Estimate of Mercury Emission from Natural Sources in East Asia Suraj K. Shetty 1 *, Che-Jen Lin 1, David G. Streets 2, Carey Jang 3, Thomas C. Ho 1 and Hsing-wei Chu 1, Taruna Vanjani 1 1 College of Engineering, Lamar University, Beaumont, TX 2 Decision and Information Sciences Division, Argonne National Laboratory, Argonne, IL 3 Office of Air Quality Planning and Standards, USEPA, Research Triangle Park, NC 2007 CMAS Conference Session 4: Emissions Inventories, Modeling and Analysis October 2, 2007, Chapel Hill, NC

Mercury Emissions Anthropogenic sources Coal-fired power plants, Coal-fired power plants, Mining and industrial metal processing Mining and industrial metal processing Chloro-alkali production, waste incineration Chloro-alkali production, waste incineration Natural sources / re-emission Volcanic eruptions, degassing, biomass burning Volcanic eruptions, degassing, biomass burning Emissions from vegetation, soil and water surfaces Emissions from vegetation, soil and water surfaces –caused by past mercury emission and deposition from both natural and anthropogenic sources –Photochemical reduction, biotic and abiotic processes

Issues of Mercury Emissions Anthropogenic Hg emission is speciated and well documented … Mg/yr [Pacyna et al., 2006] Anthropogenic Hg emission is speciated and well documented … Mg/yr [Pacyna et al., 2006] Natural Hg emission was either assumed to be balanced by GEM deposition, or a fraction (30- 50%) of modeled Hg deposition [Bullock & Bhreme, 2002; Seigneur et al., 2004, Lin et al., 2005] Natural Hg emission was either assumed to be balanced by GEM deposition, or a fraction (30- 50%) of modeled Hg deposition [Bullock & Bhreme, 2002; Seigneur et al., 2004, Lin et al., 2005] May dominate anthropogenic emission [Lindberg et al., 1998] May dominate anthropogenic emission [Lindberg et al., 1998] Mg/yr …Highly uncertain ! Mg/yr …Highly uncertain !

Natural Hg Emission Process Diurnal and seasonal variation observed for emission from vegetation, soil and water surfaces Diurnal and seasonal variation observed for emission from vegetation, soil and water surfaces Strongly affected by meteorological parameters (temperature, pressure, solar radiation, etc.) Strongly affected by meteorological parameters (temperature, pressure, solar radiation, etc.) Emission flux varies according to the land cover [Lindberg et al., 1998, 2002] Emission flux varies according to the land cover [Lindberg et al., 1998, 2002] GEM transpiration rate varies with species of vegetation [Obrist et al., 2004, Zhang et al., 2005] GEM transpiration rate varies with species of vegetation [Obrist et al., 2004, Zhang et al., 2005] Net flux depends on ambient Hg levels and soil Hg contents [Frescholtz et al., 2004] Net flux depends on ambient Hg levels and soil Hg contents [Frescholtz et al., 2004]

Why East Asia Domain ? Recent studies have focused on the North American region [Xu et al., 1999; Lin and Tao, 2003; Bash et al, 2004; Lin et al., 2005; Gbor et al., 2006] Recent studies have focused on the North American region [Xu et al., 1999; Lin and Tao, 2003; Bash et al, 2004; Lin et al., 2005; Gbor et al., 2006] Asia amounts to about 54% of the global anthropogenic Hg emissions with China contributing to 50% of the Asian Emission [Seigneur et al., 2004; Pacyna et al., 2006; Streets et al., 2005] Asia amounts to about 54% of the global anthropogenic Hg emissions with China contributing to 50% of the Asian Emission [Seigneur et al., 2004; Pacyna et al., 2006; Streets et al., 2005] With natural emission, total Hg emission from East Asia would be quite a considerable amount With natural emission, total Hg emission from East Asia would be quite a considerable amount Model uncertainties and under-predictions Model uncertainties and under-predictions

Estimating Hg Emission from Natural Processes Emission from Vegetation Emission from Vegetation Emission from Soil Emission from Soil Emission from Soil under the Canopy Emission from Soil under the Canopy Emission from Water Emission from Water

Emission from Vegetation F e - Hg emission flux E t - Evapotranspiration rate C s - Hg soil water concentration [ Monteith and Unsworth, 1990 ] [ Xu et al., 1999 ] Rn - the net radiation G - soil heat flux (e s - e a ) - vapor pressure deficit of the air  a - mean air density at constant pressure C p - specific heat of the air  - slope of sat. vapor press.- temp. curve  - psychrometric constant r s - bulk surface resistance r a - aerodynamic resistance [ Monteith and Unsworth, 1990 ] r l - bulk stomatal resistance LAI - Leaf Area Index

Emission from Soil 1. [ Gbor et al., 2006 ] F s - Hg soil emission flux Hg s - soil mercury concentration T s - soil temperature n, , m - constants 2a. [ Gbor et al., 2006 ] 2b. [ Monteith, 1973 ] F sc – Hg soil flux under canopy R g - solar radiation reaching ground R gc - solar radiation under canopy Hg s - soil mercury concentration LAI – leaf area index - extinction coefficient - extinction coefficient a, b, c - constants

Emission from Water [ Bash et al., 2004 ] F w - Hg water emission flux k l - mass transfer coefficient C w - Hg concentration in water C a - Hg concentration in air H – Henry’s law constant U – wind speed at 10 m Sc hg - schmidt number for Hg Sc co2 - schmidt number for CO 2 [ Wanninkhof et al., 1992 ] Henry’s law constant = ƒ (temperature) [ Sanemasa, 1975 ] Sc = ƒ (temperature) … approach followed by Lin and Tao, 2003 C w = 0.04 ng/l [ Xu et al., 1999 ]

Domain Specifications 36-km spatial resolution, 164 x 97, 1 layer domain grid 36-km spatial resolution, 164 x 97, 1 layer domain grid Lambert Conformal projection centered at 34 N, 110 E Lambert Conformal projection centered at 34 N, 110 E East Asia domain covers about 70 % of Asia (includes entire China region and some parts of it neighboring countries) East Asia domain covers about 70 % of Asia (includes entire China region and some parts of it neighboring countries) 2001 meteorology data from USEPA’s ICAP program 2001 meteorology data from USEPA’s ICAP program

Simulation Approach Model MCIP Landuse Data LAI Data Vegetation Soil under Canopy Soil Water Gridded Emission Flux Natural Hg Emission Model Hg Soil Conc. Data Hg Air Conc. Data* * Lin et al, 2006b

Hg Soil Concentration (China) Background concentration of Hg in soils of China (from Chinese Environmental monitoring center, 1992)

Landuse data Study Domain Landuse from Global Landuse Data

LAI Data (a)(b) The 8-day average Leaf Area Index (LAI) data was obtained from MODIS satellite products: (ftp://primavera.bu.edu/pub/datasets/MODIS). The downloaded binary formats were converted into the model ready format using ENVI® (Environment for Visualizing Images), an image processing software. (a) January (b) Julyftp://primavera.bu.edu/pub/datasets/MODIS

Simulation and Calculations Simulations were performed for the month of January, April, July and October 2001 Simulations were performed for the month of January, April, July and October 2001 Months are representative of the seasonal meteorological variation in the domain Months are representative of the seasonal meteorological variation in the domain Calculated hourly emission fluxes were summed for the entire month in each grid to show the spatial distribution of the natural emission Calculated hourly emission fluxes were summed for the entire month in each grid to show the spatial distribution of the natural emission Annual emissions were estimated as three times of the four-month’s sum Annual emissions were estimated as three times of the four-month’s sum

Diurnal Variation JanuaryApril JulyOctober

Diurnal Variation

Seasonal Variation JanuaryApril JulyOctober

Comparison of Estimates

Results & Conclusions Estimated Hg flux ranges from ng m -2 hr -1 from vegetation, the flux from soil (<12 ng m -2 hr -1 ) and water (<5 ng m -2 hr -1 ) is much smaller Estimated Hg flux ranges from ng m -2 hr -1 from vegetation, the flux from soil (<12 ng m -2 hr -1 ) and water (<5 ng m -2 hr -1 ) is much smaller Total emission from domain is 830 Mg yr -1, the emission from China is about 460 Mg yr -1 Total emission from domain is 830 Mg yr -1, the emission from China is about 460 Mg yr -1 Natural Hg emission accounted to about 50-55% of the total Hg emissions for the year 2001 Natural Hg emission accounted to about 50-55% of the total Hg emissions for the year 2001 Emission exhibits diurnal variation and strongly depends on temperature, radiation, vegetation coverage and mercury concentrations in soils Emission exhibits diurnal variation and strongly depends on temperature, radiation, vegetation coverage and mercury concentrations in soils Higher emission occur in the south due to denser vegetation coverage and higher Hg soil concentrations Higher emission occur in the south due to denser vegetation coverage and higher Hg soil concentrations Natural Hg emission can dominate anthropogenic source in summer Natural Hg emission can dominate anthropogenic source in summer

Acknowledgements Texas Commission on Environmental Quality (TCEQ Work Order Number: ) Texas Commission on Environmental Quality (TCEQ Work Order Number: ) The USEPA Office of Air Quality Planning & Standards (RTI Subcontract Number: ) The USEPA Office of Air Quality Planning & Standards (RTI Subcontract Number: ) Texas Air Research Center (TARC Project Number: 077LUB0976) Texas Air Research Center (TARC Project Number: 077LUB0976)