Modeling the Fate and Transport of Atmospheric Mercury in ... · Atmospheric Fate Processes for Hg...
Transcript of Modeling the Fate and Transport of Atmospheric Mercury in ... · Atmospheric Fate Processes for Hg...
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Modeling the Fate and Transportof Atmospheric Mercury inthe Chesapeake Bay Region
Dr. Mark CohenNOAA Air Resources Laboratory
Silver Spring, Maryland
Presentation atNOAA Chesapeake Bay OfficeMay 17, 2004, Annapolis MD
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• Modeling Methodology
• Hg Emissions Inventory
• Model Evaluation
• Some Results for Chesapeake Bay
• Some Next Steps
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Modeling Methodology
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Three “forms” of atmospheric mercuryElemental Mercury: Hg(0)
• ~ 95% of total Hg in atmosphere• not very water soluble• long atmospheric lifetime (~ 0.5 - 1 yr); globally distributed
Reactive Gaseous Mercury (“RGM”)• a few percent of total Hg in atmosphere• oxidized mercury: Hg(II)• HgCl2, others species?• somewhat operationally defined by measurement method• very water soluble• short atmospheric lifetime (~ 1 week or less);• more local and regional effects
Particulate Mercury (Hg(p)• a few percent of total Hg in atmosphere• not pure particles of mercury…
(Hg compounds associated with atmospheric particulate)• species largely unknown (in some cases, may be HgO?)• moderate atmospheric lifetime (perhaps 1~ 2 weeks)• local and regional effects• bioavailability?
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CLOUD DROPLET
cloud
PrimaryAnthropogenicEmissions
Elemental Mercury: Hg(0)Reactive Gaseous Mercury: RGMParticulate Mercury: Hg(p)
Atmospheric Fate Processes for Hg
Dry and Wet Deposition
Hg(0) oxidized to dissolvedRGM by O3, HOCl, OCl-
Hg(II) reduced to Hg(0) by SO2
Re-emission of natural AND previously depositedanthropogenic mercury
Adsorption/desorptionof Hg(II) to/from soot
Halogen-mediated oxidationon the surface of ice crystals
Hg(p)
“DRY” (low RH)ATMOSPHERE:
Hg(0) oxidized to RGMby O3, H202, Cl2, OH, HCl
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GAS PHASE REACTIONS
AQUEOUS PHASE REACTIONS
ReferenceUnitsRateReaction
Xiao et al. (1994); Bullock and Brehme (2002)
(sec)-1 (maximum)6.0E-7Hg+2 + h<→ Hg0
eqlbrm: Seigneur et al. (1998)
rate: Bullock & Brehme (2002).
liters/gram;t = 1/hour
9.0E+2Hg(II) ↔ Hg(II) (soot)
Lin and Pehkonen(1998)(molar-sec)-12.0E+6Hg0 + OCl-1 → Hg+2
Lin and Pehkonen(1998)(molar-sec)-12.1E+6Hg0 + HOCl → Hg+2
Gardfeldt & Jonnson (2003)(molar-sec)-1~ 0Hg(II) + HO2C→ Hg0
Van Loon et al. (2002)T*e((31.971*T)-12595.0)/T) sec-1
[T = temperature (K)]HgSO3 → Hg0
Lin and Pehkonen(1997)(molar-sec)-12.0E+9Hg0 + OHC→ Hg+2
Munthe (1992)(molar-sec)-14.7E+7Hg0 + O3 → Hg+2
Sommar et al. (2001)cm3/molec-sec8.7E-14Hg0 +OHC→ Hg(p)
Calhoun and Prestbo (2001)cm3/molec-sec4.0E-18Hg0 + Cl2 → HgCl2
Tokos et al. (1998) (upper limit based on experiments)
cm3/molec-sec8.5E-19Hg0 + H2O2 → Hg(p)
Hall and Bloom (1993)cm3/molec-sec1.0E-19Hg0 + HCl → HgCl2
Hall (1995)cm3/molec-sec3.0E-20Hg0 + O3 → Hg(p)
Atmospheric Chemical Reaction Scheme for Mercury
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Spatial interpolation
RECEPTOR
Impacts fromSources 1-3are ExplicitlyModeled
2
1
3
Impact of source 4 estimated fromweighted average of impacts of nearbyexplicitly modeled sources
4
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Transfer Coefficients
• refer to hypothetical emissions;[are independent of actual emissions]
• can be formulated with different units[in this example: total Hg deposition flux (ug/km2-yr) / emissions (g/yr)]
• will depend on the pollutant [in this example: Hg(0)]
• will depend on the receptor[in this example: Lake Superior]
• and the time period being modeled • [in this example: entire year 1996]
at any given location,the transfer coefficientis defined as the amountthat would be depositedin the given receptor(in this case, Lake Superior)if there were emissionsat that location.
Receptor =Lake Superior
Std Source Locations used for Interpolation
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MercuryEmissionsInventory
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Estimated 1999 U.S. Atmospheric Anthropogenic Mercury Emissions
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Estimated Speciation Profile for 1999 U.S.Atmospheric Anthropogenic Mercury Emissions
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Estimated 2000 Canadian AtmosphericAnthropogenic Mercury Emissions
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Geographic Distribution of Estimated Anthropogenic Mercury Emissions in the U.S. (1999) and Canada (2000)
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1990
(a)
1995
(b)
1995
/96/
99(c
)
1996
/99
(d)
1999
(e)
0
50
100
150
200
tons
/yea
r
pulp/paper productioncement manufacturinghazardous waste incinchlorine productionmunicipal waste incin.medical waste incin.coal-fired utility boilers
Reported trends in U.S. atmospheric mercuryemissions 1990-1999 (selected source categories)
(a) EPA NTI Baseline (Mobley, 2003)(b) Hg Study Rpt to Congress (EPA, 1997)(c) Inventory used in Cohen et al (2004)(d) EPA 96/99 Inventory (Ryan, 2001)(e) EPA NEI 1999 (draft) (Mobley, 2003)
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1995 Global Hg Emissions Inventory Josef Pacyna,NILU, Norway (2001)
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ModelEvaluation
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Mercury Deposition Network Sites with 1996 data in the Chesapeake Bay Region
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Jan-96Feb-96
Mar-96Apr-96
May-96Jun-96
Jul-96Aug-96
Sep-96Oct-96
Nov-96Dec-96
0.01
0.1
1
10
100
cum
ulat
ive
depo
sitio
n (u
g H
g/m
2)
measuredmodeled
Cumulative Wet Deposition at MDN_DE_02
Modeled vs. Measured Wet Deposition at Mercury Deposition Network Site DE_02 during 1996
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Jan-96Feb-96
Mar-96Apr-96
May-96Jun-96
Jul-96Aug-96
Sep-96Oct-96
Nov-96Dec-96
0.01
0.1
1
10
100
cum
ulat
ive
depo
sitio
n (u
g H
g/m
2)
measuredmodeled
Cumulative Wet Deposition at MDN_MD_13
Modeled vs. Measured Wet Deposition at Mercury Deposition Network Site MD_13 during 1996
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1999 Results forChesapeake Bay
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Geographical Distributionof 1999 Direct Deposition
Contributions to the Chesapeake Bay (entire domain)
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Geographical Distribution of 1999 Direct Deposition Contributions to the Chesapeake Bay (regional close-up)
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Geographical Distribution of 1999 Direct Deposition Contributions to
the Chesapeake Bay (local close-up)
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Emissions and Direct Deposition Contributions from Different Distance Ranges Away From the Chesapeake Bay
0 - 100100 - 200
200 - 400400 - 700
700 - 10001000 - 1500
1500 - 20002000 - 2500
> 2500
Distance Range from Chesapeake Bay (km)
0
20
40
60
80
Emis
sion
s (m
etric
tons
/yea
r)
0
2
4
6
8
Dep
ositi
on F
lux
(ug/
m2-
year
)
EmissionsDeposition Flux
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Largest Regional Individual Sources Contributing to1999 Mercury Deposition Directly to the Chesapeake Bay
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Largest Local Individual Sources Contributing to1999 Mercury Deposition Directly to the Chesapeake Bay
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Top 25 Contributors to 1999 Hg Deposition Directly to the Chesapeake Bay
Phoenix ServicesBrandon Shores
Stericycle Inc. Morgantown
Chalk PointNASA Incinerator
H.A. WagnerNorfolk Navy Yard
Hampton/NASA Incin.Chesapeake Energy Ctr.Chesterfield Yorktown
INDIAN RIVER Roxboro
BALTIMORE RESCO Mt. Storm Homer City Keystone BMWNC
Possum Point Montour
Phoenix ServicesBelews CreekHarrisburg Incin.Harford Co. Incin.
MD MD
MD MD
MD VA MD VA VA VA VA VA DE NC MD WV PA PA NC VA PA MD NC PA MD
0% 20% 40% 60% 80% 100%Cumulative Fraction of Hg Deposition
0
5
10
15
20
25R
ank
coal-fired elec genother fuel combustionwaste incinerationmetallurgicalmanufacturing/other
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municipal waste incin
medical waste incin
haz waste incin
other waste incin
metallurgical
cement/concrete
chloralkali
chemical manufacturing
other manufacturing
mobile sources
coal-fired elec gen
oil combustion (non-mobile)
all other fuel combustion
0.1 1 10 100 1000Atmospheric Mercury Deposition (kg Hg/yr)
to Bay surface to Watershed
Deposition to the Chesapeake Bay and to its Watershed (~1999)(logarithmic graph)
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municipal waste incin
medical waste incin
haz waste incin
other waste incin
metallurgical
cement/concrete
chloralkali
chemical manufacturing
other manufacturing
mobile sources
coal-fired elec gen
oil combustion (non-mobile)
all other fuel combustion
0 100 200 300 400 500 600 700Atmospheric Mercury Deposition (kg Hg/yr)
to Bay surface to Watershed
Deposition to the Chesapeake Bay and to its Watershed (~1999)(linear graph)
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direct dep to Ches Bay
5 % of WS dep
10 % of WS dep
25 % of WS dep
0 50 100 150 200 250 300kg Hg deposited per year
municipal waste incinmedical waste incinother waste incin
metallurgicalcement/concrete
chemical/other manufacturingcoal-fired elec generation
oil combustion (non-mobile)all other fuel combustion
What is Relative Importance of Hg Deposited Directly to Chesapeake Bay Surface vs. Deposition to Watershed (?)
Depends on what %of WS-deposited Hgmakes it into the Bay...
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Some Next Steps
Expand model domain to include global sources
Additional model evaluation exercises ... more sites, more time periods, more variables (e.g., not just wet deposition).
Sensitivity analyses and examination of atmospheric Hg chemistryin the marine boundary layer and at upper elevations...
Simulate natural emissions and re-emissions of previously deposited Hg
Use more highly resolved meteorological data grid
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Current (2004) Monitoring Sites in
Chesapeake BayRegion (incomplete?)