Measurements of Mercury Concentrations and Loads in a Large River System Tributary to San Francisco Bay, California, USA Nicole David, SFEI Lester McKee, SFEI Item #3

Study Design Hg, PCBs, PAHs, oc-pesticids, PBDEs, Se conc. during high flow events Continuous sediment measurements Quantify pollutant load estimates Include DAYFLOW data from DWR Item #3

Daily Delta Discharge 90% of the flow occurred in 51% of the days Item #3

Daily Sediment Load Net transport occurred on just 70 days or 1.6% of the time Item #3

Flow Patterns and Mercury Concentrations Item #3

Flows between 0 and 150,000 cfs Flows between 150,000 and 370,000 cfs

Particulate Hg Concentration over Time Item #3

Loads from the Delta Item #3

Hg Sources Watershed (Urban, Ag, etc.) Air Deposition (indirect and direct) Historic Item #3

Comparison of Yield Rates Worldwide 1 Negro and Solimões River, Brazil 2 MacKenzie, Canada 3 Sacramento River, CA 4 Potamac, MD 5 Headwater Mississippi, MN 6 Minnesota River, MN 7 São Francisco, Brazil 8 St. Croix River, MN 9 Blue Earth, MN 10 Rum River, MN 11 Le Sueur, MN 12 Sudbury River, MA (past superfund site) 13 Sudbury River, MA 14 Catchment in Sweden Item #3

700 kg/yr +/- 50% wet deposition WS MI 262 kg/yr +/- 37% 154 kg/yr +/- 50% in mixed WS Mining ? Item #3