sarah strode, lyatt jaeglé, dan jaffe, peter weiss-penzias, phil swartzendruber university of...
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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
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
Deposition to U.S.
Hg Emissions from Asia
SourcesMg/yr
Hg0 HgII HgP
Anthro 613 380 89
Natural 120 0 0
Reemis 373 0 0
BB 109 0 0
Land emission where geologic depositsLand reemissions follow deposition patternBiomass burning scaled to COEmissions+reemissions from slab ocean
Trans-Pacific Hg Transport
Hg0 & CO transported across PacificHgII at lower latitudes from Hg0 oxidation
March-May averages
Deposition largest over E. Asia & SW N. America
Asian anth CO at 700 hPa Asian anth Hg0 at 700 hPa
Asian anth HgII at 700 hPa Asian anth HgII deposition
Vertical View of Transport
March-May, 28°-60°N average
Asian Hg0 & CO trans-Pacific transport decreases w/ height
HgII transport in upper troposphere
Ocean reemission increases transport
Including ocean reemission of Asian Hg
Asia N. Am
Asian FF CO Asian anth Hg0 Asian anth HgII
Asian anth Hg0 Asian anth HgII
pres
sure
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
Hg0 obs and model
ALRTevent
Model
Asian anthro
Asian land
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
Hg
0 (n
g/m
3 )
ng/m3/ppb Hg/CO
All Okinawa
Event mean
Obs 0.0053 0.0056
Std 0.0041 0.0050
Obs from Jaffe et al. [2005]
reduction of HgII emission adds ~20% increasing anth + decreasing land overestimates Hg0 conc.
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]
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 cyclingMore sophisticated ocean formulationTrack Hg partitioning between soil, ocean, and atmospheric reservoirs thru time