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San Francisco Bay Wetland Reconstruction and Mercury Biogeochemistry – How to do the right thing?

San Francisco Bay Wetland Reconstruction and Mercury Biogeochemistry – How to do the right thing?. Dr. Herbert Fredrickson, Dr. Victor McFarland, Dr. Elly Best, Dr. Greg Kiker, Dr.Robert Jones, Dr. Gui Lotufo, Dr.Rod Millward and Mr. Richard Price

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San Francisco Bay Wetland Reconstruction and Mercury Biogeochemistry – How to do the right thing?

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  1. San Francisco Bay Wetland Reconstruction and Mercury Biogeochemistry – How to do the right thing? Dr. Herbert Fredrickson, Dr. Victor McFarland, Dr. Elly Best, Dr. Greg Kiker, Dr.Robert Jones, Dr. Gui Lotufo, Dr.Rod Millward and Mr. Richard Price U.S. Army Engineer R&D Center, Environmental Laboratory, Waterways Experiment Station, Environmental Laboratory,Vicksburg, MS 39180-6199 Dr. Holger Hintelmann and Dr. Brian Dimock Chemistry Dept., Trent University, Peterborough, Ontario, Canada.

  2. Hamilton Army Airfield and Bel Marin Keys Hamilton Army Airfield China Camp

  3. Hamilton Army Airfield • HAAF will require <10 M yd3 of dredged material

  4. China Camp State Park – Reference Site Spartina foliosa Salicornia virginica

  5. Table 1. Total mercury levels reported in San Francisco Bay sediments in the 1997 Regional Monitoring Program Annual Report (SFEI 1999). Estuary Reach Location  THg Concentration, g g-1, dry weight Rivers Sacramento River San Joaquin River 0.04 0.53 Northern Estuary Honker Bay Grizzly Bay Pacheco Creek Napa River Davis Point Pinole Point San Pablo Bay Petaluma River 0.26 0.29 0.05 0.39 0.04 0.23 0.36 0.48 Central Bay Red Rock Point Isabel Richardson Bay Horseshoe Bay Yerba Buena Island 0.05 0.28 0.25 0.15 0.23 South Bay Alameda Oyster Point San Bruno Shoal Redwood Creek Dumbarton Bridge South Bay Coyote Creek 0.27 0.23 0.24 0.32 0.33 0.51 0.78 Southern Sloughs San Jose Sunnyvale 0.18 0.16 Estuary Interface Standish Dam Guadalupe River 0.14 1.08 Mercury Levels & Relevance Relevance THg µg/g Earth’s crustal average 0.08 SF Bay sed. baseline 0.06 1997 SF Bay sediment < 40% fines 0.25 40-100% fines 0.43 SF Bay average fish 0.09- 0.27 SF Bay striped bass 0.42 Fish action levels USDA 1.0 FL & WI 0.5 MN 0.16 SF Bay 0.23

  6. 1,000 100 10 1.5 1.0 MeHg (ng/g) HAAF/China Camp Freshwater Wetlands Marine & Estuaries Lakes Rivers Regression 95% Prediction Interval 0.10 0.01 350 0.001 0.10 1.0 10 100 1000 10000 100000 1000000 THg (ng/g) Benoit et al., 2003 Aquatic Systems Produce Methylmercury THg and MeHg in surface (0-4 cm) sediments from various wetlands • Only a loose relationship between THg and MeHg levels (log – log plot). • Despite history of mining level of THg and MeHg are median among contaminated sites. • However, potential for a 10X increase/decrease in MeHg levels.

  7. CALFED Stakeholders Workshop 8-9 October 2002, Moss LandingMarine Laboratory Research questions to be answered • What are the present levels of MeHg in SF Bay wetlands with respect to biota, sub-habitats, and location within the Bay? • What are the rates of MeHg production? • What factors control MeHg production? Can these be managed? • Are some wetlands larger mercury exporters than others? • Can we model/predict the effects of wetland restoration on MeHg production and export?

  8. Hamilton Army Airfield Initial conditions 2005 Ten year projection 2015 Initial sample locations Fifty year projection 2055

  9. Survey of THg and MeHg in HAAF sediments Total mercury in sediments grouped by location. Boxes are medians and interquartile range. Whiskers are 10th and 90th percentiles. Triangles are outliers. Data shown are from the dry season. • THg averages 0.3 µg/g in soils, consistent with other reports. • MeHg levels are highly variable.

  10. 1. What are the present levels of MeHg in SF Bay wetlands with respect to sub-habitats ?

  11. The Effects of Wet and Dry Seasons An important driver for most Bay functions. San Rafael Average Temperature and Rainfall 10 90 Precipitation Minimum Temp 80 Maximum Temp 8 w 70 60 6 50 Temperature, 40 Rainfall, Inches 4 30 o F 20 2 10 D 0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec • Relative MeHg levels are 3X greater on average in the wet season.

  12. 1. What are the present levels of MeHg in SF Bay wetlands with respect to biota ? High Primary Production – Hallmark of Intertidal Wetlands • Vascular Plants Annual Rates of Biomass Production • 0.5-1 kg/m2 above ground • 0.5-1 kg /m2 below ground • Epipelon – high production/quality Salicornia virginica epipelon Spartina foliosa

  13. 1. What are the present levels of MeHg in SF Bay wetlands with respect to biota ? Marsh compartment HAAF China Camp THg MeHg THg MeHg ng/g dw (SD) ng/g dw (SD) ng/g dw (SD) ng/g dw (SD) Bare Mud 378 (89) 1.78 (1.80) 327 (17) 1.56 (1.12) 7.42 (3.72) 288 (12) Epipelon 296 (51) 1.27 (0.25) Spartina foliosa Mud 407 (30) 1.35 (1.42) 371 (59) 2.22 (1.29) Roots 260 (62) 4.24 (0.54) 175 (32) 5.59 (3.75) Stems 18 (-) 1.08 (-) 28 (-) 2.65 (-) Leaves 39 (25) 0.90 (0.35) 17 (10) 0.68 (0.36) Salicornia virginica 304 (36) 314 (42) 1.11 (0.79) 2.39 (1.68) Mud 330 (170) 3.03 (1.22) 2.28 (-) Roots 123 (-) 114 (-) 1.28 (-) Stems 203 (-) 1.29 (-) 18 (5) 24 (12) 1.01 (0.58) Leaves 0.95 (0.24) • Relative to ~ 2% Std. Analytical Error, THg & MeHg levels are variable. • Levels of MeHg in plant roots are higher than surrounding sediment. Entry into food web?

  14. 1. What are the present levels of MeHg in SF Bay wetlands with respect to biota ? Decomposing macrophyte litter generates MeHg

  15. 1. What are the present levels of MeHg in SF Bay wetlands with respect to biota ? Mercury Bioaccumulation Factors (BAF) Hemigrapsus oregonensis MeHg Geukensia demissa THg Nassarius obsoletus

  16. 1. What are the present levels of MeHg in SF Bay wetlands with respect to biota ? Dr. Joy Zedler’s Study (1997) of Tijuana Estuary d34S can differentiate seawater from rainwater

  17. Crabs, Arthropods, Insects Fish Mollusc Spartina Salt Pond Algae Salicornia 1. What are the present levels of MeHg in SF Bay wetlands with respect to biota ?

  18. CALFED Stakeholders Workshop 8-9 October 2002, Moss Landing Marine Laboratory Research questions to be answered • What are the present levels of MeHg in SF Bay wetlands with respect to biota, sub-habitats, and location within the Bay? • What are the rates of MeHg production? • What factors control MeHg production? Can these be managed? • Are some wetlands larger mercury exporters than others? • Can we model/predict the effects of wetland restoration on MeHg production and export?

  19. 2. What are the rates of MeHg production? Microbial Production of Methylmercury Food Web Biomass MeHg Me200Hg 199Hg2+ Add O2 + Eh SRB - Eh 5-72 hr. 5-72 hr. Hg2+bioavailable Me199Hg 200Hg2+ Measure ? ? Hg2+not bioavailable

  20. 200 – 500 μM SO4-2 Gilmour and Henry 1991 4. Are some wetlands larger mercury exporters than others? Petaluma River Sonoma Baylands Hamilton Army Airfield China Camp

  21. SUMMARY • Quantitatively most important pools: • Sediment THg • Sediment MeHg • Tidal water • Plant biomass • Quantitatively most important processes: • Methylation rate • Demethylation rate • Sedimentation rate • MeHg entry into and magnification up marsh/Bay food webs • THg & MeHg flushing – marsh/Bay • Atmospheric flux

  22. Thanks Eric Poulsen, Brian Dimock, Olivier Clarisse John Brezina, Jim Cole

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