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

Why Hg? PhytoplanktonZooplanktonPlanktivorous fishPiscivorous fish Bf ~ 10 4 Bf ~ 10 5 Bf ~ 10 6 Bf = 10 6 –10 7 Reduction in intelligence, reduced reproductive success, brain, liver and kidney damage Biomagnification of MeHg in the food web impacts global human and animal health

Wet & Dry Deposition 2600 ATMOSPHERE 5000 (3x pre-industrial) SURFACE SOILS 1,000,000 OCEAN 289,000 Wet & Dry Deposition 1900 Oceanic Evasion 1500 Net burial 200 Land emissions 1600 Quantities in Mg/year (10 6 g, or metric tonnes) Uncertainty ranges in parentheses Adapted from Mason & Sheu, 2002 Anthropogenic Emissions 2400 Extraction from deep reservoirs 2400 Rivers 200 ( ) ( ) ( ) ( ) ( ) The Mercury Cycle

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)

IPCC Emissions Scenarios for SO 2 Emissions Scenarios

Atmospheric chemistry & dynamics Wet deposition of Hg over US Selin Possible changes Patterns in precipitation Transport Clouds (Hg(II) -> Hg 0 ) Wind speed & sea salt T dependence of Rxns Feedbacks from other changes in chemistry

Plan of Action Changes in dynamics and their influence on Hg deposition can be analyzed by the current model Changes in chemistry (OH, O 3 ) may influence Hg, but uncertainties in those effects are large

Ocean uptake and evasion Strode 2006 Possible Changes Hg solubility (T) Wind speed Mixed layer depth NPP - (Hg(II) -> Hg 0 ) - particulates Memory of past emissions

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

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

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

Hg in the terrestrial biosphere Hg 0 Hg(II) oxidation reduction Binding to organic ligands litterfall throughfall (wet) Hg 0 Hg(II) Hg(II) aq

Biomass Burning 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 Turetsky et al 2006Gillet et al 2004

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

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 Spracklen - Harvard Predicted Biomass Burning

 Emissions  Climate  Chemistry ?

Why Hg? PhytoplanktonZooplanktonPlanktivorous fishPiscivorous fish Bf ~ 10 4 Bf ~ 10 5 Bf ~ 10 6 Bf = 10 6 –10 7 MeHg loading of birds and mammals has increased over time Hg in Polar Bear Hair Hg in Bird Feathers Dietz 2006Thompson 1992

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

The Mercury Land Model Hg(II) dry Hg 0 dry atmosphere Vegetation/ Soil surface Soils Hg(II) wet Hg(II) dry Hg 0 dry Hg(II) org Hg(II) aq Hg leaf (1) (2)(3) (4) (5)(6) (8) (9) (10) (11) (7)