Acidification in southern Norway : seasonal variation of aluminium in lake waters

Jens Petter NilssenZoological Institute, University of Oslo, Blindern, Oslo 3, Norway

Keywords: aluminium, southern Norway, acidic lakes, pH, organic content, liming

Abstract

Total aluminium, pH and water colour were measured over two years in three lakes of different pH in anarea undergoing anthropogenic acidification in southern Norway . Al content decreased in Ca-rich lakes nearthe coast, but also with increasing organic content of the lakes . Seasonal variation was pronounced in themost acidic lake . Al concentration seems virtually independent of pH, suggesting that it is in the form oforganic complexes, at least in the two most coloured lakes . Precipitation processes affecting fish metabolismin the acidic lakes with high Al content may have caused the frequent lack of success in liming lakes in thisarea. Similarily, humic acidic lakes with organic complexed Al still carry considerable fish biomass .

Introduction

Acid rain is seriously affecting large areas ofCanada, Norway, Sweden and the U .S .A. (Jensen& Snekvik 1972 ; Gran et al. 1974; Almer et al. 1974 ;Likens & Bormann 1974; Beamish 1974 ; Beamish&Harvey 1972; Braekke 1976 ; Nilssen 1980) . The ef-fects of acid rain are best demonstrated on smallerrivers and lakes, while the terrestrial system showsno documented relationship to increasing fallout ofacids (Braekke 1976) . The leaching of Al from thesoil to rivers and lakes increases considerably withincreasing acidification of the rain (Braekke 1976 ;Wiklander 1977 ; Likens et al. 1977 ; Almer et al.1978; Dickson 1978 ; Cronan & Schofield 1979) .Below a pH of 4 .5 Al exists predominantly as A1 3+in distilled water or water with low organic content,while at a pH of 4 .5-6.3 neutral Al(OH) 3 will domi-nate together with a lesser share of other hydrolysedAl ions (Dalal 1975) . With pH changing rapidlyfrom low to higher values, Al ions that are notcomplexed with organic molecules precipitate andseem to interfere with fish metabolism . This maycause mass mortality in fish cultures (cf. Muniz &

Hydrobiologia 94, 217-221 (1982) . 0018-8158/82/0943-0217/$01 .00 .© Dr W. Junk Publishers, The Hague . Printed in The Netherlands .

Leivestad 1979). Such changes in Al species may bethe reason for the fish kills observed in Norwegianrivers with low solute contents during spring(Braekke 1976 ; Muniz & Leivestad 1979) . Due toflocculation processes (e .g . Hornstrom et al. 1973),acidified lakes exhibit comparably lower colourand consequently lower organic contents than lakesthat have neutral pH (Almer et al. 1974), theirAl-complexing capacity is therefore smaller (Pi-onke & Corey 1967) . Remarkable pH declines dur-ing the ice free period seem characteristic for manyacidic lakes due to negligible buffering capacities(Nilssen et al., in prep .) . The recovery phase follow-ing such a temporary pH drop can be deleterious tofish (cf . Almer et al. 1978 ; Muniz & Leivestad 1979)and probably other aquatic taxa (cf . Sennichsen1978), because Al is readily hydrolysed . Seasonalvariation in pH, organic solutes and Al in lakewaters may therefore be of great importance inassessing the responses of fish and other aquaticbiota to ambient water quality .

2 1 8

The lakes investigated

The lakes investigated are shown in Fig . I andTable 1 shows some important chemical data (part-ly from Nilssen 1980) . Differences in the solutecontents can be ascribed to the different geochemis-try in the catchments (Nilssen 1980) . Lakes H andOK are situated in an area which has experienced agradual lowering of pH in precipitation over thelast 30 years . pH in lake H has remained constantsince 1973, while pH in lake OK has decreased 0 .4(Nilssen 1980) . Bicarbonate is seldom present inthese lakes . pH stability may be due to the bufferingcapacity and the neutralizing ability both in thecatchments and the lake itself by soil cation ex-change (cf. Cronan & Schofield 1979), organicmolecules in the water (cf . H ornstrom et al. 1973) orthe various Al species (Almer et al. 1978) . Theheadwater lakes in the area (Fig . 1) are poor insolutes; Si is very low and Al contributes consider-ably to the cation budget . The organic content isconsiderable in lake F, suggesting that most Alexists as organic ligands, which partly may be thesame in lake OK as well (cf . Johnson 1979) . In themost acidic lake H, with lowest organic content, Alis probably present mainly as A1 3 + ( cf. Dalal 1975 ;Johnson 1979), especially during spring (cf. Dris-coll et al. 1980) .

Material and methods

Samples were taken at depths of 1, 3, 5, 7, 10, 15,20 and 25 m (depending on lake depths) every 1-3weeks during April-October, and every 4-5 weeksthe rest of the year. pH was measured within 4 hafter sampling ; Al samples were frozen. The ana-lyses include only total Al, since pH is changing and

Fig . 1 . The lakes surveyed. Lake F (Fievann) is situated onmarine deposits, lake OK (Ostre Kalvvann) on medium acidicpre-Cambrian bedrocks (so-called Bamble formation), and lakeH (Heilandsvann) on strongly acidic pre-Cambrian bedrocks(so-called Telemark formation) . Also see Table 1 .

organic Al ligands change their qualities duringfreezing and thawing . Al was determined with acolorimetric method using pyrocatechol violet atpH 6 .2 and read at 585 nm. The threshold value is10 µg/ 1 . The other chemical methods are describedin Nilssen (1980) .

Results and discussion

The results are shown in Fig . 2 (also see Table 1) .In 1977 the summer weather was warmer and more

Table 1 . Characteristic parameters of the investigated lakes and the precipitation at the meterological station Treungen due northwest oflake Heilandsvann . Precipitation data from Seip & Tollan(1978) . Mean values for 1977 and 1978 at intervals indicated in Material andmethods given in mg/ l . According to Aberg & Rodhe (1943) the water colour measured as mg/ I Pt was suggested to be correlated to theorganic content (dissolved organic matter) of the sample. Water colour of the precipitation was measured near lake H by the author .

Org. cont .mg/I Pt pH tot-Al Ca Mg Na K NH, SiO, HCO, Cl SO4 NO 3

Fievann 90 7 .3 0 .100 28 .0 3 .5 11 .0 1.8 0 .05 0 .8 50 .0 14 .0 17 .0 0 .25Ostre Kalvvann 30 5 .0 0 .175 2 .8 0 .8 2 .3 0 .7 0 .03 0 .3 0 3 .5 9 .0 0 .10Heilandsvann 15 4 .6 0 .250 1 .3 0 .3 1 .2 0 .5 0 .05 0 .2 0 1 .5 5 .0 0 .15Precipitation -0 4 .3 <0.010 0 .6 0 .3 0 .6 0 .1 0 .47 0 0 .8 11 .3 1 .67

HEILANDSVA NN80

9.0

6.0

1 .0

OSTRE KALVVANN FIEVANN

J M M J S N

J M M J S N

stable than in 1978 . July 1978 was extremely wet,which led to much lower pH values in the epilim-nion of the poorly buffered lakes H andOK. In lakeF, pH was relatively stable, but a decrease in bicar-bonate was observed in the upper water . Al contentdecreases in lakes towards the coast, and decreaseswith increasing organic content in the surveyedlakes (Fig. 3) . Seasonal variability of Al seems mostpronounced in lake H . A decrease from higher win-ter levels to lower spring and summer levels seemsto take place in April and May in all lakes . Adecrease in Al at this time of the year may be ageneral phenomenon in acidified waters (cf . Hen-riksen 1976; Skartveit & Gjessing 1979) . No pro-nounced short-term changes of Al were recordedwithin the period investigated . During spring thereoccurred first a general increase in Al by increasedmobilization of soil Al, and then a decrease bydilution ; but sampling dates are too infrequent toshow if this is a general phenomenon . Johnson et al.(1969) recorded an increase in Al with higher waterdischarge in Hubbard Brook. Short-time samplingin other acidic areas during spring has not revealedextensive changes in Al content, although changesare observed in H+ (Henriksen 1976 ; Skartveit &Gjessing 1979) . These changes in H+ are more pro-nounced in low-order rivers than in lakes whereshort-term changes are masked by considerable wa-ter volumes (cf. Henriksen 1976) .

J M M N

8 .0

6.0

z .09.0

6.0

.3

.1

2 1 9

Fig. 2 . Seasonal changes of pH and total Al in the three lakes . pH is included from 1 m( )and 7 m(---), meant to represent epilimnionand hypolimnion respectively . Note the scale on Fievann pH 1978 . Al is measured by integrating samples from above and below thethermocline . Usually 1, 3 and 5 m samples constitute the epilimnion . -: epilimnion, - - : hypolimnion .

As shown in Fig . 3, dissolved Al concentration isvirtually independent of pH, an impossibility ifAl(OH) 3 saturation were involved . The lakes seemundersaturated with respect to metastable Al(OH)3 .The high acidities of the lakes are probably ex-plained by the absence of Al(OH) 3 , neutralizing thestrong acids of acid rain . All dissolved Al, especiallyin lakes F and OK, is probably in the form ofmolecular organic complexes probably reflectingpodzolidation processes .

The total Al content of the waters seems relative-ly stable in spite of large changes in pH, CO 2 andorganic contents (colour) (see Fig. 3); these arepresumably the most important factors affecting Alspecies distribution. Al solubility changes, howev-er, over this range of changing water quality (cf .Pionke & Corey 1967; Dalal 1975) . With decreasingpH below 4 .5, Al solubility increases rapidly, butwith increasing pH the Al species are present in aprecipitated form . Short-term pH changes havebeen observed in both lakes H and OK (Hagenlund& Simonsen, unpubl . data), and the recoveryphases following such pH drops may affect nega-tively many aquatic taxa (cf. Sennichsen 1978). Inlake F and to a lesser extent lake OK where the formof Al is probably mainly as organic Al ligands, theeffect of fluctuating pH on the aquatic biota isconsequently much smaller . This may explain whyacidic lakes with a high organic content are the last

pH 1977 pH -1977 H

197~7~

AI -1977

1978

nI

AI - 1978 ••1

PI - 1978

220

too

50 -

10 .

5

H' peq/l

.5 .

.1 .

5 10

50

100

Al Neq/l

Aberg, B. & Rodhe, W ., 1942 . Uber die Milieufaktoren in eini-gen sudschwedischen Seen . Symbol. Bot . Upsalien 5(3) :1-256 .

Almer, 8., Dickson, W ., Ekstrom, C ., Hornstrom, E . & Miller,U ., 1974 . Effects of acidification on Swedish lakes . Ambio 3 :30-36.

Almer, B ., Dickson, W ., Ekstrom, C . & Hornstrom, E ., 1978 .Sulphur pollution and the aquatic ecosystem . In : Nriagu,J . O . (Ed .) Sulfur in the Environment, pp. 271-311 . J . Wiley .

Beamish, R . J ., 1974 . Loss offish populations from unexploitedremote lakes in Ontario, Canada as a consequence of atmos-pheric fallout of acid . Wat . Res . 8 : 85-95 .

Fig. 3 . Upper panel: pH plotted against Al (calculated as AI3+ ) .

Beamish, R . J . & Harvey, H . H ., 1972 . Acidification of the LaLower panel : organic content (as water colour in mg Pt/ I) plot-

Cloche mountain lakes, Ontario, and resulting fish mortali-ted against Al . Samples taken at I m depth . All lakes included .

ties. J . Fish . Res . Bd Can. 29: 1131-1143 .

5

10

Al Neq/I

50

100

to lose their fish populations ; many of these lakesare still important fishing areas although their pHhas always been well below 6.0 (cf. Lande 1972 ;

Nilssen 1980) .

Acidification of lakes and the associated die-outof salmonids (salmon, brown trout, char), coregon-ids (whitefish) and percids (Eurasian perch) are themost serious threat to nature in Norway (cf .Breekke 1976) . Much effort has been devoted toliming (CaCO 3 ) clear-water acidic lakes, but resultsare inconclusive, frequently because the effects ofacidic water on fish metabolism, aside from pHitself, are poorly known . Liming of freshwater lakesin the present study area seldom succeeds in raisingthe pH of the water much above 5 .5 (0 . Vestal, I .Knudsen, pers. comm.), and the bicarbonate con-tent stays low (Nilssen, unpubl . data) . Short-termpH changes, together with low buffering capacities,low organic contents and high Al contents of theselakes may have caused the frequent lack of successin liming lakes in this area, by placing serious meta-bolic stress on fish species .

Acknowledgements

I am grateful to Charles T. Driscoll, EvilleGorham, Ronald J . Hall, Merete Johannessen,Noye B . Johnson, Helge Leivestad, Gene E . Likens,Ivar P. Muniz and Richard F . Wright for readingand commenting on the paper . I also thank myNorth American colleagues for correcting the En-glish language, and Morten Nicholls for the Alanalyses .

References

Brxkke, F . H . (Ed .), 1976 . Impact of acid precipitation on forestand freshwater ecosystems in Norway. SNSF-report FR6/76: 1-lll .

Cronan, C . S . & Schofield, C . L ., 1979 . Aluminium leachingresponce to acid precipitation : effects on high-elevation wa-tersheds in the northeast . Science 204 : 304-306 .

Dalal, R . C ., 1975 . Hydrolysis products of solution and exchan-geable aluminium in acidic soils . Soil Sci . 119 : 127-131 .

Dickson, W ., 1978 . Some effects of the acidification of Swedishlakes . Verh . int . Verein . Limnol. 20 : 851-856 .

Driscoll, C . T . Jr ., Baker, J . P ., Bisogni, J . J . & Schofield, C . L .,1980 . Effect of aluminium speciation on fish in dilute acidi-fied waters. Nature 284 : 161-164 .

Gran, O ., Hultberg, H . & Landner, L ., 1974 . Oligotrophicationa self-accelerating process in lakes subject to excessive

supply of acid substances . Ambio 3 : 93-94 .Henriksen, A ., 1976 . Vann- og nedborkjemiske studier i Langt-

jernfeltet i perioden 5 .mai 1973 til 30 .juni 1975 . SNSF-pro-ject TN 25/76 : 1-53 .

Hornstrom, E ., Ekstrom, C ., Miller, U . & Dickson, W ., 1973 .Forsuringens inverkan pa vastkustsjoar. Inform . Inst .Freshwat. Res . Drottningholm 4 (1973) : 1-97 .

Jensen, K . W . & Snekvik, E ., 1972 . Low pH levels wipe outsalmon and trout in southernmost Norway. Ambio l :223-225 .

Johnson, N . M ., 1979 . Acid rain : neutralization within the Hub-bard Brook ecosystem and regional implications . Science204:497-499 .

Johnson, N. M ., Likens, G . E ., Borman, F . H ., Fisher, D . W . &Pierce, R . S ., 1969 . A working model for the variation instream water chemistry at the Hubbard Brook experimentalforest, New Hampshire . Wat . Resour. Res . 5 : 1353-1363 .

221

Jones, J . R . E ., 1964 . Fish and River Pollution . 203 pp .Lande, A ., 1972 . Fiskeded og surt vann . Fauna (Oslo) 25 :

105-110 .Leivestad, H . & Muniz, I . P ., 1976 . Fish kill at low pH in a

Norwegian river. Nature 259 : 391-392 .Likens, G. E. & Bormann, F . H ., 1974 . Acid rain: a serious

environmental problem . Science 184 : 1176-1179 .Likens, G . E ., Bormann, F . H ., Pierce, R . S ., Eaton, J . S . &

Johnson, N . M ., 1977 . Biogeochemistry of a forested Ecosys-tem. Springer Verlag, New York . 146 pp .

Muniz, I . P . & Leivestad, H ., 1979 . Langtidseksponeringav fisktil Burt vann . Forsek med bekkereye Salvelinus fontinalisMitchill . SNSF-project IR 44/79 : 1-32 .

Nilssen, J . P ., 1980 . Acidification of a small watershed in south-ern Norway and some characteristics of acidic aquatic envir-onments. Int . Revue ges . Hydrobiol . 65 : 177-217 .

Pionke, H . B . & Corey, R . B ., 1967 . Relation between acidicaluminium and soil pH, clay and organic matter . Proc. Soil .Sci . Soc . Am . 31 : 749-752 .

Seip, H . M. & Tollan, A ., 1978 . Acid precipitation and otherpossible sources for acidification of rivers and lakes . Sci .total Environ . 10: 253-270 .

Skartveit, A . & Gjessing, Y ., 1979 . Kjemisk materialbalanse ogkjemiske endringer i sne og avlepsvann i Tovdal, vAren 1977 .SNSF-project IR 43/79 : 1-44 .

Sennichsen, T ., 1978 . Toxicity of a phosphate-reducing agent(aluminium sulphate) on the zooplankton in the lake LyngbySo. Verh. int . Verein . Limnol . 20 : 709-713 .

Wiklander, L ., 1977 . Forsurningproblemet for mark och vatten .11 . Skogs- o . Lantbr .-akad . Tidskr . 116: 93-108 .

Received 12 November 1981 .