MERCURY AND METAL WET DEPOSITION IN COASTAL SOUTHERN NEW HAMPSHIRE

Although the northeastern United States has been labeled as an area of high mercury deposition by several groups (e.g., VanArsdale et al., Ecotoxicology, 2005), few studies have linked high mercury deposition to individual pollution events or have discerned the contributions of different sources to the regional budget. These correlations are in part difficult because they require high-resolution monitoring associated with ongoing measurements of other atmospheric chemical parameters (e.g., Total Gaseous Mercury, CO, CO₂, O₃, and particulate concentrations). To address these concerns, the Atmospheric Investigation, Regional Modeling, Analysis and Prediction (AIRMAP) program initiated the analysis of wet deposition at their Thompson Farm (TF) site in Durham, NH. Our preliminary 2006 data support the notion of higher Hg loadings at the beginning of storms and in smaller rain volumes. The average summer 2006 deposition for Thompson Farm is over 3.6 μg m^-2, a value comparable to but higher than the three-site summer 2004-2005 average for Maine sites ME96, ME98, ME02 in the Mercury Deposition Network (MDN). The TF and ME96 sites showed the greatest total deposition during the summer periods studied as well as the highest deposition over sample intervals, concurrent with models of a Hg hot spot present along the eastern parts of the Maine/New Hampshire border. The Hg deposited by single storm events were highly variable, with the maximum load over 2 μg m^-2 . Back trajectories of the airmasses associated with the larger events generally travel through large metropolitan and/or industrial areas in the Midwest or along the Eastern Seaboard. Ongoing collection at our TF site, coupled with forthcoming analyses of trace metal data and examination of the 2006 MDN sites, will better explain temporal and variations in mercury loads and sources for Northern New England.