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

Hg emissions & long-range transport Hg 0 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 Deposition to U.S.

Hg Emissions from Asia Sources Mg/yr Hg 0 Hg II Hg P Anthro Natural12000 Reemis37300 BB10900 Land emission where geologic deposits Land reemissions follow deposition pattern Biomass burning scaled to CO Emissions+reemissions from slab ocean

Trans-Pacific Hg Transport Hg 0 & CO transported across Pacific Hg II at lower latitudes from Hg 0 oxidation March-May averages Deposition largest over E. Asia & SW N. America Asian anth CO at 700 hPaAsian anth Hg 0 at 700 hPa Asian anth Hg II at 700 hPaAsian anth Hg II deposition

Vertical View of Transport March-May, 28°-60°N average Asian Hg 0 & CO trans-Pacific transport decreases w/ height Hg II transport in upper troposphere Ocean reemission increases transport Including ocean reemission of Asian Hg AsiaN. Am Asian FF COAsian anth Hg 0 Asian anth Hg II Asian anth Hg 0 Asian anth Hg II pressure

Timeseries at Okinawa, Spring 2004 Asian antrhopogenic tracer dominates variability Asian land Hg tracer covaries with Asian anthro tracer Obs from Jaffe et al. [2005] CO obs and model Hg 0 obs and model ALRT event Model Asian anthro Asian land

Constraining Asian Hg emissions Observed Hg 0 /CO enhancement ratio during Asian LRT events ~twice ratio expected for emissions [Jaffe et al., 2005]: Underestimate in anthropogenic Hg 0 emission Covariance w/ Asian land emission/reemission Production of Hg 0 during transport Can the model distinguish these possibilities? Slope=.0053,.0041,.0027 r 2 =.84,.82,.84 Hg 0 (ng/m 3 ) ng/m 3 /ppb Hg/CO All Okinawa Event mean Obs Std Obs from Jaffe et al. [2005]  reduction of Hg II emission adds ~20%  increasing anth + decreasing land overestimates Hg 0 conc.

Timeseries at Mount Bachelor, OR CO underestimate in spring Captures mean Hg but peaks underestimated N. American land emissions are major contributor Model statistics: CO: mean model/obs = 0.89, r 2 = 0.35 Hg 0 : mean model/obs = 1.02, r 2 = obs and model: CO 2004 obs and model: Hg 0 Peak at 2.8 km a.s.l. – upslope/downslope flow Less variability than Okinawa Obs from Weiss-Penzias et al. [2006] 2004 tracer contributions: Hg 0

RGM at MBO, April-Aug 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]

Conclusions & Future work Land emissions + reduction of Hg II can explain most of the observed Hg/CO ratio: anthropogenic inventory may be ok Asian Hg 0 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

22.4 Mmol Hg 0 Land Ocean mixed layer Atmosphere 1.0 Wet & dry deposition Ocean evasion Mmol Hg II Oxidation Mmol Hg P Land emissions Wet & dry deposition 1.0 Anthropogenic emissions Reduction Global GEOS-Chem Hg Budget Hg 0 oxidation to Hg II (RGM) by O 3 & OH; Hg II reduction in clouds Coupled to slab ocean model w/ sea-air exchange, chemistry and mixing w/ deep ocean Deep ocean Hg 0 Hg II Hg nr