Mercury Deposition Network
The USGS in cooperation with researchers at the George Mason University Department of Chemistry, operate a mercury deposition precipitation sampler in Culpeper, Virginia. The site is part of the Mercury Deposition Network (MDN), a cooperative U.S. and Canadian network of mercury wet deposition samplers deployed to characterize mercury deposition via rain and snow (i.e., wet deposition). The sampler has been running continuously since November of 2002 and was modified to collect samples for trace metal analysis beginning in November of 2004 (Figure 1).
Figure 1. View of the VA-08 MDN site showing the recording rain gauge (foreground) and an MDN precipitation collector (background). Precipitation samples are collected through one of two chimneys on the left side of the collector (one for mercury and one for other trace metals) when the moisture sensor activates the lid covering the sample chimneys. Photo by Allan Kolker, USGS.
Data generated from the sampler include weekly mercury and trace element concentration and deposition. These data show variations in mercury and other trace metal wet deposition across the country (Figure 2). Statistical and air mass trajectory modeling are being used to identify potential sources for the mercury and other trace metals, and suggest processes important in controlling wet deposition. Data from the VA-08 site are also being compared to data from the nearby Shenandoah National Park-Big Meadows MDN site (VA-28). The sites are within 31 kilometers of one another but vary in elevation (VA-08 = 183 m; VA-28 = 1,074 m) allowing for investigation on the effect of elevation on deposition.
Figure 2. MDN results for 2004, including the Culpeper VA-08 site. Warmer colors indicate areas of higher wet deposition while cooler colors represent lower yearly deposition. Mercury deposition and concentration maps available from the National Atmopsheric Deposition Program – Mercury Deposition Network.
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