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New England Coastal Basins Mercury Deposition Network
WET DISTRIBUTION OF MERCURY IN THE BOSTON METROPOLITAN AREA
National Atmospheric Deposition Program meeting, October 20-24, 2003, Washington D.C.
Ann Chalmers1, Mark Nilles2, David Krabbenhoft3, Eric Prestbo4, and Mark Olson3
1 U.S. Geological
Survey, P.O. Box 628, Montpelier, VT 05601, T: 802-828-4511; F: 802-828-4465;
Atmospheric deposition is the dominant source of mercury (Hg) input to terrestrial and aquatic ecosystems in New England. Stream water, sediment, and fish tissue data suggest relatively higher concentrations of mercury in urban areas around Boston, however, most of the previously existing deposition sites have been located in rural areas. In 2002, the U.S. Geological Survey, in collaboration with Frontier Geosciences, the New Hampshire Department of Environmental Services, and the Blue Hill Observatory began a 2-year, four-site network to monitor Hg in wet deposition. The goals of the monitoring network are to (1) assist in interpretations of Hg concentrations in water, sediment, and fish tissue in the Boston area, (2) test a new wet atmospheric deposition sampler (N-CON) that has potential use in national, multi-agency atmospheric monitoring networks, and (3) provide total and methylmercury deposition data in more urban areas of New England. Three of the 4 sites are in urban areas around Boston, the fourth is in a rural area of central New Hampshire. One N-CON collector is co-located at a NADP-MDN network site for comparison between the N-CON and the modified Aerochem collectors used by NADP.
Preliminary results from this investigation found that concentrations of total Hg in wet deposition during 2002 ranged from 2-20 ng/L (nanograms per liter) at the 4 sites. Median concentrations of Hg in the 3 urban areas around Boston were 8.8, 7.2 and 7.8 ng/L respectively, compared to 5.7 ng/L in rural New Hampshire. These results suggest that localized urban emission sources may have significant effects on concentrations of Hg in rainfall in New England, and may result in variable deposition patterns on a sub-regional scale.