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

• Modeling Methodology

• Hg Emissions Inventory

• Model Evaluation

• Some Results for Chesapeake Bay

• Some Next Steps

Modeling Methodology

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?

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

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

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

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

MercuryEmissionsInventory

Estimated 1999 U.S. Atmospheric Anthropogenic Mercury Emissions

Estimated Speciation Profile for 1999 U.S.Atmospheric Anthropogenic Mercury Emissions

Estimated 2000 Canadian AtmosphericAnthropogenic Mercury Emissions

Geographic Distribution of Estimated Anthropogenic Mercury Emissions in the U.S. (1999) and Canada (2000)

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)

1995 Global Hg Emissions Inventory Josef Pacyna,NILU, Norway (2001)

ModelEvaluation

Mercury Deposition Network Sites with 1996 data in the Chesapeake Bay Region

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

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

1999 Results forChesapeake Bay

Geographical Distributionof 1999 Direct Deposition

Contributions to the Chesapeake Bay (entire domain)

Geographical Distribution of 1999 Direct Deposition Contributions to the Chesapeake Bay (regional close-up)

Geographical Distribution of 1999 Direct Deposition Contributions to

the Chesapeake Bay (local close-up)

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

Largest Regional Individual Sources Contributing to1999 Mercury Deposition Directly to the Chesapeake Bay

Largest Local Individual Sources Contributing to1999 Mercury Deposition Directly to the Chesapeake Bay

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

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)

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)

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...

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

Current (2004) Monitoring Sites in

Chesapeake BayRegion (incomplete?)