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 Reserved in CTR pending agency consultations Conceptual Model –Importance of chemical speciation Uncertainties –Risk assessment, future loads, Alviso Slough Dr. Khalil E. Abu-Saba Dr. Scott Ogle Rocks!

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 The Tone : What captures the imagination… WILD (Wildlife Habitat)

…isn’t always the issue. Exposure Health Deficient Toxic Human Dietary requirements =  g / day Human NOEL = 850  g / day 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.

San PabloSouth BaySuisun Dr. Scott Ogle Rocks! Things Change… Changes in San Francisco Bay diving duck tissue selenium concentrations over time. Base Graphs courtesy of the Regional Monitoring Program/San Francisco Estuary Institute.

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

dissolved selenate dissolved selenite dissolved organo- selenium particulate elemental selenium pythoplankton / particulate organo- selenium ParticlesSolution But why? Chemical Speciation

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

Load Reduction Dr. Scott Ogle Rocks!

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

Another Key Uncertainty