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Trans-Pacific Transport of Mercury

Trans-Pacific Transport of Mercury. Sarah Strode, Lyatt Jaeglé, Dan Jaffe, Peter Weiss-Penzias, Phil Swartzendruber University of Washington Noelle Eckley Selin, Chris Holmes, Daniel Jacob Harvard. Can GEOS-Chem capture observed Hg lrt events?

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Trans-Pacific Transport of Mercury

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  1. Trans-Pacific Transport of Mercury Sarah Strode,Lyatt Jaeglé, Dan Jaffe, Peter Weiss-Penzias, Phil Swartzendruber University of Washington Noelle Eckley Selin, Chris Holmes, Daniel Jacob Harvard • Can GEOS-Chem capture observed Hg lrt events? • What can observed Hg/CO ratios tell us about Asian Hg emissions?

  2. Hg emissions & long-range transport Deposition to U.S. • Hg0 lifetime ~1 year  global transport • Approx. 1/3 of emissions anthropogenic: ~50% from Asia  underestimated? • Long-range transport important for North American concentrations Pacyna et al., 2005 Seigneur et al., 2004

  3. Hg Emissions from Asia • Land emission where geologic deposits • Land reemissions follow deposition pattern • Biomass burning scaled to CO • Emissions+reemissions from slab ocean

  4. Trans-Pacific Hg Transport Asian anth CO at 700 hPa Asian anth Hg0 at 700 hPa March-May averages • Hg0 & CO transported across Pacific • HgII at lower latitudes from Hg0 oxidation Asian anth HgII at 700 hPa Asian anth HgII deposition • Deposition largest over E. Asia & SW N. America

  5. Vertical View of Transport Asian FF CO Asian anth Hg0 Asian anth HgII pressure • March-May, 28°-60°N average • Asian Hg0 & CO trans-Pacific transport decreases w/ height • HgII transport in upper troposphere • Ocean reemission increases transport Asia N. Am Including ocean reemission of Asian Hg Asian anth Hg0 Asian anth HgII

  6. Timeseries at Okinawa, Spring 2004 Obs from Jaffe et al. [2005] CO obs and model • Asian antrhopogenic tracer dominates variability • Asian land Hg tracer covaries with Asian anthro tracer ALRT event Hg0 obs and model Model Asian anthro Asian land

  7. Constraining Asian Hg emissions • Observed Hg0/CO enhancement ratio during Asian LRT events ~twice ratio expected for emissions [Jaffe et al., 2005]: • Underestimate in anthropogenic Hg0 emission • Covariance w/ Asian land emission/reemission • Production of Hg0 during transport • Can the model distinguish these possibilities? Slope= .0053, .0041, .0027 r2 = .84, .82, .84 Hg0 (ng/m3) • reduction of HgII emission adds ~20% • increasing anth + decreasing land overestimates Hg0 conc. Obs from Jaffe et al. [2005]

  8. RGM at MBO, April-Aug. 2005 • Model captures timing of some events but underestimates magnitude • Greater subsidence could give higher RGM • Oxidation of global pool, not direct transport Obs from Swartzendruber et al. [2006]

  9. Conclusions & Future work • Land emissions + reduction of HgII can explain most of the observed Hg/CO ratio: anthropogenic inventory may be ok • Asian Hg0 reaches N. America by direct transport, while RGM descends from the high altitude global pool Future plans: biogeochemical Hg cycling • More sophisticated ocean formulation • Track Hg partitioning between soil, ocean, and atmospheric reservoirs thru time

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