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.

Estimate of Mercury Emission from Estimate of Mercury Emission from Natural Sources in East AsiaNatural Sources in East Asia

Suraj K. ShettySuraj K. Shetty11*, Che-Jen Lin*, Che-Jen Lin11, David G. Streets, David G. Streets22, , Carey JangCarey Jang33, Thomas C. Ho, Thomas C. Ho1 1 and Hsing-wei Chuand Hsing-wei Chu1 1 , Taruna Vanjani, Taruna Vanjani11

11College of Engineering, Lamar University, Beaumont, TX College of Engineering, Lamar University, Beaumont, TX 22Decision and Information Sciences Division, Argonne National Laboratory, Argonne, IL Decision and Information Sciences Division, Argonne National Laboratory, Argonne, IL

33Office of Air Quality Planning and Standards, USEPA, Research Triangle Park, NCOffice of Air Quality Planning and Standards, USEPA, Research Triangle Park, NC

2007 CMAS Conference 2007 CMAS Conference Session 4: Emissions Inventories, Modeling and AnalysisSession 4: Emissions Inventories, Modeling and Analysis

October 2, 2007, Chapel Hill, NCOctober 2, 2007, Chapel Hill, NC

Mercury EmissionsMercury Emissions

Anthropogenic sourcesAnthropogenic sources Coal-fired power plants, Coal-fired power plants, Mining and industrial metal processingMining and industrial metal processing Chloro-alkali production, wChloro-alkali production, waste incinerationaste incineration

Natural sources / re-emissionNatural sources / re-emission Volcanic eruptions, degassing, biomass burningVolcanic eruptions, degassing, biomass burning Emissions from vegetation, soil and water surfacesEmissions from vegetation, soil and water surfaces

– caused by past mercury emission and deposition caused by past mercury emission and deposition from both natural and anthropogenic sourcesfrom both natural and anthropogenic sources

– Photochemical reduction, biotic and abiotic Photochemical reduction, biotic and abiotic processes processes

Issues of Mercury Emissions Issues of Mercury Emissions

Anthropogenic Hg emission is speciated and Anthropogenic Hg emission is speciated and well documented …. 2200 Mg/yr [well documented …. 2200 Mg/yr [Pacyna et Pacyna et al.al., 2006], 2006]

Natural Hg emission was either assumed to be Natural Hg emission was either assumed to be balanced by GEM deposition, or a fraction (30-balanced by GEM deposition, or a fraction (30-50%) of modeled Hg deposition [50%) of modeled Hg deposition [Bullock & Bullock & Bhreme, 2002Bhreme, 2002; ; Seigneur et al., 2004, Lin et al., Seigneur et al., 2004, Lin et al., 20052005] ]

May dominate anthropogenic emission May dominate anthropogenic emission [[Lindberg et al., 1998Lindberg et al., 1998]]

1000-4200 Mg/yr …Highly uncertain !1000-4200 Mg/yr …Highly uncertain !

Natural Hg Emission ProcessNatural Hg Emission Process

Diurnal and seasonal variation observed for emission Diurnal and seasonal variation observed for emission from vegetation, soil and water surfacesfrom vegetation, soil and water surfaces

Strongly affected by meteorological parameters Strongly affected by meteorological parameters (temperature, pressure, solar radiation, etc.) (temperature, pressure, solar radiation, etc.)

Emission flux varies according to the land cover Emission flux varies according to the land cover [[Lindberg et al., 1998, 2002Lindberg et al., 1998, 2002]]

GEM transpiration rate varies with species of GEM transpiration rate varies with species of vegetation [vegetation [Obrist et al., 2004, Zhang et al., 2005Obrist et al., 2004, Zhang et al., 2005]]

Net flux depends on ambient Hg levels and soil Hg Net flux depends on ambient Hg levels and soil Hg contents [contents [Frescholtz et al., 2004Frescholtz et al., 2004]]

WhyWhy East Asia Domain ?East Asia Domain ?

Recent studies have focused on the North American Recent studies have focused on the North American region [region [Xu et al., 1999; Lin and Tao, 2003; Bash et al, Xu et al., 1999; Lin and Tao, 2003; Bash et al, 2004; Lin et al., 2005; Gbor et al., 20062004; Lin et al., 2005; Gbor et al., 2006] ]

Asia amounts to about 54% of the global anthropogenic Asia amounts to about 54% of the global anthropogenic Hg emissions with China contributing to 50% of the Hg emissions with China contributing to 50% of the Asian Emission [Asian Emission [Seigneur et al., 2004; Pacyna et al., Seigneur et al., 2004; Pacyna et al., 2006; Streets et al., 20052006; Streets et al., 2005]]

With natural emission, total Hg emission from East Asia With natural emission, total Hg emission from East Asia would be quite a considerable amount would be quite a considerable amount

Model uncertainties and under-predictions Model uncertainties and under-predictions

Estimating Hg Emission from Estimating Hg Emission from Natural ProcessesNatural Processes

Emission from VegetationEmission from Vegetation Emission from SoilEmission from Soil Emission from Soil under the CanopyEmission from Soil under the Canopy Emission from Water Emission from Water

Emission from VegetationEmission from Vegetation

FFee - Hg emission flux - Hg emission flux EEtt - Evapotranspiration rate - Evapotranspiration rateCCss - Hg soil water concentration - Hg soil water concentration

ste CEF

a

s

a

aspan

t

rr

ree

CGR

E

1

)()(

[ Monteith and Unsworth, 1990 ]

[[ Xu et al., 1999 Xu et al., 1999 ]]

Rn - the net radiationG - soil heat flux(es - ea) - vapor pressure deficit of the aira - mean air density at constant pressure Cp - specific heat of the air - slope of sat. vapor press.- temp. curve - psychrometric constantrs - bulk surface resistancera - aerodynamic resistance

1. 2.

3. LAIrr ls /

[ Monteith and Unsworth, 1990 ]

rrll - bulk stomatal resistance - bulk stomatal resistance LAI - Leaf Area IndexLAI - Leaf Area Index

Emission from SoilEmission from Soil

mT

HgnFs

ss

lnln1.

[ [ Gbor et al., 2006Gbor et al., 2006 ] ]

FFss - Hg soil emission flux - Hg soil emission flux HgHgss - soil mercury concentration - soil mercury concentration TTss - soil temperature - soil temperaturen, n, , m - constants, m - constants

caRHgbF gcssc lnln2a.

[ [ Gbor et al., 2006Gbor et al., 2006 ] ]

LAIggc eRR 2b.

[ [ Monteith, 1973Monteith, 1973 ] ]

FFscsc – Hg soil flux under canopy – Hg soil flux under canopyRRgg - solar radiation reaching ground - solar radiation reaching groundRRgcgc - solar radiation under canopy - solar radiation under canopy HgHgss - soil mercury concentration - soil mercury concentration LAI – leaf area indexLAI – leaf area index - extinction coefficient- extinction coefficienta, b, c - constantsa, b, c - constants

Emission from WaterEmission from Water

H

CCkF awlw

[ [ Bash et al., 2004Bash et al., 2004 ] ]

FFww - Hg water emission flux - Hg water emission flux kkll - mass transfer coefficient - mass transfer coefficient CCww - Hg concentration in water - Hg concentration in waterCCaa - Hg concentration in air - Hg concentration in air H – Henry’s law constantH – Henry’s law constant

1.

2/1

2

6.145.0

co

hgl Sc

ScUk

2. U – wind speed at 10 m U – wind speed at 10 m ScSchghg - schmidt number for Hg - schmidt number for Hg ScScco2co2 - schmidt number for CO - schmidt number for CO22

[ [ Wanninkhof et al., 1992Wanninkhof et al., 1992 ] ]

Henry’s law constant = Henry’s law constant = ƒ (temperature)ƒ (temperature) [ [ Sanemasa, 1975Sanemasa, 1975 ] ]

Sc = Sc = ƒ (temperature)ƒ (temperature) … approach followed by … approach followed by Lin and Tao, 2003Lin and Tao, 2003

CCww = 0.04 ng/l [ = 0.04 ng/l [ Xu et al., 1999Xu et al., 1999 ] ]

Domain SpecificationsDomain Specifications

36-km spatial resolution, 36-km spatial resolution, 164 x 97, 1 layer domain 164 x 97, 1 layer domain gridgrid

Lambert Conformal Lambert Conformal projection centered at projection centered at 34 N, 110 E34 N, 110 E

East Asia domain covers East Asia domain covers about 70 % of Asia about 70 % of Asia (includes entire China (includes entire China region and some parts of region and some parts of it neighboring countries)it neighboring countries)

2001 meteorology data from USEPA’s ICAP program 2001 meteorology data from USEPA’s ICAP program

11

1

164

97

Simulation ApproachSimulation Approach

Model MCIP

LanduseData

LAI Data

Vegetation

Soil under Canopy

Soil

Water

GriddedEmission

Flux

Natural Hg EmissionModel

Hg SoilConc. Data

Hg Air Conc. Data*

* Lin et al, 2006b

Hg Soil Concentration (China)Hg Soil Concentration (China)

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

Landuse dataLanduse data

Study Domain Landuse from Global Landuse Data

LAI DataLAI 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) July

Simulation and CalculationsSimulation and Calculations

Simulations were performed for the month of Simulations were performed for the month of January, April, July and October 2001 January, April, July and October 2001

Months are representative of the seasonal Months are representative of the seasonal meteorological variation in the domainmeteorological variation in the domain

Calculated hourly emission fluxes were summed for Calculated hourly emission fluxes were summed for

the entire month in each grid to show the spatial the entire month in each grid to show the spatial distribution of the natural emissiondistribution of the natural emission

Annual emissions were estimated as three times of Annual emissions were estimated as three times of the four-month’s sum the four-month’s sum

Diurnal VariationDiurnal VariationJanuary April

July October

Diurnal VariationDiurnal Variation

0

5

10

15

20

25

8:00 AM 12:00 AM 4:00 PM 8:00 PM 12:00 PM 4:00 AMTime Steps (hr)

Avg

. Em

issi

on

(n

g/m

2-h

r)

January

April

July

October

Seasonal VariationSeasonal VariationJanuary April

July October

Comparison of EstimatesComparison of EstimatesTable 1. Estimated monthly natural emission from vegetation, soil and water (Mg)

Vegetation Soil (1) Water Total Emission from Total Emission from East Asia China region

January 13 6 11 30 8 April 46 7 8 61 29 July 108 9 9 126 88 October 42 7 12 61 29

Total Annual Emission 834 462

(1) Includes emission from soil and emission from soil under canopy

0

250

500

750

1000

East Asia China

Em

issi

ons

(Mg/

yr)

Natural Anthropogenic

0

10

2030

4050

6070

80

90

100

January April July October

Hg

Em

iss

ion

(M

g)

Natural Anthropogenic

Results & ConclusionsResults & Conclusions

Estimated Hg flux ranges from 0 - 66 ng mEstimated Hg flux ranges from 0 - 66 ng m-2 -2 hrhr-1 -1 from from vegetation, the flux from soil (<12 ng mvegetation, the flux from soil (<12 ng m-2 -2 hrhr-1-1) and ) and water (<5 ng mwater (<5 ng m-2 -2 hrhr-1-1) is much smaller ) is much smaller

Total emission from domain is 830 Mg yrTotal emission from domain is 830 Mg yr-1-1, the , the emission from China is about 460 Mg yremission from China is about 460 Mg yr-1-1

Natural Hg emission accounted to about 50-55% of Natural Hg emission accounted to about 50-55% of the total Hg emissions for the year 2001the total Hg emissions for the year 2001

Emission exhibits diurnal variation and strongly Emission exhibits diurnal variation and strongly depends on temperature, radiation, vegetation depends on temperature, radiation, vegetation coverage and mercury concentrations in soilscoverage and mercury concentrations in soils

Higher emission occur in the south due to denser Higher emission occur in the south due to denser vegetation coverage and higher Hg soil concentrationsvegetation coverage and higher Hg soil concentrations

Natural Hg emission can dominate anthropogenic Natural Hg emission can dominate anthropogenic source in summersource in summer

AcknowledgementsAcknowledgements

Texas Commission on Environmental Quality Texas Commission on Environmental Quality ((TCEQ Work Order Number: 64582-06-15TCEQ Work Order Number: 64582-06-15))

The USEPA Office of Air Quality Planning & The USEPA Office of Air Quality Planning & Standards (Standards (RTI Subcontract Number: 6-321-RTI Subcontract Number: 6-321-02102880210288))

Texas Air Research Center (Texas Air Research Center (TARC Project Number: TARC Project Number:

077LUB0976077LUB0976))