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Mathematical modelling of erosion, mercury transport and transformations from Idrija to the Gulf of Trieste Dušan Žagar, Ana Knap, Rudi Rajar, Gregor Petkovšek, Milena Horvat, Branko Kontić, Jože Kotnik, Nives Ogrinc, Matjaž Četina University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia ELOISE 2004 EUROCAT & MERCYMS

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EUROCAT & MERCYMS. Mathematical modelling of erosion, mercury transport and transformations from Idrija to the Gulf of Trieste. Dušan Žagar, Ana Knap, Rudi Rajar, Gregor Petkovšek, Milena Horvat, Branko Kontić, Jože Kotnik, Nives Ogrinc, Matjaž Četina. University of Ljubljana, Slovenia - PowerPoint PPT Presentation

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Page 1: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Mathematical modelling of erosion, mercury transport and transformations

from Idrija to the Gulf of Trieste

Dušan Žagar, Ana Knap, Rudi Rajar, Gregor Petkovšek, Milena Horvat, Branko Kontić, Jože Kotnik, Nives Ogrinc, Matjaž Četina

University of Ljubljana, Slovenia

Jožef Stefan Institute, Slovenia•ELOISE 2004

EUROCAT & MERCYMS

Page 2: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Mercury cycle in the wider Idrijaregion and the Gulf of

Trieste

•ELOISE 2004

Mercury mine in Idrija:

•127.000 tons of Hg extracted in 500 years

•37.000 tons of Hg “lost”

•over 12.000 tons entered the river system

•about 2500 kg/yr enters the river system

•about 1500 kg/yr transported to the Gulf of Trieste

•ELOISE 2004

Page 3: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Hg in the river system and fish

•ELOISE 2004

From: Hines et al.2000; Horvat 2002; Horvat 2004

1 4 6 7 9 11 12 13 14 17 D6 AA CZ

MeHg in Fish

0

500

1000

1500

2000

2500

3000

1 2 3 4 5 6 7

Location

MeH

g [

ng

/g]

WHO limit

Page 4: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Gulf of Trieste: Annual mass balance

of total Hg and MMHg

Gulf of Trieste: Annual mass balance

of total Hg and MMHg

•ELOISE 2004

Page 5: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Modelling approach

Hydrodynamics (flow / circulation)

Transport and dispersion of pollutants

Biogeochemistry (sources, sinks, reactions - transformations)

•ELOISE 2004

Page 6: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Interaction between the models

Local scale models

Meso-scale aquatic models•Mediterranean

-

Regional scale aquatic models• Idrijca and Soča River

• Gulf of Trieste

•ELOISE 2004

Input data

Boundary conditions

• sources• erosion

Page 7: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Models

•ELOISE 2004

Erosion model (Idrija region): Hg

release 2.500 kg/year

River model (Idrijca and Soča):

transport and transformations

Marine model (Gulf of Trieste): Hg

input 1500 kg/year

Page 8: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

EROSION MODEL and Hg release

Results: input data for the river

model possible remediation

measures

A i

junction(J)

Idrij

ca R

iver

GIS-layer based model

Data – layers: topography, geology, pedology, land cover, land use, slope, precipitation, runoff.

Measurements: Hg

•ELOISE 2004

Page 9: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Modelling results for PT scenario

•ELOISE 2004

Page 10: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Results and findings from EROSION MODEL

Present situation: annual Hg release to Idrijca River: 2500 kg

PT scenario: change in land use and elimination of hot spots: decrease of annual Hg release to 1445 kg

Possible reduction: 42 %

Cost: 28 mil. €

•ELOISE 2004

Page 11: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

1-D model MeRiMod structure

already used for the Carson River (NV, USA)adapted for Idrijca and Soča Rivers (parameters – measurements)real time unsteady-state simulations

W ASP5

RIVMOD MERC4

- hydrodynam ics- sedim ent transport

- ve locities- depth- shear stress

- m ass balance equations(advective and d iffusive

transport)

- concentrations of various po llu tants- bed load concentrations- suspended load conc.

- m ercury speciation andkinetic transform ation

- concentrations of inorganic m ercury (H gII)- concentrations of m ono- m ethyl m ercury (M M H g)

•ELOISE 2004

Page 12: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

MeRiMod modelling cases:

• Case 1 : Flood waves – transport (autumn, spring)

overbank deposition in flood-plains bank erosion historical mass balance of the catchment improvement of input data for PCFLOW3D

• Case 2 : methylation in the river system (summer)

•ELOISE 2004

Page 13: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Calibration & validation – transport

Point 1: within ± 30 %Point 2: within a factor of 4 (15 t model, 4.7 t estimated)scenarios for historical Hg mass balance of the catchment (Q500, Q200…)

Calibration poin t 1

Calibration poin t 2

Autumn – winter conditions, high discharge (flood events)

Simulation of an observed flood event

MeRiMod - Calibration Q100

050

100150200250300350

400450500550600650700750

0 12 24 36 48 60 72 84 96

Time [h]

Flow [m3/s] Suspended sed. (statistics) [g/m3] Susp. sed. (model) [g/m3]

•ELOISE 2004

Page 14: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

•ELOISE 2004

To the G ulf2160 t

Evasion30 t

Sed im entation1830 t

15.000 tons

Page 15: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Transformation processes (HgT)

summer conditions (low discharge 10 - 25 m /s)

comparison to measurements (Hines et al., 2000)

agreement mostly within a factor of 5

qualitatively questionable

Total Hg in water

0

10

20

30

40

50

0 20000 40000 60000 80000 100000 120000

Distance from Idrija [m]

ng

/l

HgT HgT(diss) Measurements HgT

322 ng/l

3

•ELOISE 2004

Page 16: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Transformation processes (MMHg)

MeHg in water

0.00

0.20

0.40

0.60

0.80

1.00

0 20000 40000 60000 80000 100000 120000

Distance from Idrija [m]

ng

/l

MeHg(T) MeHg(Diss) Measured MeHg(T)

K = f (water temp., Ph)

many BGC parameters still missing

comparison to measurements (Hines et al., 2000)

agreement within a factor of 3, qualitatively good.

met/dem

•ELOISE 2004

Page 17: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

CONCEPT OF THE 3D WATER MODELING SYSTEM (MARINE ENVIRONMENT)

thermohaline forcingwindtidal forcingriver inflow momentum

HYDRODYNAMIC MODEL

PCFLOW3D-HD

river loads sea currentssea bottom processesPCFLOW3D-ST

SEDIMENTATION MODEL

• air-water exchange• methylation demethylation• reduction• oxydation• exchange with the bottom sediment

ADVECTION-DISPERSION MODEL FORMERCURY with transformations

Hg MODULEPCFLOW3D

•ELOISE 2004

Page 18: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

CONCEPT OF THE WATER MODEL (MERCYMS)

demethylation

methylationMMHgHgII

Hg0

deposition deposition

dry wet dry wet

reduction

oxydation

bottom layer release

decay & settling

decay & settling

air-water exchange

settling & resuspension

settling & resuspension

dissolved

particulate

plankton

gaseous

diff

usi

on

diff

usi

on

METH = Kmeth * Hg2DiDEMETH = Kdemeth * MHgDiRED = Kred * Hg2DiOXY = Koxy * Hg0

Equations:

•ELOISE 2004

Page 19: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Reactions & evasionsimulations HgT, MMHG, Hg0

Preliminary results

Surface layer; ng/l

•ELOISE 2004

Page 20: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Evasionrate

ng/m2/h

ng/m2

•ELOISE 2004

Preliminary results

Surface layer

Page 21: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

ATMOSPH.-OUT = 60 t

Gibraltar OUT = 10.1 t

IN = 7.5 t

IN = 10 t (?)

Bosporus IN = 0.3 t

Point sources 2.3 t

Rivers 13.7 t

To sediment = 14t

MEDITERRANEAN

2040t = IN

Surface: 2.51*10**6 km2

Volume: 3.60*10**6 km3

Average concentr. of Hg in MED.SEA: 0.57 ng/l or 2.84 pM

Total IN: 33.8 t

Total OUT: 70.1 t

(- Sediment 14 t)

MASS BALANCE OF Hg IN THE MEDITERRANEAN

•ELOISE 2004

Page 22: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

Calibration - validation

Connecting reaction coefficients and environmental parameters (data from measurements – deep sea and coastal)

artificial intelligence

(machine learning)

“simple” statistical

methods

T, DO, ChlA, NOx,TSM, wind, radiation….

•ELOISE 2004

Hg(2+), Hg0, MMHg, DMHg…

Page 23: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

ConclusionsDifferent processes are important in different compartments and scales

Understanding and modelling of complete Hg cycling is needed

Erosion: remediation measures were determined

River system: transport in agreement with measurements, BGC processes somewhat worse

Marine: verification done, calibration in progress

Coupled models are useful tool in analysing Hg cycling processes in the environment

•ELOISE 2004

Page 24: University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

POSSIBLE MEASURES to reduce toxic effect of MMHg in the area

Reducing Hg transport within the river system: diminish erosion near Idrija (forestation, elimination of hot spots) dredging of sediments along both rivers construction of new reservoirs (?) – or elimination (?)

Reducing methylation (conditions): to improve water quality in the river sytem and the Gulf – WW

treatment, reducing mariculture, aeration (?) dredging of bottom sediment to reduce the source of MMHg -

technically possible, very expensive, where to put Hg contaminated sediment (?)

Administrative measures – prohibition of fishing, mariculture…

•ELOISE 2004