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Mercury & GCAP

Mercury & GCAP. Nicole Smith-Downey, Noelle Eckley Selin, Chris Holmes, Bess Sturges, Daniel Jacob Harvard University Elsie Sunderland US EPA Sarah Strode, Lyatt Jaegle University of Washington. Phytoplankton. Zooplankton. Planktivorous fish. Piscivorous fish. Bf ~ 10 4.

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Mercury & GCAP

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  1. Mercury & GCAP Nicole Smith-Downey, Noelle Eckley Selin, Chris Holmes, Bess Sturges, Daniel Jacob Harvard University Elsie Sunderland US EPA Sarah Strode, Lyatt Jaegle University of Washington

  2. Phytoplankton Zooplankton Planktivorous fish Piscivorous fish Bf ~ 104 Bf ~ 105 Bf ~ 106 Bf = 106–107 Why Hg? Biomagnification of MeHg in the food web impacts global human and animal health Reduction in intelligence, reduced reproductive success, brain, liver and kidney damage

  3. The Mercury Cycle ATMOSPHERE 5000 (3x pre-industrial) Anthropogenic Emissions 2400 Land emissions 1600 Wet & Dry Deposition 2600 Wet & Dry Deposition 1900 Oceanic Evasion 1500 (1680-3120) (700-3500) (1800-3600) (1300-2600) (700-3500) SURFACE SOILS 1,000,000 OCEAN 289,000 Extraction from deep reservoirs 2400 Rivers 200 (1680-3120) Quantities in Mg/year (106 g, or metric tonnes) Uncertainty ranges in parentheses Adapted from Mason & Sheu, 2002 Net burial 200

  4. Hg in GEOS-Chem (current simulation) • Coupled land-atmosphere-ocean (pre-industrial and present) • OH, O3 oxidation, reduction; sea-salt uptake of Hg(II) • Wet & dry deposition adjusted to match MDN observations • 2nd generation ‘under construction’ • Halogens as possible oxidant (Holmes) • New mechanistic terrestrial Hg model linking the lifetime of Hg in the environment to carbon pools (Smith-Downey) • New oceanic Hg model including deeper ocean layers (Sunderland)

  5. Emissions Scenarios IPCC Emissions Scenarios for SO2

  6. Atmospheric chemistry & dynamics Possible changes • Patterns in precipitation • Transport • Clouds (Hg(II) -> Hg0) • Wind speed & sea salt • T dependence of Rxns • Feedbacks from other changes in chemistry Wet deposition of Hg over US Selin

  7. Plan of Action • Changes in dynamics and their influence on Hg deposition can be analyzed by the current model • Changes in chemistry (OH, O3) may influence Hg, but uncertainties in those effects are large

  8. Ocean uptake and evasion Possible Changes • Hg solubility (T) • Wind speed • Mixed layer depth • NPP - (Hg(II) -> Hg0) - particulates • Memory of past emissions Strode 2006

  9. Plan of Action • Architecture of current model will lead to rapid equilibration with changes in T and deposition • Can be used to examine first order effects of T, wind speed and deposition • Deeper ocean model will greatly increase our ability to predict future ocean response to change • Sunderland

  10. Sea Ice - Halogens - and MDE’s Sea ice extent

  11. Plan of Action • Current standard model does not include halogens • Holmes • Possible effects are large, but uncertainties in the interaction between Br, sea-ice and Hg will limit our predictive capabilities

  12. Hg in the terrestrial biosphere oxidation Hg(II) Hg0 reduction litterfall throughfall (wet) Hg0 Hg(II) Binding to organic ligands Hg(II)aq

  13. Biomass Burning Gillet et al 2004 Turetsky et al 2006 • Changes in fire frequency and intensity expected • Net loss of stored Hg from soils - especially in Arctic • Weidenmeier et al. (in press) estimate domestic BB emissions are nearly equal to primary emissions from coal combustion

  14. Soil Respiration • Soil respiration is temperature and moisture dependent • Decomposition of organic soils will release stored Hg to the atmosphere • Kirshbaum 1995 suggests 10% C loss in areas with a MAT = 5C • Because the pool of soil Hg is large, even small changes in the lifetime will have a significant impact on land emissions

  15. Plan of Action • Architecture of current model will lead to rapid equilibration with changes in T and deposition • New land model will allow us to account for new emissions from respiration and biomass burning • Smith-Downey Predicted Biomass Burning Spracklen - Harvard

  16. Climate  Emissions ?  Chemistry

  17. Phytoplankton Zooplankton Planktivorous fish Piscivorous fish Bf ~ 104 Bf ~ 105 Bf ~ 106 Bf = 106–107 Why Hg? MeHg loading of birds and mammals has increased over time Hg in Polar Bear Hair Hg in Bird Feathers Dietz 2006 Thompson 1992

  18. Sea Ice - Halogens - and MDE’s Depends on addition of Halogen chemistry and some link to sea ice/snow

  19. The Mercury Land Model Hg(II) dry Hg(II) wet Hg0 dry atmosphere (2) (3) (1) Vegetation/ Soil surface (5) (6) (4) Hg(II) dry Hg0 dry Hg leaf (7) (8) (9) Soils Hg(II) org Hg(II) aq (11) (10)

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