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From Micro to Macro: A view from downstream

From Micro to Macro: A view from downstream A synthesis of MeHg science from the Yolo Bypass and SFB-Delta. Modified from Parks et al. Science 2013. Lisa Windham-Myers 9/26/13 EPA Workshop, San Francisco, CA. MeHg. Tributary MeHg. Agricultural Lands / Delta Islands. Urban & WWTPs.

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From Micro to Macro: A view from downstream

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  1. From Micro to Macro: A view from downstream A synthesis of MeHg science from the Yolo Bypass and SFB-Delta Modified from Parks et al. Science 2013 Lisa Windham-Myers 9/26/13 EPA Workshop, San Francisco, CA

  2. MeHg TributaryMeHg Agricultural Lands / Delta Islands Urban & WWTPs Wetlands Pore WaterExchange & Diffusion OpenChannel Hg MeHg bacterial methylation Where can we control MeHg loading to delta? Surface Sediments Figure from Michelle Wood, CVRWQCB

  3. Where can we control MeHg loading to delta? Agriculture Type Managed Wetlands (85% seasonal)

  4. What Controls MeHg Production? MeHg Production Potential (MPP) = kmeth x Hg(II)bio Seasonal Wetlands Moderate MPP High MPP • Periodically flooded • Vegetated High Hg(II)-methylating bacteria activity (kmeth) Moderate MPP Low MPP Low Low High Hg(II)bio Concentration

  5. Wetland Mercury Cycling Bioaccumulation Transport Production

  6. Key findings of synthesis(Windham-Myers and Ackerman, 2012) • Hydrologic Control • Slowing water flow increases rates of storage and degradation of MeHg more than production. • BUT • Slowing water concentrates surface water MeHg and enhances in situ bioaccumulation in fish. • Permanent Wetlands • Rates of MeHg storage and degradation may exceed processes of MeHg production (net sink). • BUT • High soil carbon (peat) may produce more MeHg than they remove (net source). • Seasonal Wetlands • Rewetting of dried wetlands regenerates biogeochemical species that enhance MeHg production. • reactive Hg • ferric iron (FeIII) • sulfate (SO4) • labile carbon • Flood-up of dried wetlands can generate an initial pulse of MeHg from sediment to surface waters. • TEMPORAL VARIABILITY in matrix concentrations can be orders of magnitude • “Hot moments” drive annual patterns of MeHg production and export in seasonal wetlands. • Diel patterns in surface water – lower concentrations during daylight, higher concentrations at night – may be important in shallow vegetated habitats, due to dominant effects of photodemethylation and/or downward advective storage of MeHg through transpiration.. • Biota MeHg concentrations vary over time, and breeding season is when wildlife is most vulnerable. • SPATIAL VARIABILITY can relate to different initial conditions or management practices. • Total Hg concentrations are often poorly correlated with MeHg concentrations. • Soil organic matter is associated with MeHg in wetlands and irrigated agriculture. • Wetlands can be a MeHg sink or source based on the relative loads of sourcewater and tailwater.

  7. Yolo Bypass: Pulse of MeHg in surface water upon flood up Alpers et al. 2013

  8. Yolo Bypass: Pulse of MeHg in surface water upon flood up Alpers et al. 2013

  9. Yolo Bypass: Wetlands are all MeHg sources in winter except Permanent Wetland (which is a sink year-round). Source Sink Bachand et al. (b) 2013

  10. Yolo Bypass: Seasonal wetlands discharge dissolved Hg (0.45 mm) Alpers et al. 2013

  11. Yolo Bypass: Seasonal wetlands primarily discharge dissolved MeHg (0.45 mm) Alpers et al. 2013

  12. Temporal Variability Surface water concentrations change over 24hour diel cycle Photodemethylation and Transpirative Demand Effects are greatest during summer, leaf-on conditions See Fleck et al. 2013

  13. Temporal Variability Loads: “we need movies, not snapshots”. Browns Island: Continuous monitoring using FDOM (Bergamaschi et al. 2011)

  14. Temporal Variability Yolo Bypass: Sediment MeHg concentrations range 6-fold annually within a given rice field Seasonality Matters!! JULY JUNE (newly seeded) DECEMBER (post harvest) AUGUST

  15. Temporal Variability Yolo Bypass: Seasonally decoupled MeHg cycling Summer- High bioaccumulation, medium production, and low export Increase in 60 Days 12 X higher 6 X higher 3 X higher Ackerman and Eagles-Smith 2010, ES&T

  16. Temporal Variability Yolo Bypass: Plant bio-physics – E vs T • Evaporation concentrates constituents in place • Transpiration transports constituents into soil Summer Winter Bachand et al., in review, b • Export in Winter • Storage in Summer • Decouples periods of production and export Bachand et al. (a) 2013

  17. Yolo Bypass Wildlife Area: YWA Cosumnes River Preserve: CRP Spatial Variability (Rice) • Elemental Hg • THg = 50-400 ng/g • Silty soils, OM = 5 -10% • SO4 = 1 – 20 mg/L • Organic (white) rice • Cinnabar + elemental Hg • THg = 200-500 ng/g • Clayey soils, OM=2-10% • SO4 = 10 – 300 mg/L • Conventional (white) rice/ wild rice/ fallow rotation Twitchell Island: TR • Elemental Hg • THg = 50-150 ng/g • Organic soils, OM=10-40% • SO4 = 20 – 500 mg/L • Conventional (white) rice All rice fields flooded in summer AND winter (2 flood periods) Fleck (USGS) 2013

  18. Spatial Variability (Rice) Seasonal net MeHg export from rice fields Source Sink Fleck (in preparation)

  19. Spatial Variability (Rice) wild rice W32 W65 white rice R31 R64 fallow fields F20 F66 Seasonal Export not a function of MeHg production Marvin-DiPasquale et al., 2013, STOTEN

  20. We still have many science gaps to address for MeHg TMDL. To get from micro to macro, one must consider • Production (Hg, carbon, redox) • Transport (“plumbing”, degradation) • Bioaccumulation (season, sensitivity) Thank you. lwindham-myers@usgs.gov Yolo Bypass papers (n=8), in press, STOTEN special section (2013) www.kevinstewartfishing.com

  21. Key findings of synthesis(Windham-Myers and Ackerman, 2102) • Hydrologic Control • Slowing water flow increases rates of storage and degradation of MeHg more than production. • BUT • Slowing water concentrates surface water MeHg and enhances in situ bioaccumulation in fish. • Permanent Wetlands • Rates of MeHg storage and degradation may exceed processes of MeHg production (net sink). • BUT • High soil carbon (peat) may produce more MeHg than they remove (net source). • Seasonal Wetlands • Rewetting of dried wetlands regenerates biogeochemical species that enhance MeHg production. • reactive Hg • ferric iron (FeIII) • sulfate (SO4) • labile carbon • Flood-up of dried wetlands can generate an initial pulse of MeHg from sediment to surface waters. • TEMPORAL VARIABILITY in matrix concentrations can be orders of magnitude • “Hot moments” drive annual patterns of MeHg production and export in seasonal wetlands. • Diel patterns in surface water – lower concentrations during daylight, higher concentrations at night – may be important in shallow vegetated habitats, due to dominant effects of photodemethylation and/or downward advective storage of MeHg through transpiration.. • Biota MeHg concentrations vary over time, and breeding season is when wildlife is most vulnerable. • SPATIAL VARIABILITY can relate to different initial conditions or management practices. • Total Hg concentrations are often poorly correlated with MeHg concentrations. • Soil organic matter is associated with MeHg in wetlands and irrigated agriculture. • Wetlands can be a MeHg sink or source based on the relative loads of sourcewater and tailwater.

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