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Localized Mercury Bioaccumulation Study Presented to the SFEI 20 February 2008

This study evaluates mercury bioaccumulation in bioindicator organisms to assess environmental risks posed by a wastewater treatment plant effluent. Results show significant effects on aquatic organisms near the outfall. Valuable insights for local decision-making. Study conducted in relation to the San Francisco Estuary Institute in 2008.

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Localized Mercury Bioaccumulation Study Presented to the SFEI 20 February 2008

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  1. Localized Mercury Bioaccumulation Study Presented to the SFEI20 February 2008

  2. Outline • Project Overview • Results • Conclusions • Outreach Component • Next Steps

  3. Approximate location of SRWTP outfall diffuser

  4. Study Design’s (Null) Hypothesis: [MeHg] in bioindicator organisms (clams) does not vary according to space (upstream vs. downstream site) or time (i.e., between different sampling periods).

  5. “Hot spot”, Defined Technical: The null hypothesis is rejected because of a measurable effect of SRWTP effluent. ~ AND ~ Policy: Evidence of localized environmental risk that is so clear and convincing that a reasonable decision maker would conclude that some action must be taken.

  6. SRCSD Reg. Larry Walker Assoc. UCD – F. Schilling UCD – D. Slotton Applied Marine Science SRCSD Lab Caltest Lab Studio Geochimica Lab Cindy Brown Brock Bernstein Robert Mason Project Team Tech. Adv. Comm.

  7. * * * * * * * * * * * * * * * * * * * * * * * * Conceptual Model Water Surface Exposure Biouptake/ Bioaccumulation Sorption/ Desorption River Flow Deposition/ Erosion Sorption/ Desorption Methylation/ Demethylation Diffusion Streambed Sediments • Fish Diet • Pelagic: • Small Fish • Zooplankton • Benthic: • Clams • Plants • Worms • Clam Diet • Organic Carbon • Phytoplankton • Phaeophytin • Zooplankton • Bacteria • [MeHg] Factors • DO • Organic Carbon • TSS • pH • Salinity • Redox Potential • Sulfate • Reactive Mercury • Sulfides • Nutrients (N, P, Si) • Complexation Factors • Mercury • Organic Carbon • TSS • DO / Redox Potential • pH • Salinity • Sulfides Effluent

  8. MonitoringStations in the 5-mile Study Reach GB R-1 E-001 R-2b R-3 RM44 Monitoring Stations

  9. Fish – Locally in Fall Proposed TMDL Goal

  10. Ham. City (80 mi) Feather R Fish – Sac. R. Watershed Scale Colusa Drain 50 ng/g Prickly Sculpin, Fall 2006 Cache Ck Veteran’s Bridge Yolo Bypass American River Garcia Bend Putah Ck River Mile 44 TMDL WQO = 30 ng/g in fish < 50 mm long

  11. (90 mi) (40 mi) Silverside Fall 2006 Mercury Spatial Distribution, following high runoff and flooding winter and spring

  12. Effluent Mercury – Local Effects Summary Distance from Outfall 1) MeHg_sed, Transp. Clams, Resident Clams, Silversides, Juv. Blk. Bass ~10% 2) MeHg_wtr 3) THg_wtr, THg_sed, Sculpin

  13. Models Developed [1] Unexpected negative relationships.

  14. The evidence presented by this study argues that: SRWTP effluent contributes about the same amount of mercury to bioaccumulation as expected from effluent load estimates.

  15. The evidence presented by this study argues that: Methylmercury in aquatic organisms near the SRWTP outfall is not outstanding compared to other areas of the Sacramento River Watershed and the Delta.

  16. Technical: The null hypothesis is rejected because of a measurable (i.e., statistically significant) effect of SRWTP effluent. ~ BUT ~ Policy:Is evidence of localized environmental risk so clear and convincing that a reasonable decision maker would conclude that some action must be taken locally?

  17. Fishing Areas GB R-1 E-001 Shore fishing R-2b R-3 RM44 Monitoring Stations

  18. 5. Next Steps

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