river waters play inthe ecology and biological productivity of theentire rrver system.
Dissolved trace metal levels in mixed waters are
controlled by a number of abiotic and bioticfactors. The most important inorganic factor isthe moderately high bicarbonate content of FIyRiver water and the high earth alkaline metalconcentrations, domrnated by calcium indissolved and particulate form, which are
responsible for the neutral to alkaline pH valuesin mrxed waters. The most prominent biotrcfactor ate the dissolved organic carbon
substances which play a very important role as
complexing agents.
Both factors interact in a complicated mannerwhich cannot be predicted from thermodynamicequilibrium calculations.
Despite the fact that lead in mine wastes isclearly enriched above background values, the
dissolved metal contents were in the great
majority of samples below detection limit (< Ipgn;. El"rr"ted concentrations were found onlyin unfiltered samples and in a few samplee
whrch also showed a high content of presumablycolloidal iron and manganese, which offeradsorption sites for lead.
Speciation modelling of inorganic lead withpUnpnQp suggests that at near neutral pHvalues and oxic conditions in waters, more than7\o/o of soluble lead exiets in the form of thePbCO3o complex which easily precipitates out'BetwJen 0-30% of lead may be present in thefree ionic form Pbz+ under the environmentalconditions in the floodPlain.
Cadrnium and zinc Erre among the geo-
chemically most mobile elements. Their mobilityis less pH dependent as compared to lead' Cd
was found in concentrations above detection
limit (> 0.1 pg/l) only in waters with a pH below?. Because of the low Cd values in miningresidues, the metal is not considered as being ofenvironmental concern. The same holds true forzinc, which showed a similar concentrationrange in all waters investigated.
5.5 d.)7.5t
pH
6.5
35
Figure 9: Scatter plots for selected paranrcters ilt rttixecl u:eters (Fig. ga-gb).
Fig. 9a ,o Fi.g. 9b ,45
10
oc4
J
q,aJoE
3zs
_o 20
o> 15
ID
n
Figure 10:
r0 20 l0 40 50 60 70 F,') 9,)
Colcium nrg/i
Scatter plot for Al uersus Cu
0
in mixed wa.ters.
D l0 l0 i0 4r) 50 60 7a
Colciunr mg/l
Molybdenum. because of its anionic form inwater, showed a different behaviour than theother trace metals. Highest concentrations wereusually found in alkaline waters, or linked withhigh calciurn values. Mo as well as Zn isconsidered an essential element to biota. Theconcentrations observed are much below thetoxrc threshold.
Copper is an essential element to plants andanimals, too.
Because of its environmental importance, thefate of copper in the investigated waters will bediscussed in some detail in the followingchapter.
6.2.5 The Behaviour of Copper
The statistical data analysrs showed that copperconcentrations rn water do not appear to besi gnificantly controlled by rnorganic factors.
Alkalinity and pH. adsorption to oxide surfaces(with the exceptron of alumrnium; and reducrngconditions (e.g. formatron of soluble copperamlne complexes) do not seem to have asrgnificant effect, on drssolved copper levels. Theabundance of organic complexing agents in theinvestigated Middle Fly floodplain waters maybe responsible for the observed behaviour ofdissolved copper. No coruelation was observedbetween DOC and copper levels in the floodplainwaters.
EO
o roo :oc roo ooo too ,Jo tJolrlilTooAtuminium i.rg/l
\c',f,_
b50no_or)
1A
36
It is evident that dissolved organic ligands, evenat comparatively low concentrations in waters ofthe Fly River system, are always present inexcess of trace metals which may becomecomplexed (although some complexing capacitymay be occupied by major cations like Ca andMg). In the Lower Fly River, downstream of theStrickland junction, measured dissolved coppervalues are still moderately high at 6 pg/l (Table4,6, annex) despite the massive admixture ofuncontaminated suspended matter from theStrickland River. It appears that the lowering ofdissolved copper levels in the Lower Fly ismainly due to dilution effects and thatadsorption to riverine particulate matter is ofsecondary importance.
Davis and Leckie (1978) tested the influence ofdissolved organic substances on copperadsorption. Certain organic ligands which formcoatings on suspended mineral particlesenhance the extent of trace metal adsorption,while others show opposite behaviour. Someorganic acids inhibit copper adsorption byforming soluble, stable complexes which keepthe netal in solution. When the complexingcapacity of dissolved organic carbon substancesis larger than the rate of adsorption to inorganicsurfaces, copper will remain in solution.
Sholkovitz and Copland (1981) also investigatedthe solubility and adsorption properties of anumber of trace metals in the presence of humicacids. Contrary to similar studies which wereperformed with synthetic Iaboratory waters,Sholkovitz and Copland used natural waterfrom a small stream in Scotland which drainspeaty soils. The properties of this water (DOC 7ng/I, pH 6.5, low conductivity) are similar tothose of the Fly River floodplain. The authorsdetected a coagulating effect on humic acids andtrace metals, particularly iron and copper, uponadding of only 0.5 mmolA of Ca, which isequivalent to 20 mg/l Ca.
The mean Ca concentration in mrxed waters ofthe Fly River inner floodplain is about 25 mgll.Coagulation of humic substances with adsorbedtrace metals may be an important process whencalcium-rich Fly River water mixes withfloodplain blackwaters. This is consistent withthe detection of elevated copper levels on the topof black, peat-like sediments sampled from lakebottoms far from direct Fly River in{luence. Theexperiments carried out by Sholkovitz andCopland (1981) also gave the result that therewas no precipitation of trace metals and humicacids when pH (starting point pH 6.5) waschanged in the range of 9.5 to 3, below whichhumic acids, Fe, Mn,'Cu, Ni and Cd began toprecipitate.
This behaviour is contrary to that predicted byinorganic solubility considerations. Complex-ation of the trace metals by dissolved organicmatter is the moet reasonable explanation.Organic copper complexes are known to beparticularly stable becauee of their favourableelectron configuration (Stumm and Morgan1981).
Fe and Mn in floodplain waters, despite theirchemical similarity, showed no significantcorrelation in any data set. Of the elementsinvestigated by Sholkovitz and Copland (1981),Fe>Cu>Ni>Cd (in decreasing order) showed thestrongest affinity for the dissolved humicsubstances, Mn and Co the least. The differingtendency of Fe and Mn to form complexes withdissolved organic carbon may explain themissing correlation in data from the Middle FlyRiver region.
In a copper adsorption experiment (spiking toyield 20 pgA Cu) with natural waters containingdilferent concentrations of suspended solids anddissolved organic carbon, Sholkovitz andCopland (1981) obtained results which suggestthat solubilization of Cu by dissolved organicligands, forming ultrafine colloids (< 0.01 pm), isa more important process than the adsorptiononto riverine particulate matter. Dven in watercontaining 100 mgil mostly inorganic suspendedmatter and 3 mg/l DOC, most of the copper waskept in solution as the pH increased from 4 to 9.
CSIRO of Australia (1989) performed mixingexperiments commissioned by Ok Tedi MiningLtd. with water from the Fly River and a
floodplain tributary. Mine derived sedimentwith high copper values was added to differentadmixtures. Total dissolved copper concent-rations increased with sediment admixture, thepH remained fairly constant. Dissolved copperspecies in the resulting solutions were analyzedby Anodic Stripping Voltametry 6SV). Themethod is used to determine labile trace metalspecies supposed to be present in the ionic, mostbioavailable form.
lnterestingly, between 30-50% of dissolvedcopper in the final test solutions was measuredas Iabile or "ionic" copper. Assuning that thecopper was present as dissolved organic species,the results point to great reactivity of humiccopper complexes in the Fly River system. Thisis consistent with more recent laboratory workundertaken by CSIRO on behalf of OTML(OTML 1994). Electrochemical measurementsof bioavailable copper in the Ok Tedi/FIy Riversystem gave the result that the fraction ofpotentially bioavailable copper is up to 5oo/o ofthe total dissolved copper concentration.
37
In the presumably unpolluted waters of theouter floodplain (it is difficult to establish themaximum intrusion range of Fly River water)copper was at or below the detection limit of 2pg[. In the Fly River, copper values were abouttenfold above this "background", which mayactually be much lower than 2 pg/l, i.e. 0.2 pgn.
Mixing of both waters should result in dilution.This is the case in most mlxed water samples,however in some waters copper concentrationswere much higher. Sample WLlT-4., which had adissolved copper concentration of 52 pgll in thefiltered and 106 pg/l in the unfi-ltered sample,was taken from a depression in flat swampyterrain about 150 m behind the low damparalleling the Fly River channel.
Water sampled from small pools and shallowwater courses in the periodically floodedgrassland sites usually gave high copper values.The water samples taken generally had iow pHand/or alkalinity. It appears that activeleaching of copper from deposited mine-derivedmaterial is responsible for the high dissolvedvalues observed.
In the floodplain swamps, redox conditionschange easily depending on the undulatingwater table which may result in trace metalmobilization. Because of the dense vegetationand the low rate of water exchange, solubleorganic chelates are abundant and mayfacilitate copper mobilization. The bufferingeffect of calcium disappears as the easily solubleelement is leached from the sediments. Becauseof the favourable conditions for trace metalleaching, even a thrn Iayer of deposited mine-derived material will be an important source ofcopper. Due to difficult access, only a fewsamples from the swamp sites were taken(water was sampled within a maximum distanceof one kils6sls1 from the main river channel). Itseems that the copper levels in floodplain watersinvestigated in the present study are biasedtowards low values (in samples from large lakesand tie channels) and are not representative forthe entire floodplain.
Where floodplain swamp waters wrth leachedcopper drain into lakes and the main river, theywill increase copper concentrations. This mayexplain why OTML (1991, 1998, 1994) reporrshigher dissolved copper levels at Obo ascompared to the upstream site at Nukumba,below the Ok TedilUpper Fly River con{luence.
A different type of water in which high traeemetal concentrations could be expected are thesamples called "floodplain seepage". Thesemoderately acidic waters percolate through thefloodplain sediments and drain spring-Iike intothe channels and rivers. The waters are highlyreducing and have a very high Fez+ and Mn2+content which is immediately oxidized to orangecoloured gels and flocs upon exposure toatmospheric oxygen. Although the floodplainseepage samples showed high Cd and pb levels,this was not the case for copper, which probablyremains in sulfidic binding in the sedimentbody.
Table l5 shows predictions based on computermodelling by OTML (1990) of variousenvironmental parameters in the FIy Riversystem in response to the impact of minedischarges. These additional environmentalmonitoring conditions were established toensure that the Acceptable Particluate Leuel of940 mg/l at Nuhurnba does not result ht actualetr,uiruunerttal dantage to tlrc Fly Riuer Systentbeyond th,e leuel achnlly specified ilt theprecLiction s (OTML I990).
The predictions resulting from theSupplementary Environmental Investigations(undertaken in 1986-89 by OTML) have beenestablished for testing whether or not the State'sconditions for environmental management of theFly River System and off-shore are met. Due toa number of reasons, there has been a non-compliance with monitoring conditionsbegrnning in 1990- Particularly the dissolvedcopper levels were much higher than expected.Measured values at the APL sitesKuambit/Nukumba, Obo and Ogwa have been ina steady increase between lgg0 and lggg(OTML 1994) contrary to the trend predicted bythe models. Revrsed prediction values for thekey environmental parameters were developedby OTML in July 1992 and again in December1993.
38
Toble 16: Pt-ed.ictiotts nto.de by OTML fit 1989 for hey enuironmental paraneters in' the Fly Riuersystem, and. reuised predictiotts for dissolued copper hr, 1992 and 1993 (OTML 1990, 1993'
1994).
a.. Po.rticu.late and. d.issolued copper and fish catch for the Kuambit/Nukunba, Obo andOgwa (OTML 1990).
19901991LWZ1993t99419951996ro 2008
1,36905715n5581581562
nvzn96938505g5ffi544
524 3 95401 2 118321 tt 35388 t 120n0 L t47NOL M7E3 L L47
17 359665946704 1194 1194 119
11 15
6?,8338429349349349
Source:pC\r -supplementarylnvestigatiou$YolFSppcndixB'-OCu -Supplementary Investigations, Vol.I' Figure 3'
Fisb catch -supptementary Investigatioos, vol 4 Appendixll'Figures tOa, 114 &.\?aandTable4A
b. Dissolued. copper predictiort's (pe/l), prouided to State ht' June 1992.
Year Nukumba Obo Oclra
l99lt99Z199319941995
t996
Error Estimate
r l (10.5)l3 (13.r)l4llllt2
+-78Yo
l5 (r4.2)r7 (r5.0)t7t5l5l8
+- SOVo
6 (s.4)6 (6.6)766I
+-85Yo
( ) atrnui (calcodar ycar) mcaas of obscnred '{-n
c. Reuised. predictiorts for dCu in Fly Riuer, and meon' da.ta for 1993 (OTML 1993).
{ ) Uppcr rnd lorvcr error estimatcs() Anrruel (srlcndrr -vc:tr) rnsrns of obscn'cd datit
Year I Nukumba Obo Oglva
1993
1994199i1996
1991r998
16 (4 - 28)(13.E)18 {4 - 12)r.r {3 - 25)r{ {i - 25}B {i -2i)tl (j-251
7 (3 - irl (17.6)
8(4-i2)4 {i - 25).
4(3-2r)i{i-25}I {i - 25'l
6.1 {l - 12} (7..1)
7.i (l - l4l6.7 lt - tzl6.6{l-12}6.r (r - ll)6.6{l-l1l
39
7. Biological lmpacts
The discharge of ore processing residues andmining wastes has significantly changed theaquatic environment of the Ok Tedi/Fly Riversystem. From the discussion in previous sectionsit can be concluded that there are three factorsof particular environmental concern: theincrease in particulate copper, in dissolvedcopper, and in suspended solids concentrations.The negative impact of each effect on the fluvialsystem is spatially di-fferent.
The massive increase in the suspended load ofthe Ok Tedi is mainly responsible for the declinein aquatic life upstream of the conJluence withthe Fly River, where fish populations andspecies diversity have been dramaticallyreduced (Smith 1991). The persistently highconcentration of suspended sediments in thewater interferes with gill respiration of fish andaquatic organisms, modifies the movement andmigration of fish and prevents successfuldevelopment of eggs and larvae. Heavy metalsin particulate and dissolved form, and toxicprocess chemicals like xanthates probably play aminor role in the adverse impact on the aquaticlife of the Ok Tedi River.
In the Fly River itself, a combined detrimentaleffect of suspended sediment, particulate anddissolved copper on the aquatic ecology is to beexpected. Monitoring undertaken by OTML(Smith 1991, OTML 1993, 1994) shows that fishpopulations in the Middle Fly River at Kuambit,immediately downstream of D'Albertis J unction,are continuously declining, in the range of 30-5oo/o (M. Eagle, pers. comm.). Statisticalanalyses gave the result that particulate copper(pCu) was the best negative correlate of fishcatches, but dissolved copper and suspendedsolids also have a negative effect. OTML (f994)speculates that the relationship between pCuand fish catch may either be attributed to anavoidance of pCu by fish or by a correlation ofpCu with a toxic fraction of dissolved copper.
Both total fish catches and the diversity of theaquatic fauna are affected. No clear negativeimpact of mine discharges on the abundance offish in the Middle Fly River downstream ofD'Albertis Junction can be established from thedata collected so far because of their highvariability. Fish biomass monitoring in the lastthree years has been strongly influenced by lowriver levels concentrating fish into the riverchannel as the floodplain dried, hence leading tohigh catches at the river sites. Clearly, the exactdetermination of fish populations (includingmigratory species) in a dynamic fluvialecosystem is a difficult undertaking since fishcatches are inJluenced by a number of factorswhich cannot be attributed to the mine waste,Iike periods of droughts and commercial andsubsistence fishing pressure. In addition, OTML(1994) admits that its database on fish biomassis limited with respect to baselne data andcomea to the conclusion that "changes betweenbefore and after mine start-up conditions cannotbe quantified for any site (in the Fly Riversystem)".
Considering the homogeneity of the Middle FlyRiver system and the fact that the key waterparameters influenced by the mine'e operation(dissolved and particulate copper and suspendedsolids) show little changes in the Middle FlyRiver reach between Kuambit/Nukumba andObo, negative effects on the fish populations inthe lower part of the Middle FIy region are to beexpected.
OTML (1993) report elevated copper levels inbody tissue of the catfish Arius benrcyi caught inLake Pangua, a deep oxbow lake. Arlus is abottom feeding omnivore. Aquatic invertebratesform the most important part of its diet, butdetritus/mud is also an important food item(I{are 1992). It is not clear whether the copperdetected in the fish was taken up via the bottomdwelling invertebrates, or directly from thecopper-rich sediment, the metal being releasedin the rntestinal tract of the catfish. In bothcases, it is evident that copper in particulateform on the lake bottom is bioavailable.
40
In the off-river floodplain sites of the Middle FIy
region, elevated concentrations of dissoived
copper may negatively affect aquatic life. The
floodplain plays an irnportant role in primaryproductivity to support fish stocks in the riversystem, and for the recruitment of fish- OTML(199f) states that the floodplain supports a
greater stock of fish than do oxbow and drownedvalley lakes. The Fly River channel is to a large
extent a fish tnigration route and a refugecluring clry periods. Subsistence and commercialfisheries target mainly the off-river water bodies
because of their high productivity. Although thevegetated flooclplain sites may not be inundatedover the whole year, fish invade rapidly into the
alluvial plain at higher water levels because ofthe abundance of food sources.
Animals at lower trophic levels, such as aquatic
invertebrates, and juvenile stages of fish are
known to have a high sensitivity to dissolved
copper. According to Moore and Ramamoorthy(1b84), sensitivity to copper is inversely related
to the age or size of an animal. A decrease in the
abundance of macroinvertebrates, which are atthe base of the food web, may lead to a decrease
in the overall fish population. Copper is a strong
toxicant to aqualic organisms but does not
biomagnify in the food chain. End consumers
like carnivorotrs fish show a much lower copper
body burden than benthic invertebrates likeburrowing mayfly larvae which feed directlyfrorn the contaminated substrate (Karbe 1988)'
The average copper concentration in mixedwaters of the inner floodplain is around 10 pg/l;
the Fly River water has about 17 pgil of copper'
These are concentrations which may be harmfulto biota. The applicable United States
Environmental Protection Agency (USEPA)
"Water Quality Criteria for the Protection ofAquatic Organisms and Llses" (1986)
recommends a maximum value of 6'5 pgn
(hardness 50 mg/l as CaCO'3, unfiltered water)
for the "chronic" 4-day average concentration,and 9.2 pg/l for the "acute" l-hour average
concentration. The Canadian Water QualityGuidelines (198?) are even more stringent, as
seen in Table 16.
Dissolved copper levels detected in mixed
floodplain waters of the present study are in the
concentration range which is reported in the
literature to be harmful to sensitive freshwateraquatic organisms. Clements et al' (i989) found
a significant decrease in total aquatic insect
abundance after 4 days of exposure to 6 pg/l of
copper in an outdoclr experimental stream'
The most sensitive species, a chironomid larva(midges, Diptera), was eliminated at 13 pg/l
copper after l0 days. Moore and Winner (1989)
also found out that benthic chironomid and
mayfly larvae show a high sensitivity todissolved copper. Burrowing mayfly larvae ofthe genus Plethogenesia (together withMacrobrachiurrr. freshwater prawns) were thedominant constituents of the macroinvertebratefauna in terms of biomass in the Fly River(OTML 198?). Both are important food items forthe local fishes. Toxicity of particulate copper inmrne wastes on mayflys has been proven by
bioassays undertaken by OTML in 1988 (OTML
1989).
Williams et al. (1991) report a 50% mortalityafter three days of exposure of the extremelysensitive tropical freshwater shrimp Carid'irt'o
sp. to 4 FSfi copper. Most studies on copper
ttxicity consider the free ionic speciee as the
most bioavailable form, and copper complexed
with naturally derived dissolved organic carbon(DOO as much less toxic or even non'toxic (e'g'
Flemming and Trevors 1989; Meador, 1991)'
Recent scientific work (Winner and Owen,
1991), however, has provided further evidence
that dissolved organic carbon also may enhance
copper toxicity. The authors used the alga
Ciia,tnyd.ontonas rein'hard,tii to test the
bioavailability and toxcity of organicallycomplexed copper in water from a freshwaterpond.
Toxic effects of dissolved copper on alga
de{lagellation and population growth were
observed at values above 12.2 pgl in naturalwaters with DOC concentrations varying from 5to 14 mg/l.
They found a positive correlation between DOC
and copper on alga toxicity and concluded thatlabile organic copper complexes may be
responsible for this effect, demonstrating that a
simple relationship between DOC concentrationan& copper toxicity cannot be established'
OTML (1994) has commissioned toxicity tests
with the freshwater green alga Chlorellaprotothecoides.
No reduction in algal growth rate occutred at
dissolved copper concentrations of L2 pgll, whichwas the highest concentration used in the tests'
Since copplr values measured both during thepresent study and by OTML in waters of the FlyiUver and its floodplain were much higher than12 $gn, it appears justified to repeat the tests
with copper concentrations of up to 50 pgll inorder to obtain more information on the species'
sensittvity.
41
Toble 16:Cantad,ian Guidelilws for the protectint, of freshwater aquatic life (CCREM tgST).
Plnmccr Gur<leline Commrntr
Inorganic paromctcrsAluminuml
.Antimony
Arscnic
Bcr-vllium
CNdEiurn
Copper
C:aridc
Dirsolvrd oxygen
Lron
be
Mcrcury
Nickcl
NitogenAruroaia (total)
NidteNitrercNimreraiaes
pH
Sclcuium
Silvtr
Thelliurn
7i,l.c'
Physical paramacr's
Temperarurc
Total surpcndcd solids
0.fi)5 mg,L-t pH<6.5r [Co:-[<{.0 mg.L-t;DOC<2.0 mg.L-r0.1 ng'L-t
IDT
0.05 ng'L- t
ID
0.! pg.l-t0.E FS.L- |
1.3 pg'l- t
l.t pg.L-l
pHa6.5i [Ca:-l>r.0 mg.L-r; DOC=].o E|8.L-l
Chlorim (.otrl r€sidud chlonnel 2.0 pg'L- '
Chromium
Hsrdncss 0-6O mg.L-r fCrCOrtHatdness 6&120 mg.L-t (C!CO1)Hardness ll&lE0 me'L-t (GCO3)Hardncss >ltO m-g.L-r (CeCOr)
lvtcasured bs anpcromertc or cquivalent mcthod
2.0 Pgl- t
3 Pg'L- t
3 Pg'l- t
3 Pg'L- t
4 pg'L-t
!.0 Pg'1-- I
6.0 mg'L- t
5.0 mg'l-t9.5 mc'L-l6.5 mg'L- t
0-3 mg'L- t
I Pg'!- t
3 pt'L-,.l pg.L-l7 ;rg.!- t
0.1 Pg'l- I
25 Ft'L-r65 pg'L-l
I l0 pg'L- t
150 pg'L- t
!.2 mg'L-r
0.01 mg'L-t To proreo fishTo proreet aquatic lifa iacluding rooplar*ron ard phyroplrntron
Hardness G60 mg'L- t (CeCOr)Hardness 6&130 mg-L-t (CaCO31
Haldncss l3GlE0 m-s.L-r {CaCOr)Hardncss >lE0 ms.L-r (CeCOr)
Ftec c-ranide as CN
"t'arm-*acr bioa - carly lifc sages
- othcr lih soges
Cold.watcr biota - carly life sogcs- othcr lifc ruqes
Hardacss G60 mg.L- I (CaCOr)H6r{nc!s 6G130 ng.L-t (CaCO5)
Hardnass l2Sl80 mg.L-t (C.CO3)Hardness >lt0 mg.L-r (CaCO1)
Hardacss S6O mg'L-t (CaCO3)Hadncss 6{}.120 mg.L-t (CICO3)Hardncss 12tr180 mg.L-t (CaCOr)Hardness >lt0 a1g.L-r (CaCO3)
pH 6.5: anpcrrtuc lOt (stc Tablc 3-12)1.3? mg.L- t pH t.0: ampcrerurt lfC0.06 utg'L- t
ID
6.5-9.0
I Fg'L- t
0.1 Pg'l-t
ID
0.03 mg'L- I
Cosccaczrroos that s.imuhc ptoliic ud goflh should bc rwidcd
Thcrmal addiuons should not oltcr lhcnflal stntificuion or rurnorsr dacs.:rcEd maltmum $'cekll,.lleB_qe tempcrlluEs. and ancced marimum shon_:efin rcmpenilurss rscc Sccrion .3-:.3.1-l)
inccasc of 10.0 Background tuspendcd solids =100.0 me.L-tt!g'L - |
rncrrrsc rrf l09t abovc Backgtouno susprnded solids >100.0 mc.L-tbackcround
I Coocenratroas of hcavy mctals reporad rs ronl menl in rn untilcnd samoic.: lD = insutficienr dua to recomrncnd a cuidcline,I Tcntarive guidclinc.
42
8. Conclusions
The following conclusions can be drawn from theinformations gathered in the present study:
1. Of the trace metals contained in the OkTedi mine waste, copper is of mainenvironmental concern because of its strongenrichment above background (about
twentyfold) and its relatively highgeochemical mobilitY.
2. The discharge of mining residues into theOk TedilFly River sYstem leade to a
substantial deposition of copper-richmaterial in the Middle Fly River floodplain,although most of the mining wastes carriedas suspended load finally reach the delta.Areas of standing water and vegetatedparts of the floodplain play an importantrole in the recruitment of fish and primaryproductivity. Hence, this part of the fluvialecosystem is particularly sensitive to mine-induced changes in the local environment.
3. The pollution by copper-rich material is notonly a problem of quantity, but also ofspatial distribution and the potentialmobilization of the trace metal' Depositionof mine-derived sediments in the FIy Riverfloodplain is highest in oxbow lakes.Because of the naturally high organiccarbon content in sediments, which isresponsible for reducing conditions, onlycopper in the uPPermost laYer (few
centimeters) of bottom sediments maybecome dissolved. When copper-richsediment is permanently covered by water,mobilization and bioavailability of themetal, except to bottom-dwelling inverte-brates, is low. However, when mine-derived sediments settle on extensive areasof the vegetated floodplain, the conditionsare quite different. Chemical and biologicalfactors facilitate the mobilization of copper.
Even a thin layer of copper-rich materialmay have a negative ecologrcal impact-
4. The way in which copper affects the aquaticcommunity is not clear. Dissolved organiccarbon substances, which are present inhigh concentrations in the Fly Riversystem, complex the metal and keep it insolution. Little is known about the bio-availablity and toxicity of these organiccopper species. Recent research has shownthat these compounds may exert toxiceffects comparable to the free ionic copperspecies.
The most sensitive biota to dissolved Cu arejuvenile stages of fish and aquaticinvertebrates which form the base of thetrophic web. Populations of larger frshspecies will only show a response after afull reproduction cycle has been completed.Thus, measurable negative elfects maydevelop with a considerable time lag.
The copper pollution in the Fly Riverfloodplain is of persistent nature. Evenafter the cease of deposition of copper-richsuspended load, the environrnentally detri-mental effects will continue to exigt. Thereis no mechanism to "de'toxifu" the alluvialplain. Erosion processes will only removedeposits in the main river channel and onthe banks immediately adjacent to it, and,
to a minor degree, along the channelsconnecting drowned valley lakes with themain river. The mine'derived materialdeposited in oxbow and drowned valleylakes, and in the floodplain swamps, willremain and may be covered bY lesg
contaminated sediments carried by the FlyRiver in the post-mining period' Howevet,when sedimentation rates in the floodplainreturn to pre-mining values, it may takecenturiee until copper'rich gediment
deposits are sealed by an unpollutedsediment cover.
The possibilities to mitigate the detrimentaleffects of the Ok Tedi mine waetes on theOk Tedi/Tly River system are limited when
the construction of tailings and waete
retention facilities is deemed uneconomicalby the mining company' In order to reducethe amount of metal discharged into theenvironment, the recovery of copper in themill, currently at around 85%, could be
increased. This may be Possible bY
installing more flotation cells, re'flotation oftailings, increase of the residence time ofore in the cells, improved control of grainsize in the flotation process, sulfidization ofnon-sulfide ores, and other optimisationstrategies. Thus, a recovery of 90% may be
achievable. The cut-off gpade for waste rockcould be lowered, which would decrease thecopper reaching the fluvial environment'These measures are most probably noteconomically viable; however, for environ-mental protective action, they should be
investigated thourougily by the miningcompany.
5.
43
L Acknowledgements
The authors of the study wish to thank theUnited Nations Enyironment Programme forfinancial support of the research project. Thestudy team is particularly indebted to Mr.Gerhart Schneider, Programme Offrcer with theWater and Lithosphere Unit at UNEPheadquarters in Nairobi, who offered promptassistance in solving all emerging problems.
David Mowbray of the Department ofEnvironmental Science of the University ofPapua New Guinea (UPNG) provided invaluablesupport througout the various stages of thereeearch project. The authors of the presentstudy wish to thank him and Dr. Ian Burrows,Head of the Biolory Department of UPNG, whoprovided working space and laboratory facilitiesduring the field work in Papua New Guinea.
Very special thanks go to Mr. Peter Gelau ofObo Station on the Middle Fly River, who helpedus in accomodation and transport problemsduring the various sampling campaigns, and Mr.Ben Kapi Mekeo, our reliable field guide andboat pilot. We also wish to thank the people ofAiambak, Bosset and Manda villages for thehospitality they have extended to us. We alsomay express our gratitude to Mr. Joseph Gabut.then with the Department of Foreign Affairs ofthe Papua New Guinea Government, forcontinued support of our research project. Wewish to thank Ok Tedi Mining Ltd. for analyzinga batch of water samples and further logisticalassistance.
44
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46
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47
Annex:
Table A1: Arwlytical results for sedintents front flood.plaht sites in the Midd,le and, LowerFly Riuer region, where no d,epositiort, of mine-deriued, material was d.etected., and. ofsedimetLts deposited ilr, the pre-mhirtg period. Sediments with. no grain size a.re <20 n.Statistics were calculated for the fraction <100 m.
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z fi: ; F: E5 E== E + a g : BuEuF s4 E ai E* EE n g ; ; : ;Ii!: ts: = s:r --: -; =E -=:- i q: F E6 HHP>. ?= '-: ..rd d= = 4 = ": ''! ? ai'iia
=ss33F33* **3s4s$3s
-z
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6Et
Table AI cotttitr.ued
o
I
j
F
3
0I
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ka
E
5€
E
€
a
a
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51
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5e e E =
E E EEE ==ii==R A g * =x = 3 = = = =-- sR3=I
= = F3 rn E E
= = s B== F=F=g s x 6. =A = E g
= H =e= gxd J; ;
3F= R R 3 F= R = x = F =-- gRagB p a g
=3 tr a a R a =n9
sbEEE E = E EE E g € E F g€g Eg+ -; -.i
=6= s s e 6= = e 3 g 5 rFs ==A^ - N a dN
RFS E R = x= s F R 5 = =-- ====- =+NN
-f d NvV- 'j
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=3: ::
EEE E E E EE E E S E E EEE EE--:: : .:vvv o o -' ---- J -q f,
= : ::: ::
=F= = = R R= S = = E F-- =RRSF 3 A e ex a = s g a R-- =BEEg E = = sE E = = E E 3-=
==3E= R = = == = g E a
= ss=
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E 5 R Si{tu =REEE F F F EE E = F € E Heg =H
3== a * E == = = g H = E==
=Ea3E E a F E3 a E € a a 8Ea aase= R F = F= F E = = H E-- sEFgF ; = E
=F € F € E F E== eFE=E = E F EE F = E E F EEE 8B
= = G G i;-_
==EeF F = = aa = E E a a aaB 8a==s s F = =- = = = E X E;<;< FEBJ 6-E:s.EgEl;;e5:E=:efTi=Eh f a = a F - i n t : ; TB'T g o J "r * g + i a +( 6
".i = - ; = = .. A *; g : E $ = E4l- E I 6 , ; ;' :^-.li F1 E : d E F : d ; il 7 He
ff; : E E f € =: 5 B F 4 r E**=" f I**= =
E E > Lw =
E ;S* Ee:,-:*.:.i F.! ': ? a =-
q =
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E
Table AI continu.ed
o
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dd
h
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5
5=
aa
aE
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EE ERE= F FFF = =EEEa3 €EFq E REF F EE=E
-e6q = =sg = 5==F
Node t:-a e 9PoFNdd
--gV V -U- --U?
g6 FgEE = €B€ G g€AC* 3 -:i
=v:+ v €'- F;=vi.-".? -1"?-:.: -: ':"?": : 3nF:novvvvovaooovovv
EE EEE+ E EEE E EEEEu:- ---<: - '-"-: I ----eovvvo<;cioovvvv
-- 6-a.t = >== = E=RS
bH AAg't g F=g fi 3=3=
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s= e=3d = 6=q E =ssE- =^-aa aaEa a E8E A 8388EF E=F= E E=F E ESSE
= Fi;td -
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RE =EEE F EFF E EE=3
BB ssAA a aE8 E E=aaBs =hl:= = E*a =
gBs=a3 aaaa e sEE e EsFqE= tr==F T === . R=s=
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:JJJr ..! -!d^r - -a-:JJ ;;;;; J JJ+ ={{- a<ss= S =*S S SSSS
aE
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Table AI cotltitLued
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d
>
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b
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9
a
4o
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E-o
g
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53
flE
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4*
€€q4
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9€
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Ne'
€€qa
a€
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TahlcAI cotltitund
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xTF = ssR.F
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EgH 53 BF?g
E',€g € EgeH5F E gg5*ErNNE E
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EEE E EEE+-* - 6--vvvvFtvv
E R= g tE= A9 ==;Si 'EE E$FtEi RR *R
,-1 4l
E€e a gaa 3E! 3AB:88 = SIPE eg ggiF- d- FF
EFE g =gE FE EgNo.n d Nh6 6F ai€
'--n H66 -- -F
aEE E a8a a8 8E'Belt A f:e!8 de 88
EFE = FE= FE FEE€a a a8a ta 8a:i:l= Sl g=a
== e=EFE a aB8 .a8 8afeFF3 E 3H= St= cF
EEOEBrrF T BB E6 6e1' n 66 oi tii{rD .d €fl 6o- = .As: g:!3 Fi1s A :- -* ;Ei8 -A -E E-&Ife . i6!! E€ B.5:_= : :'3q s= -ds.E=j 3 5s: E5 s:
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-+6.6
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tj .d-;
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si
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Toblc il!]: Atml.y1;col resrrlfs lor riuer banlt sed.inten'ts and suspen'd,ed solid,s from the
(Ippe,r Ok Tpct;ftiurr.. Sedi.nrcrr.ts utith. no grain size are <20 m. Statistics were calculated
l'or the |roctiort' <100 trt.
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gagSts*dh65<-
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s =Fe Ed==s =='ds= E=F EFEEE
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pfiFe= EE==E 6H.' =-3E3 ==R=F FFE EEEFE FE==s F=H HsE=a fixtieR FR= F€EFE E==E6
==2 =aaaF =EaEE EEE =eec=
F==A= aa3 =AB-E a3F=H EEF XEE:X SER=E EE= EEFE= FEEEa.tsEr:2a'ER.=aE8F.r€:8PE.i _ E
=g _EE.g Eae-€E:=;a R=-E-
E :=* qE=gF qEgiF4==:=djE*ss
oB
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Tablc A2 contituued..
oo60oQooH66:
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QGr Ald6<- €d
{.{*AT E€
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€-F
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6e,o 8eeoo +6Fdo €_oF9= 4€
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d-4v
eaaaagFH
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56
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To.ble AJ: Atw.lytical results for flood.plain sites in' the middle antd,I'ower F-Iy Riuer
Regiotr., where iepositiott of mhrc matLrial occured. Sed,iments with n'o groin siz'e giuen
u,ie <20 r,.- Sto.iists were calculated for the fractiorts <100 m otily.
E EEE'lcE jF
= EEEEz g
d6€a€
F ==EEF= EEHEs* =::=s
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F *=FE F
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57
Table A3 contirtued.
oo 9 9EFcEc EEE F= F: = E E eFcE E E.;33=5e EEE i= ie = =
E e5cl E E E56e-66€a+oq
g==ER dBg s= Hg a 3 = ==Rg G E<<-
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ada --
6 +_6F
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N
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G€6
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o*ES5= EE* =5 EE E E T ==SH = F
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Fs F3 € E .FRF h FNNNN
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= - 6€66
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Eiaaa€ Eaa Ea a3 € E F aaaa a 3Ea€=a s=H r3r == R 4 * FF== = E-66-- dci ].,
EEFSE =E=
F= EF E F = FEFF E F3s33= 8aa aa Ba 3 E F FER= g ==eE€€ SeG =ii RR s F. €otsNaJ - ;
=g€Eg =Fg Ea Ee e E F aEss 3 ad6F;He= =H= HR 3A A =
R A==F 5 =
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= F = = =E r e-E T= g E E E € € €E B F E1=E€i 5"_5 Ie. Fs. ii F .= .F-i E E 5
fE=ie: EiF =f sf : : : :j*=q g =
i*iqe :Ra :R :R = : -E=r --i ;;; =
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lll- l*l;fl-ll;ll:ll:ll=l
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I
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58
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g === s=-=
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==;';J d J -;.;.; eoee
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gEE=5 F E F€E EFE=
EE=s= = I =gF F*E=
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EEFEF F F EEE =AE=FE==F E
= EFE EE=E
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aF= eeEa
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6FEli si E
E -l;a EE e i * S E 6e E
g"i"f Z E fr'E ti=eT
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Table AJ cotttirr'ued.
?
z
o
o-o
5t
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a
--e5
o
g
eeF:-:-EeciEEeN66No6
=s€==;=H€SER=
d@oaeF:
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6Fa€6O
rF5
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g==cB=
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EE==gEB=enH=EF=EEEA=A=EE
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EFA=EF=g= a a a=ESFs=-3E E3-.=-T=s=.E EL*l;" "i, _eF F:8 E.-:=EE=-
oo9
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59
Table A3 contiltued.
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O-16-€6tsA@a\
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6+N€ 66-F No F=Bg€st€;ia i;s
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9ddP d6F6Fdi
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+
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d
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T,ab1e Ai, A6olryses af th,e waters af tlve ftlt River f,l,oodpl,a'in. fuIeiliww-rneanw ottd,
stard,ard, ttreui;a-tiip, otily gi,;nen uhere ap,prop-rioate. NF rtearus wtfulteted' uatar sam9fi4
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