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Selenium in San Francisco Bay

Selenium in San Francisco Bay. Status: Possibly Impaired Standards: Relevant Beneficial Uses: Fishing, wildlife habitat, rare and endangered species Water Quality Objectives 5 ppb (total in water) – attained everywhere but Alviso Slough

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Selenium in San Francisco Bay

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  1. Selenium in San Francisco Bay • Status: Possibly Impaired • Standards: • Relevant Beneficial Uses: • Fishing, wildlife habitat, rare and endangered species • Water Quality Objectives • 5 ppb (total in water) – attained everywhere but Alviso Slough • Narrative for bioaccumulation – much improvement 1986 - 2002 • Reserved in CTR pending agency consultations • Conceptual Model • Importance of chemical speciation • Uncertainties • Risk assessment, future loads, Alviso Slough Dr. Khalil E. Abu-Saba khalila@lwa.com www.cleanestuary.org Dr. Scott Ogle Rocks!

  2. The Tone: What captures the imagination… WILD (Wildlife Habitat) The story of migrating birds is the story of a promise, a promise to return. They fly, often thousands of miles, beset with danger, for a single reason: to survive. Their migration is a fight for life. Winged Migration http://www.werc.usgs.gov/scoter/maps.html

  3. Human Dietary requirements = 40 - 300 g / day Human NOEL = 850 g / day Health Toxic Deficient Exposure …isn’t always the issue. • Original Basis for Impairment: • Selenium in diving ducks exceeded risk assessment thresholds for people who hunt and eat ducks • OEHHA Consumption Advisory as published in (older) CDFG game regulations • Technical basis published in Fan et al. (1989) COMM: “Uses of water for commercial or recreational collection of fish, shellfish, or other organisms in oceans, bays, and estuaries, including, but not limited to, uses involving organisms intended for human consumption or bait purposes.

  4. 2002 2002 2002 1986 1986 1986 San Pablo South Bay Suisun Things Change… 2002 1988 Changes in San Francisco Bay diving duck tissue selenium concentrations over time. Base Graphs courtesy of the Regional Monitoring Program/San Francisco Estuary Institute. Dr. Scott Ogle Rocks!

  5. …sometimes for the better. Selenium concentrations in white sturgeon, 1986-2000. Base Graphs courtesy of the Regional Monitoring Program/San Francisco Estuary Institute. Dr. Scott Ogle Rocks!

  6. But why? Chemical Speciation dissolved selenite dissolved selenate particulate elemental selenium pythoplankton / particulate organo-selenium dissolved organo-selenium Particles Solution

  7. Biogeochemical Transformation transport transform Ag drainage Sac. R. bioaccumulate Refineries 90% load reduction by 1998 Ocean bacteria Ocean dissolved selenite dissolved selenate bacteria (sulfate inhibited) Evasion particulate elemental selenium pythoplankton / particulate organo-selenium dissolved organo-selenium Dimethylselenide clams Invasive Hyperaccumulator birds and fish people

  8. Load Reduction Dr. Scott Ogle Rocks!

  9. Selenium Reservoir in San Joaquin Valley B A 1,000,000 - 160,000,000 kg Se 50,000 kg 2,000 - 20,000 kg Se / yr C E D Key Uncertainties 1) Why is Alviso Slough so high in Selenium? 2) What is future irrigated agriculture load?

  10. Another Key Uncertainty

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