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Mercury in the West*. Land and Water Fund of the Rockies and Rocky Mountain Office of Environmental Defense January 2003.

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Mercury in the West*

Land and Water Fund of the Rockies

and

Rocky Mountain Office of Environmental Defense

January 2003

*The information in this presentation is largely drawn from the white paper “A Closer Look at Mercury in the West” prepared by Paulette Middleton for the Land and Water Fund of the Rockies and Environmental Defense (http://panoramapathways.net/mercuryinthewest.pdf)


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Mercury Overview

  • Hg is present in the earth’s atmosphere in the form of elemental vapor, reactive (i.e., oxidized) gaseous Hg, and particulate Hg

  • Hg that gets into aquatic ecosystems through atmospheric deposition or soil runoff can be transformed into an extremely toxic organic methylmercury which bioaccumulates up the food chain as humans and animals consume contaminated organisms such as fish


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Mercury Overview - II

  • Children and fetuses, because they are in rapid developmental stages, are particularly susceptible to the harmful neurological effects of methylmercury

  • In a 2000 report, the National Academy of Sciences’ National Research Council estimated that each year about 60,000 children may be born in the U.S. with neurological problems that could lead to poor school performance because of exposure to methylmercury in utero


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Mercury Fate and Transport

  • Because of differences in the forms of Hg and its transport behavior, populations can be placed at risk from Hg that may have come from local sources, a different state, or a different part of the world

  • In the US, both the West and East are source regions of mercury as well as affected areas


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Mercury Fate and Transport - II

  • The more reactive gaseous forms of Hg can be deposited on land and water much closer to the sources

  • Elemental Hg can persist in the atmosphere and be transported longer distances, but is a substantial contributor to Hg concentrations in land and water especially in remote areas where atmospheric transport is the main mechanism of contamination

  • All airborne Hg also can undergo chemical reactions that lead to Hg compounds that are more readily deposited


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Mercury Fate and Transport – IIILong-range vs. Short-range

  • Quantification of transport is a matter of on-going investigation

  • Grumet (former NESCAUM) estimates that 47% of Hg deposited in the Northeast comes from within that region, 30% from other US sources and 23% from global sources (http://www.eerc.und.nodak.edu/catm/graphics/v7i1part2.pdf)

  • Levin suggests that Hg deposition is concentrated in areas close to sources, that Asian emissions account for 10-20% of deposition on the West Coast, and that non-anthropogenic sources contribute 4-7% in the East and 10-12% in the West (same cite)

  • Based on modeling, Bullock (NOAA) estimates that 25-30% of the deposition in the US comes from global background, the rest from US sources (http://pubs.acs.org/hotartcl/est/98/apr/mer.html)

  • Comparing lake sediment core samples from MN and coastal AK, Swain (MN Pollution Control Agency) estimates that 40% of Hg is due to regional anthropogenic sources (same cite)

  • Modeling analysis by Seigneur (AER, Inc.) suggests that global background accounts for about 70% of Hg deposition in the US


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Sources of U.S. Anthropogenic HgSource: EPA Mercury Report to Congress (1997)

  • About 158 total tons of Hg are emitted in the US each year

  • 4 source categories are responsible for about 80% of total anthropogenic Hg:

    • Coal-fired utilities are largest source at 33%

    • Municipal waste combustors (19%)

    • Commercial/industrial boilers (18%)

    • Medical waste incinerators (10%)

  • Coal-fired power plants are largest uncontrolled anthropogenic source of Hg


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Coal-fired Power Plant Hg Emissions

  • US Coal-fired units emitted 48 tons of Hg in 1999

  • Speciation: about 3% particulate, 43% reactive gaseous, and 54% elemental

  • Breakdown varies from plant-to-plant depending on type of coal being burned and emission controls in place

  • Total Hg emissions are higher in the East than in the West, as expected, since utility emissions are much higher in the East

  • NM is highest in West and ranks 15th nationally

    Source: EPA 1999 Information Collection Request


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Western Coal-fired Power Plant Hg EmissionsSource: EPA 1999 Information Collection Request


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The West Has High Levels of Mercury Contamination

  • Although there are limited monitoring sites in the West, recent observations of Hg concentration and deposition indicate that Hg levels in the West are similar to those in the East

  • In fact, New Mexico had the highest average atmospheric Hg concentration in U.S. for 2000

  • Colorado had a high total wet deposition level in 2000, comparable to eastern monitoring sites

    SOURCE: National Atmospheric Deposition Program, Mercury Deposition Network


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Annual Average Mercury Atmospheric Concentrations, 2000

National Atmospheric Deposition Program, Mercury Deposition Network


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Total Annual Mercury Wet Deposition, 2000

National Atmospheric Deposition Program, Mercury Deposition Network


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Hg Monitoring in the West

  • The western NADP sites indicated on the preceding maps are:

    • Buffalo Pass, Routt County, Colorado

    • Caballo, Sierra County, New Mexico

    • Seattle, King County, Washington

    • San Jose, Santa Clara County, California

    • Covelo, Mendocino County, California


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Fish and Wildlife Advisories

  • If high concentrations of Hg or other chemicals are found in local fish and wildlife, states or tribes may issue a consumption advisory

  • Virtually every western state (except Wyoming) had active fish consumption advisories for specific water bodies in 2000




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Western Mercury Advisories Pollutant – 2000

  • The table in word format accompanying this presentation lists mercury advisories for waterbodies in western states

  • Advisories are in effect for waterbodies across the West


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Mercury Control Options for Pollutant – 2000 Western Power Plants

  • The EPA Information Collection Request analysis indicates that subbituminous coals emit relatively more elemental Hg than bituminous coals

  • Both elemental and reactive gaseous Hg can be absorbed onto porous solids such as fly ash, powdered activated carbon or calcium-based acid gas sorbents for subsequent collection in a PM control device such as a fabric filter


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Mercury Control Options – II Pollutant – 2000Western Power Plants

  • Powdered activated carbon (PAC) injection has been successfully demonstrated for about 10 years on med waste incinerators, mun waste combustors and haz waste combustors

  • The activated carbon is injected before the fabric filter and, if necessary, a water mist used to cool the flue gas

  • In cases where a spray dryer fabric filter system is used, the gas cooling occurs in the spray dryer and no mist is necessary


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Mercury Control Options – III Pollutant – 2000Western Power Plants

  • The EPA Information Collection Request data also indicate that chemistry associated with the selective catalytic reduction (SCR) systems may be enhancing the oxidation of Hg and, as a result, increasing capture efficiency

  • How it Works: SCR processes designed to reduce NOx by converting NOx to N2 can enhance the oxidation of Hg to forms that are more readily captured


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