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Mercury in SF Bay The 8-Minute Conceptual Model California Regional Water Quality Control Board San Francisco Bay Region RMP Annual Meeting May 4, 2004.

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Presentation on theme: "Mercury in SF Bay The 8-Minute Conceptual Model California Regional Water Quality Control Board San Francisco Bay Region RMP Annual Meeting May 4, 2004."— Presentation transcript:

1 Mercury in SF Bay The 8-Minute Conceptual Model California Regional Water Quality Control Board San Francisco Bay Region RMP Annual Meeting May 4, 2004 Richard Looker

2 2 The 30 Second Conceptual Model Bacteria in wetlands, mudflats and sloughs Mercury in sediment Methylmercury available for bioaccumulation Mercury Discharges (Elemental and Inorganic) Methylating Regions-- 1. Mass budget3. Bioaccumulation 2.Transformations & Transport

3 Significance and magnitude of loads? Variability and Predictability of Loads? Details of the active sediment layer? Inputs ~ 1200 kg/yr: Outputs ~ 1700 kg/yr: ~ 100 kg Hg in Water ~ 60,000 kg Hg in Active Sediment ~ 10,000 kg Hg In Air Shed (20 km top) 1. Mass Budget 15 cm Active Sediment

4 Where is methylation happening? (controlling factors?) Transport details? (erosion, sediment movement?) Hg in Water 2. Transformations & Transport Me-Hg in Benthos Me-Hg in Sediment Hg in Sediment DepositionEvasion Export BurialErosion Me-Hg in Water Me-Hg in Fish Import Active Sediment

5 What is the food web structure? What are food web concentration patterns? 3. Bioaccumulation (Me-Hg concentrations shown relative to water) Me-Hg in Water Me-Hg in Sediment ?? Eggs: 6000

6 6 Wildlife and Fish Tissue are Indicators of Impairment Too much Hg in fish – TMDL target is 0.2 ppm Too much Hg in bird eggs – TMDL target < 0.5 ppm Indicators for Management – Concentrations in small and large fish – Bird egg concentrations – Prey items for birds, fish – Sediment Me-Hg, Total Hg

7 7 What RMP Can/Could Do to Help Gather risk management information (5 yrs.) – Fish consumption patterns among humans – Contamination patterns Track food web concentrations (5 yrs.) Track bird egg concentrations (5 yrs.) Investigate significance of sources (5 yrs.) – Relative bioavailability (from chemistry) – Residence time issues (from transport) Keep on sampling water, sediment, fish

8 8 What RMP Could Do To Help (but needs some help to do it) Coordinate Hg-related research (ASAP) – Disseminate results – Ensure intercomparability of results – Ensure research addresses management needs There is currently no coordination between large number of research efforts. We will not have another chance like this in terms of resources so there is a desperate need to make the most of this opportunity.


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