atmospheric mercury modeling 101 mark cohen air resources laboratory arl 101 june 19, 2012...

Air Resources Laboratory 1

Atmospheric Mercury Modeling 101

Mark CohenAir Resources Laboratory

ARL 101June 19, 2012

6/19/2012

6/19/2012 Air Resources Laboratory 2

In many waterbodies – including the Great Lakes and Gulf of Mexico -- levels of mercury in some fish are too high for safe consumption by humans and wildlife

Air Resources Laboratory 36/19/2012

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Aver

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Mer

cury

Con

cent

ratio

n (p

arts

per

mill

ion

by w

eigh

t)Mercury Concentrations in Gulf of Mexico Seafood Species

approximate concentrationin light tuna – can have 12 oz per week


In many waterbodies – including the Great Lakes and Gulf of Mexico -- levels of mercury in some fish are too high for safe consumption by humans and wildlife

For many waterbodies, atmospheric deposition is the largest loading pathway for mercury

For a given waterbody, where does the mercury come from that is deposited?

Atmospheric mercury emitted from other regional and more

distant sources

wet deposition: pollutants brought down to the earth’s surface in rain and snow

dry deposition: pollutants brought down to the earth’s surface in the absence of rain or snow

Gaseous pollutants can be absorbed by the surface

Particles with pollutants on them can “fall” to the surface

Large Point Sources of Mercury Emissions Based on the 2002

EPA NEI and2002 Envr Canada NPRI*

size/shape of symbol denotes amount of mercury emitted (kg/yr)

5 - 10 10 - 50 50 - 100

100 – 300

300 - 500

500 - 1000

color of symbol denotes type of mercury source

coal-fired power plants

other fuel combustion

waste incineration

metallurgical

manufacturing & other

1000 - 3000

* Note – some large Canadian point sources may not be included due to secrecy agreements between industry and the Canadian government.

2002 U.S. and Canadian Emissions of Total Mercury [Hg(0) + Hg(p) + RGM]

There are a lot of sources!


Anthropogenic Mercury Emissions (ca. 2005)

Dry and wet deposition of the pollutants in the puff are estimated at each time step.

The puff’s mass, size, and location are continuously tracked…

Phase partitioning and chemical transformations of pollutants within the puff are estimated at each time step

= mass of pollutant(changes due to chemical transformations and deposition that occur at each time step)

Centerline of puff motion determined by wind direction and velocity

Initial puff location is at source, with mass depending on emissions rate

TIME (hours)0 1 2

deposition 1 deposition 2 deposition to receptor

lake

Lagrangian Puff Atmospheric Fate and Transport ModelNOAA HYSPLITMODEL

one Hg emissions

source

Beltsville monitoring

site

Model-predicted hourly mercury deposition (wet + dry) in the vicinity of one example Hg source for a 3-day period in July 2007

100 - 1000 10 – 100 1 - 100.1 – 1

* hourly deposition converted to annual equivalent

deposition(ug/m2)*

Washington D.C.

NOAA Silver Spring

one Hg emissions

source

Model-predicted hourly mercury deposition (wet + dry) in the vicinity of one example Hg source for a 3-day period in July 2007

100 - 1000 10 – 100 1 - 100.1 – 1

* hourly deposition converted to annual equivalent

deposition(ug/m2)*

Washington D.C.

Large, time-varying spatial gradients in deposition & source-receptor relationships

Beltsville monitoring

site

NOAA Silver Spring

Geographical Distribution of 2005 Atmospheric Mercury Emissions (Natural + Re-emit + Direct Anthropogenic)

Policy-Relevant Scenario Analysis

Here’s where the mercury is emitted from...

But what is the relative importance of different source regions to atmospheric deposition of mercury to the Great Lakes?

Does most of it come from China?

Presentation to IJC-IAQAB, Apr 25, 2012NOAA Air Resources Laboratory 13

Geographical Distribution of 2005 Atmospheric Mercury Deposition Contributions to Lake Erie

Policy-Relevant Scenario Analysis

Here’s where the mercury came from that was deposited to Lake Erie (~2005)


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cury

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Distance of Emissions Source from the Center of Lake Erie

Emissions from Natural Sources

Emissions from Re-Emissions

Emissions from Anthropogenic Sources

A tiny fraction of 2005 global mercury emissions within 500 km of Lake Erie

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Distance of Emissions Source from the Center of Lake Erie

Contributions from Natural Sources

Contributions from Re-Emissions

Contributions from Anthropogenic Sources

Modeling results show that these “regional” emissions are responsible for a large fraction of the modeled 2005 atmospheric deposition

Important policy implications!


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anthropogenic re-emissions from land

direct anthropogenic emissions

Model-estimated 2005 deposition to the Great Lakes Basin from countries with the highest modeled contribution from direct and re-emitted anthropogenic sources


Modeling needed to help interpret and extend measurements and to estimate source-receptor relationships

Monitoring needed to ground-truth models and provide solid deposition estimates at specific locations

To get the answers we need, we need to use both monitoring and modeling -- together


Extra Slides

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Mercury Concentration(parts per million)

Om

eg

a II

I Fa

tty

Ac

ids

(g

ram

s pe

r 3

oz s

ervi

ng)

TilefishShark

Swordfish

King MackerelRed Snapper

Grouper

Orange Roughy

Tuna (fresh or frozen)

Lobster

Halibut

Herring

Salmon

Mahi Mahi

Oysters

Clams

Shrimp

Flounder or SolePollock

Graph based on data presented by the American Heart Association -- http://www.americanheart.org

* canned, light

Cod

Tuna*Crabs

CatfishScallops

Fish concentration data from NOAA and FDA. Downloaded Sept 2008 from the EPA-FDA fish-mercury website: http://www.cfsan.fda.gov/~frf/sea-mehg.html

Mercury Levels in Commercial Fish and Shellfish

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Hg

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en

tra

tio

n (

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x

300 - 700

100 - 30050 - 10010 - 50 1 - 10

Number of Samples“error bars” show range of mercury concentrations in data for a given species

What Influences Hg Levels in Fish?

Current / past atmospheric and other Hg inputs to the fish’s ecosystem

Food web structure of the waterbody and trophic level of species

Biogeochemical factors influencing the degree of mercury methylation in the ecosystem (sulfate, dissolved organic carbon, pH, etc)

Age (size) of fish – as fish age, they accumulate more and more mercury

History of that particular fish

Note – Hg in fish muscle tissue, so can’t easily avoid it (PCB’s, Dioxins and other hydrophobic contaminants concentrated in fat)

Knowledge gaps for Hg levels and reasons for levels:o freshwater (inland) fish -- LARGEo estuarine & marine fish -- VERY LARGE

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Swordf

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Clams

Met

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Mean Methylmercury Concentrations for "Top 24" Types of Fish Consumed in U.S. Commercial Seafood Market

Source of data: Carrington and Bolger, 2002Based on slide from: Elsie Sunderland,

USEPA

Percent Contribution to per capita Methylmercury Intake by Fish Type for "Top 24" Types of Fish in U.S. Commercial Seafood Market

Source of data: Carrington and Bolger, 2002Based on slide from: Elsie Sunderland,

USEPA

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Fish Type

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.S.

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†Estimate based on the product of per capita fish consumption rates and mean methylmercury concentrations of each type of fish (Carrington and Bolger, 2003)

Sunderland, E. (2007). Mercury exposure from domestic and imported estuarine and marine fish in the U.S. seafood market. Environ Health Perspect 115(2):235-42.

Seafood consumption estimated in this study

from NMFS fisheries supply data compared with available data for

marine and estuarine fish consumption from CSFII

dietary survey data [uncooked weights

(U.S. EPA 2002].

Percentage of total Hg intake (product of

seafood supply and Hg concentrations) for the

top 15 seafood categories; intake is

allocated by the source region for each of the

fisheries products [Atlantic, Pacific, imported (foreign

sources), and high seas landings].

U.S. Population-Wide Consumption & Hg Exposure for Marine and Estuarine Fish

Source: Gary Ginsberg, Connecticut Dept of Public Health (2007). “Risk-Benefit Synthesis for Fish Consumption Advisories,” presented at National Forum on Fish Contaminants, Portland, ME. http://www.epa.gov/waterscience/fish/forum/2007/pdf/section2f.pdf

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es B

asin

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erso

n)

anthropogenic re-emissions from land

direct anthropogenic emissions

Model-estimated per capita 2005 deposition to the Great Lakes Basin from countries with the highest modeled contribution from direct & re-emitted anthropogenic sources


Modeling – ApproachesBack-trajectory analyses with HYSPLIT

Fate and transport modeling with HYSPLIT-Hg


…focus on source-receptor relationships


Back Trajectory Analysis – Episodes

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mercury site

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Chesap

eake

BayBaltimore

Washington D.C.

North American mercury sources

mercury that doesn’t

deposit continues

its global circulation

*

regional and and global

sources contribute to atmospheric

mercury deposition

30

mercury from global

atmospheric pool entering

North America

Thousands of fish-advisories throughout North America due

to mercury contamination

Polar-specific air-chemistry can lead to enhanced

mercury deposition under some conditions

Atmospheric mercury deposition varies spatially and temporally, and is always a complex combination of impacts from local, regional, national, and global emissions sources.

Air Resources Laboratory6/19/2012


Different “forms” of mercury in the atmosphere

Elemental Mercury -- Hg(0)• most of total Hg in atmosphere• doesn’t easily dry or wet deposit• globally distributed

Reactive Gaseous Mercury -- RGM• a few % of total atmos. Hg• oxidized Hg (HgCl2, others)

• very water soluble and “sticky”• bioavailable

Particulate Mercury -- Hg(p)• a few % of total atmos. Hg• Hg in/on atmos. particles• atmos. lifetime 1~ 2 weeks• bioavailability?

?

Elemental Mercury -- Hg(0)• most of total Hg in atmosphere• doesn’t easily dry or wet deposit• globally distributed

Reactive Gaseous Mercury -- RGM• a few % of total atmos. Hg• oxidized Hg (HgCl2, others)

• very water soluble and “sticky”• bioavailable

Particulate Mercury -- Hg(p)• a few % of total atmos. Hg• Hg in/on atmos. particles• atmos. lifetime 1~ 2 weeks• bioavailability?

?


Modeling – Comprehensive Fate and Transport Simulations

Start with an emissions inventory

Use gridded meteorological data

Simulate the dispersion, chemical transformation, and wet and dry deposition of mercury emitted to the air

Source-attribution information needed at the end, so optimize modeling system and approach to allow source-receptor information to be captured

HYSPLIT-Hg developed over the last ~10 years with specialized algorithms for simulation of atmospheric mercury

Air Resources Laboratory 33

Provide sound scientific information on the emission, dispersion, transformation, and air-surface exchange of atmospheric mercury compounds

Measure and understand spatial and temporal trends in air concentrations and air-surface exchange

Provide robust source-attribution information for atmospheric mercury deposition to sensitive ecosystems, to inform policies to reduce loadings

6/19/2012

Mercury exposure via fish consumption is an important public health concern

NOAA has a primary stewardship responsibility for the nation’s fisheries

Atmospheric emissions and subsequent deposition is a significant pathway through which mercury contamination enters sensitive aquatic ecosystems

Context

Goals


Modeling used to aid in data interpretation and measurement planning

Measurements used for model evaluation and

improvement

Mercury: Measurements and Modeling

speciated atmospheric mercury

other air pollutants, e.g., SO2, O3, CO

wet deposition air-surface exchange

MEASUREMENTS

back trajectories

comprehensive fate and transport

MODELING

source-attribution for deposition

Mercury transformed by bacteria into methylmercury in sediments, soils & water, then bioaccumulates in fish

Humans and wildlife affected primarily byeating fish containing mercury

Best documented impacts are on the developing fetus: impaired motor and cognitive skills

atmospheric deposition to the watershed

atmospheric depositionto the water surface

adapted from slides prepared by USEPA and NOAA

Environmental Mercury Cycling -- Natural vs. Anthropogenic

This has always been going on, ... always has been Hg in fish

Mercury (Hg) is an element... there is the same amount of mercury on Earth today as there always has been

“natural” Hg cycle: o transported throughout the

environment

o chemical transformations interconvert different mercury species

Sunderland and Mason (2007). Global Biogeochemical Cycles 21, 4022

Pre-Industrial Global Mercury Cycling

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10

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extraction from deep reservoirs,

e.g., volcanoes

naturaldep to ocean

106

molesper

year natural dep to land

naturalevasion

fromocean

naturalevasion

fromland

pre-industrial: total mercury in atmosphere ~

8.0 x 106 moles

Based on data presented in Sunderland and Mason (2007) Global Biogeochemical Cycles 21: GB4022

(note -106 moles ~ 200 metric tons)GLOBAL MERCURY CYCLING

Environmental Mercury Cycling -- Natural vs. Anthropogenic

Most anthropogenic Hg is “released” as atmospheric emissions: Hg in coal is released to the air when coal is burned Hg in other fuels is released to the air when they are processed and burned Hg in ores is released to the air during metallurgical processes Hg in products is released to the air when burned or landfilled after being discarded

(e.g., batteries, switches)

This has always been going on, and there has always been Hg in fish

Mercury (Hg) is an element... there is the same amount of mercury on Earth today as there always has been

“natural” Hg cycle – Hg is transported throughout the environment, and chemical transformations interconvert different mercury species

But, we make some Hg unexpectedly “bioavailable”

Average, current atmospheric Hg deposition is ~3x pre-industrial levels

Evidence suggests that newly deposited Hg is more bioavailable

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-10

0

10

20natural

extraction from deep reservoirs,

e.g., volcanoes

naturaldep to ocean

106

molesper

year natural dep to land

naturalevasion

fromocean

naturalevasion

fromland

pre-industrial: total mercury in atmosphere ~

8.0 x 106 moles

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-10

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20anthropdirect emit

anthropre-emit

fromocean

anthropdep to land anthrop

dep to ocean

anthropre-emit

fromland106

molesper

year

contemporary: total mercury in atmosphere ~

28.0 x 106 moles

Based on data presented in Sunderland and Mason (2007) Global Biogeochemical Cycles 21: GB4022

(note -106 moles ~ 200 metric tons)GLOBAL MERCURY CYCLING

Freemont Glacier, Wyoming

source: USGS, Shuster et al., 2002

Natural vs. anthropogenicmercury?

Studies show that anthropogenic activities have typically increased bioavailable Hg concentrations in ecosystems by afactor of 2 – 10

Hg from other sources: local, regional & more distant

Measurement of ambient air

concentrations

Measurement of wet

deposition

atmospheric mercury modeling 101 mark cohen air resources laboratory arl 101 june 19, 2012...

Documents

levels of mercury

atmospheric deposition

atmospheric mercury

mercury emitted kgyr

type of mercury sourcecoal

snowdry deposition

arls mercury research

distant sources wet