1. Collaborative Meeting on Modeling Mercury in Freshwater Environments January 19, 2006 Niagara Falls, NY Overview of Watershed and Water Body Models for Mercury used by the US EPA Christopher Knightes USEPA / ORD / NERL / ERD Athens, GA

2. Wet Deposition Hg 2+ Dry Deposition Hg 2+ (p,v) Evasion (Hg 0 ) Resuspension Runoff and Erosion Litterfall and Throughfall Hg 0 Watershed Processes Settling Hg 2+ MeHg Diffusion Dry Deposition Burial Mercury in Watersheds And Water Bodies Food Web Transformation Ground Water? MeHg Hg 2+

3. Primary 1 and Support Models for Analysis of Mercury Fate available from EPA - Athens SERAFM – Mercury Risk Screening Model WCS (MLM) – Watershed Loading Model GBMM – Grid-Based Watershed Loading Model WhAEM2000 – Groundwater Flow Model WASP7 – Water Body Pollutant Fate Model EFDC – Water Body Hydrodynamic Model BASS – Aquatic Food Web Model 1 Simulates mercury explicitly.

4. Watershed Mercury Models Watershed Characterization System, Mercury Loading Module – WCS MLM  Current available model  Grid soil calculations, sub-watershed loading resolution  Simple hydrology, erosion, mass balance  Provides yearly-average concentrations, loads Grid-Based Mercury Model – GBMM  Projected Availability: January 2006  Fine grid resolution  Simple wetland and tributary transport and transformation algorithms for mercury  Provides daily concentrations, loads  Future incorporation into BASINS toolkit

5. Water Body Mercury Models SERAFM:  Process-based, Steady-State Lake/Pond Model  Enhanced version of IEM-2M from Mercury Report to Congress  Stand-Alone model developed for Risk Assessors  Incorporates Watershed Runoff and Erosion, Mercury Cycle Chemistry, Bioaccumulation, and Wildlife/Human Risk Values  Provides yearly-average concentrations, loads  Serves as a Repository for Updates in Mercury Science and Modeling WASP7 and WASP7 Mercury Module:  Dynamic, Process Modeling Framework  General design for modeling contaminant fate and transport in surface waters  Compartment Modeling Approach, Lakes/Ponds/Rivers  Incorporates Mercury Module  Is being updated to incorporate SERAFM Science  Model architecture is being updated and improved

7. WASP Mercury Module Volatile Exchange of Hg(0) Watershed and Atmospheric Loads of Hg(II) and MeHg State Variables Hg(0) Silt Hg(II) Sand MeHg Biotic Solids Methylation Demethylation Oxidation Reduction Burial Point Source Loads of Hg(II) DOC

8. Mercury Watershed/Water Body Links Watershed Models WCS-MLM GBMM WARMF Water Body Models WASP SERAFM Hydrodynamic Models EFDC DYNHYD EPD-RIV1 Bioaccumulation Models BASS FCM-2 External Spreadsheets ASCII Files Windows Clipboard Atmospheric Models

9. Brier Creek Mercury Modeling: WCS-MLM and WASP7 HgII in Soil Tributaries reduction, evasion Atmospheric Wet and Dry Deposition reduction, volatilization Impervious Surface volatilization export Water Surface runoff export runoff and erosion sediment layer MeHg Hg(II) Hg 0 Silt, POM water column Sand Burial Leaching

10. Mercury Reduction Benefits Analysis: Changes in Mercury Concentrations and Evaluation of Response Times for Mercury Emission/Deposition Reductions Applications of SERAFM, WASP, WCS, and BASS Eagle Butte, South Dakota Pawtuckaway Lake, New Hampshire Lake Waccamaw, North Carolina Brier Creek, Georgia Lake Barco, Florida

12. Summary of Ecosystem Characteristics ParameterPawtuckaway Lake, NH Lake Waccamaw, NC Lake Barco, FL Eagle Butte, SD Brier Creek, GA Watershed Area 50 km 2 217 km 2 04.2 km 2 2,190 km 2 Lake Area3.64 km 2 34.7 km 2 0.12 km 2 0.19 km 2 n/a Watershed/ Lake Ratio 13.76.3022n/a Residence Time 165 days241 days0012 days StratificationYesNo Depth5m2.3m3.7m2.0m0.3 – 2.0 m pHNeutralAcidic Alkalinen/a Trophic StateDystrophicMesotrophicOligotrophicEutrophicn/a Total Hg Dep20.7 ug/m 2 /yr 29.2 ug/m 2 /yr 31.5 ug/m 2 /yr 19.8 ug/m 2 /yr 26.8 ug/m 2 /yr

13. Predicted vs Observed Fish Concentrations Observed vs. predicted fish mercury concentrations in model ecosystems at steady state with no change in atmospheric loading. Straight line represents 1:1 relationship between observed and modeled results.

14. Representative Changes in Fish Concentrations in Response to Emission/Deposition Reductions

15. Site SERAFMWASP FastMediumSlowFastMediumSlow Eagle Butte, SD34661116 Pawtuckaway Lake, NH80125>180244469 Lake Waccamaw, NC3612101517 Brier Creek, GAn/a 4982123 Lake Barco, FL142845n/a Sensitivity Range of Response Times

16. Current and Historical Applications by NERL-ERD Staff Steamboat Creek and Wetland Mesocosm near Reno, NV  Scott Brown (MS Thesis at UNR) under advisement of Chris Knightes (SERAFM) Sudbury River, MA  Chris Knightes (SERAFM, WASP7) Cheyenne Sioux Reservation Ponds, SD  John Johnston (SERAFM) Five Representative Ecosystems: Brier Creek, GA; Lee Dam, SD; Pawtuckaway Lake, NH; Lake Barco, FL; Lake Waccamaw, NC.  Robert Ambrose, Elsie Sunderland, Chris Knightes, John Johnston (WCS-MLM, SERAFM, WASP7, BASS) Vermont & New Hampshire Lakes  Chris Knightes (R-MCM) Ogeechee, Canoochee, & Brier Creek River Basins, GA  Tim Wool, Chris Knightes & Robert Ambrose (WCS-MLM, WASP7) Ochlockonee, Savannah, St. Mary’s, Satilla, Suwanee, GA  Tim Wool & Robert Ambrose (WCS-MLM, WASP7); Craig Barber (BASS) Everglades, FL  Robert Ambrose, Craig Barber, Rochelle Araujo (WASP5, BASS)