Atmospheric Mercury Measurements in the Gulf of Mexico and Mid-Atlantic Regions
United States Geological Survey,
Montpelier, VT USA
The presence of mercury in the environment, its wide distribution and cycling in coastal and aquatic ecosystems, and risks to human health constitute a major environmental resource management issue. The majority of mercury emitted to the environment is injected into the atmosphere through the combustion of fossil fuels, incineration of mercury-containing waste, and metallurgical processes (e.g., smelting). Wet and dry atmospheric deposition delivers mercury to sensitive aquatic ecosystems, where it can be converted to more toxic and bio-available forms such as methylmercury. Human exposure to methylmercury, which adversely affects the nervous system, results from consumption of contaminated fish and other organisms in the aquatic food web.
Despite mercury’s importance, however, many of the complex processes controlling its movement through the environment are poorly understood, and there is debate over the efficacy of emission controls in reducing mercury concentrations in estuarine and marine fish. In 2006 the National Atmospheric Deposition Program (NADP) introduced the Atmospheric Mercury Initiative to address many of these uncertainties. The initiative seeks to establish a network of sites to “…measure event-based mercury wet deposition, air concentrations of mercury in its gaseous and particulate forms, and meteorological and land-cover variables needed for estimating dry deposition fluxes [NADP, 2006].”
We present recent results from two such sites in the emerging network: a rural site at the Grand Bay National Estuarine Research Reserve (NERR) in Moss Point, MS, and a suburban site on the campus of the Beltsville Agricultural Research Center (BARC) in Beltsville, MD. The measured atmospheric mercury concentrations at the sites (elemental Hg(0), reactive gaseous mercury, and fine particulate mercury) will be summarized and compared with earlier results from 2007. Data will also be interpreted using ancillary measurements of primary (CO, NO/NOY, SO2) and secondary (O3) trace gases at each site; prevailing meteorology; and back trajectory analyses. Data collected in short-duration episodes of high mercury concentrations will be presented and discussed. Finally, results of studies designed to determine the role of sea salt aerosols in the marine environment will also be presented.