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University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

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

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University of Ljubljana, Slovenia Jožef Stefan Institute, Slovenia

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  1. 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 Jožef Stefan Institute, Slovenia • ELOISE 2004

  2. Mercury mine in Idrija: • 127.000 tonsof 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 Mercury cycle in the wider Idrijaregion and the Gulf of Trieste • ELOISE 2004 • ELOISE 2004

  3. 1 4 6 7 9 11 12 13 14 17 D6 AA CZ WHO limit Hg in the river system and fish From: Hines et al.2000; Horvat 2002; Horvat 2004 • ELOISE 2004

  4. Gulf of Trieste: Annual mass balance of total Hg and MMHg • ELOISE 2004

  5. Modelling approach • Hydrodynamics (flow / circulation) • Transport and dispersion of pollutants • Biogeochemistry (sources, sinks, reactions - transformations) • ELOISE 2004

  6. Interaction between the models Input data Boundary conditions • Meso-scale aquatic models • Mediterranean Local scale models • sources • erosion • Regional scale aquatic models • Idrijca and Soča River • Gulf of Trieste • ELOISE 2004

  7. M e R i M o d Erosion model P C F L O W 3 D Models • 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 • ELOISE 2004

  8. Results: input data for the river model possible remediation measures EROSION MODEL and Hg release GIS-layer based model Data – layers: topography, geology, pedology, land cover, land use, slope, precipitation, runoff. Measurements: Hg • ELOISE 2004

  9. Modelling results for PT scenario • ELOISE 2004

  10. 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

  11. 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 • ELOISE 2004

  12. 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

  13. Calibration & validation – transport • Autumn – winter conditions, high discharge (flood events) • Simulation of an observed flood event • 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…) • ELOISE 2004

  14. 15.000 tons • ELOISE 2004

  15. 322 ng/l 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 3 • ELOISE 2004

  16. Transformation processes (MMHg) • 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

  17. air-water exchange • methylation • demethylation • reduction • oxydation • exchange with the • bottom sediment Hg MODULE PCFLOW3D ADVECTION-DISPERSION MODEL FOR MERCURY with transformations river loads sea currents sea bottom processes PCFLOW3D-ST SEDIMENTATION MODEL CONCEPT OF THE 3D WATER MODELING SYSTEM (MARINE ENVIRONMENT) PCFLOW3D-HD thermohaline forcing wind tidal forcing river inflow momentum HYDRODYNAMIC MODEL • ELOISE 2004

  18. CONCEPT OF THE WATER MODEL (MERCYMS) air-water exchange deposition deposition dry wet dry wet demethylation methylation HgII MMHg reduction oxydation settling & resuspension Hg0 settling & resuspension diffusion diffusion decay & settling decay & settling bottom layer release METH =Kmeth* Hg2Di DEMETH =Kdemeth* MHgDi RED =Kred* Hg2Di OXY =Koxy* Hg0 dissolved particulate Equations: plankton gaseous • ELOISE 2004

  19. Reactions & evasionsimulations HgT, MMHG, Hg0 Preliminary results Surface layer; ng/l • ELOISE 2004

  20. Evasionrate ng/m2/h Preliminary results Surface layer ng/m2 • ELOISE 2004

  21. Average concentr. of Hg in MED.SEA: 0.57 ng/l or 2.84 pM Surface: 2.51*10**6 km2 Volume: 3.60*10**6 km3 ATMOSPH.-OUT = 60 t Rivers 13.7 t IN = 10 t (?) Bosporus IN = 0.3 t Gibraltar OUT = 10.1 t To sediment = 14t Point sources 2.3 t Total IN: 33.8 t Total OUT: 70.1 t (- Sediment 14 t) MEDITERRANEAN IN = 7.5 t 2040t = IN MASS BALANCE OF Hg IN THE MEDITERRANEAN • ELOISE 2004

  22. 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…. Hg(2+), Hg0, MMHg, DMHg… • ELOISE 2004

  23. Conclusions • Different 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

  24. 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

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