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Approach Estimating Mercury Dry Deposition for AMNeT

Approach Estimating Mercury Dry Deposition for AMNeT. Leiming Zhang Air Quality Research Division Science and Technology Branch Environment Canada, Toronto. Gaseous oxidized Hg (GOM) Particulate-bound Hg (PBM ) Gaseous elemental Hg (GEM). Dry deposition model for GOM.

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Approach Estimating Mercury Dry Deposition for AMNeT

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  1. Approach Estimating Mercury Dry Deposition for AMNeT LeimingZhang Air Quality Research Division Science and Technology Branch Environment Canada, Toronto

  2. Gaseous oxidized Hg (GOM) Particulate-bound Hg (PBM) Gaseous elemental Hg (GEM)

  3. Dry deposition model for GOM A big-leaf gaseous dry deposition model Zhang et al., 2003 ACP Zhang et al., 2009 A.E

  4. Annual average Vd Zhang et al., 2012 ACP

  5. Dry deposition model for PBM A size-resolved dry deposition model Zhang et al., 2001 A.E

  6. Assumed size distribution PM2.5-10 PM10+ dM/d(logD)(frequency, %) PM2.5 Aerodynamic diameter D (m) Zhang et al., 2012 ACP

  7. Non-negligible coarse Hg mass fraction and higher Vd for coarse Fang et al., 2012 A.E.

  8. Coarse Hg contributed 50-85% of the total particulate Hg dry deposition Fang et al., 2012 A.E.

  9. Recommendation for PBM Vd for both fine and coarse PM will be provided CF – assumed mass fraction for coarse PBM

  10. Previous approach for GEM Same model as for GOM but with different input parameters and with annual natural emission from GRAHM Zhang et al., 2012 ACP

  11. Proposed new approach - Bi-directional exchange model

  12. Knowledge on GEM bi-directional exchange Sample vegetation measurements Data trends • Higher compensation points in light over dark conditions • Higher values in spring and summer • Increases with growth of foliage • More dependent on ambient atmospheric [Hg] than soil [Hg] Hansen et al., 1995; Ericksen and Gustin, 2004 12

  13. Knowledge on GEM bi-directional exchange Sample soil measurements Data trends • Higher compensation points in light conditions • Increases with increasing soil [Hg] • Strong dependence on solar radiation • Dependent on ambient and soil temperatures • Seasonal changes more noticeable over ground surfaces than vegetation Xin and Gustin, 2007; Gustin et al., 2006; Edwards and Howard, 2012 13 13

  14. Knowledge on GEM bi-directional exchange • Soil conditions • pH, moisture, [Hg], temperature all increase emissions • Canopy Growth Stage - Trend of deposition in spring - Increasing emissions in summer with foliage • Canopy wetness • Increase in emissions in dry conditions • Increase in deposition with canopy/leaf wetness • Atmospheric Hg0 Concentration • Higher [Hg0] → deposition, lower [Hg0] → emission • Diurnal variations • Emission in daytime/light conditions • Deposition in nighttime/dark conditions

  15. Knowledge on GEM bi-directional exchange • Soil conditions • pH, moisture, [Hg], temperature all increase emissions • Canopy Growth Stage - Trend of deposition in spring - Increasing emissions in summer with foliage • Canopy wetness • Increase in emissions in dry conditions • Increase in deposition with canopy/leaf wetness • Atmospheric Hg0 Concentration • Higher [Hg0] → deposition, lower [Hg0] → emission • Diurnal variations • Emission in daytime/light conditions • Deposition in nighttime/dark conditions

  16. Example model results 16

  17. Input data Meteorology data: Model output from Canadian weather forecast model at 15 km x 15 km resolution at surface and the first model layer Land use data: GIS generated 1 km or 2 km circle from remote sensing data, converted to 26 LUC used in the dry deposition models Brook et al., 1999 A.E. Zhang et al., 2012 ACP 17

  18. References • Brook J.R., Zhang L., Franco D., and Padro J., 1999. Description and evaluation of a model of deposition velocities for routine estimates of air pollutant dry deposition over North America. Part I. Model development. Atmospheric Environment, 33, 5037-5052. • Zhang L. Gong S., Padro J., and Barrie L.A., 2001. A size-segregated particle dry deposition scheme for an atmospheric aerosol module. Atmospheric Environment, 35, 549-560. • Zhang L., Brook J.R., and Vet R., 2003. A revised parameterization for gaseous dry deposition in air-quality models. Atmospheric Chemistry and Physics, 3, 2067-2082. • Zhang L., Wright L.P., and Blanchard P., 2009. A review of current knowledge concerning dry deposition of atmospheric mercury. Atmos. Environ 43, 5853-5864. • Zhang L., Blanchard P., Gay D.A., Prestbo E.M., Risch M.R., Johnson D., Narayan J., Zsolway R., Holsen T.M., Miller E.K., Castro M.S., Graydon J.A., St. Louis V.L., and Dalziel J., 2012. Estimation of speciated and total mercury dry deposition at monitoring locations in eastern and central North America. Atmos. Chem. Phys. 12, 4327-4340. • Fang G.C., Zhang L., and Huang C.S., 2012. Measurements of size-fractionated concentration and bulk dry deposition of atmospheric particulate bound mercury. Atmos. Environ. 61, 371-377. • Wright L.P., Zhang L., et al., 2013. Modeling bi-directional air-surface exchange for elemental gaseous mercury. In preparation.

  19. Acknowledgements • Pierrette Blanchard • Jeffrey R. Brook • SilvinaCarou • David Johnson • Julie Narayan • L. Paige Murphy • et al. • David Gay, AMNeT contributors, and many U.S. colleagues

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