Wet Deposition of Mercury In The U.S.

Results from the NADP Mercury Deposition

Network, 1996-2004

David Gay

Illinois State Water Survey, Champaign, IL,

dgay@uiuc.edu217.244.0462

Goal of this Presentation….

To introduce you to the Mercury Deposition Network.

Show what we know about the deposition of mercury.

What is the Mercury Deposition Network?

A Cooperative Research Program

Part of National Atmospheric Deposition Network 92 sites Federal, State, Local and Tribal Governments

members, private organizations Measuring wet deposition of mercury

Our Charge: to determine if trends exist in wet deposition of

mercury over time

Federal Agency Members

University Members

Tribal Organizations             

Other Organizations

and States

Why monitor Mercury in Precipitation?

Why monitor Mercury in Precipitation?

Atmospheric transport and deposition is the dominant pathway to most aquatic ecosystems.

Between 50 and 75% of the mercury input to lakes and streams is by wet deposition (probably less in the West).

Mercury Emissions Contribute to Exposure to Mercury

• The primary pathway of human exposure to mercury in the U.S. is through eating contaminated fish.• Power plants emit approximately 48 tons of mercury and are the largest source of mercury emissions in

the U.S. (approximately 41%).

Wet and Dry Deposition

Emissions and

Speciation

AtmosphericTransport and

Deposition

Ecosystem Transport, Methylation, and Bioaccumulation

Consumption Patters

Human Exposure

Fishing• commercial• recreational • subsistence

Mercury transforms into methylmercury in soils and water, then can bioaccumulate

in fish

Atmosphericdeposition

Impacts • Best documented

impacts on the developing fetus: impaired motor and cognitive skills

• Possible cardiovascular, immune, and reproductive system impacts

Emissions to the Air

Humans and wildlife affected primarily by eating contaminated fish

Ocean

methylation

Lake

methylation

From Ellen’s Presentation…..

How Mercury is Wet Deposited

Hgo

RGMHgp

Hgp

RGM

Atmospheric Mercury Species Abundance

Hg0 – Elemental Mercury

RGM – Reactive Gaseous Mercury

Hgp – Particulate Bound Mercury

Typical Atm. Mercury Species Abundance

1.4-1.81.4-1.8ng/mng/m33

How Mercury is Wet Deposited

oxidationHgo

RGM

Picture of the sampler here

MDN Sites(2005)

What the Data Show….

Mercury Concentrations in Precipitation2003

Mercury Concentrations in Precipitation

Mercury Wet Deposition, 2003

Regional Average Mercury Concentrations

0.02.04.06.08.0

10.012.014.016.018.0

Win Spr Sum Fall

Season

Con

c. (n

g/L)

MW NE NW SE SW

Regional Average Mercury Deposition

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Win Spr Sum Fall

Season

Dep

. (ug

/m2)

MW NE NW SE SW

Possible Reasons for High Mercury Deposition in the Summer

Higher rainfall amounts Higher temperatures Higher oxidant levels Southerly air flow Strong thunderstorms Higher emissions (ocean)

WET DEPOSITIONModeled and Measured

Seigneur and others, ES&T, 2004, V38, 555-569

Trends In Wet Deposition

Trends

Seasonal Kendall and Sen’s (non-parametric)

5 years of data for 4 seasons Run seasonally Very small, slight changes, but

none significant

Dry Deposition

Measurements of Dry Deposition

?•Very few measurements•Very few calculations of dry deposition

DRY DEPOSITION

Seigneur and others, ES&T, 2004, V38, 555-569

Modeling Deposition

Sampling box for

manual system

Monitoring station for manually-operated sampling system

Plans for Dry Deposition Manually Operated Mercury Species

Sampling

EPA Method IO-5Gold-Trap Method for Hg0 i

Automated Hg Speciation

Methods are:-Lab Tested-Widely used-QA

challenged-EPA Accepted

PHg

RGM

Hg0

Future Directions for MDN

Expand network coverage in the western U.S., southern Canada, and Mexico

Provide “before” and “after” mercury deposition data related to future controls on mercury emissions

Develop better methods to monitor dry deposition of mercury

Monitor additional trace metals

Wet Deposition of Mercury In The U.S.

Results from the NADP Mercury Deposition

Network, 1996-2004

David Gay

Illinois State Water Survey, Champaign, IL,

dgay@uiuc.edu217.244.0462

Anthropogenic Sources of Mercury

Coal combustion Incineration

Medical Trash Cremation

Industrial emissions (chlor-alkali) Cement production (Hg in lime) Hg use in gold and silver mining (amalgam formation) Mining of Hg Automobile Recycling Mercury in Landfills

Fluorescent lamps dental amalgams (also in sewers) Thermometers Batteries Discarded electrical switches

Others will surface Other carbon fossil fuels (gas/oil/diesel)?

Natural Sources of Mercury

Volcanoes (St. Helens) Naturally enriched ores/soils

Plate tectonic boundaries Cinnabar (HgS), taconite, others

Soils and rocks (0.5 ppm in crust) Evaporation

Soils Fresh water and OCEANS

Natural forest fires (wood fire places?) Mine tailings Tree bark, volatilization from rocks?

Many Mercury Sources

Coal combustion Incineration Industrial emissions

(chlor-alkali) Cement production

(lime) Hg use in mining and

Mining of Hg Automobile Recycling

Mercury in Landfills Fluorescent lamps dental amalgams (also

in sewers) Thermometers, batteries electrical switches

Taconite

Volcanoes (St. Helens) Enriched ores/soils

Tectonic (plate) boundaries

Cinnabar (HgS), taconite, others

Soils and rocks (0.5 ppm in crust)

Evaporation Soils Fresh water and Oceans

Forest fires (wood fire places?)

Tree bark, volatilization from rocks?