Monday, November 13, 2006 - 9:45 AM
108-3
The Distribution of Mercury in a Forest Floor Transect.
Charles Perry1, Michael Amacher1, William Cannon2, Randall Kolka3, and Laurel Woodruff2. (1) USDA Forest Service, 1992 Folwell Avenue, St. Paul, MN 55108, (2) US Geological Survey, 954 National Center, Reston, VA 20192, (3) USDA-Forest Service NC Res. Station, 1831 E US Highway 169, Grand Rapids, MN 55744
Upland soils are sinks for mercury. Some of these sink properties may be due to storage or volatilization. Climatic factors influencing microbial activity may also increase retention. As industrial emissions come under increasing regulation, the contribution of other sources to the mercury budget is an increasingly significant unknown. We constructed a spatial model of the mass of forest floor mercury along a transect spanning the northern coterminous United States. We measured the mercury concentration in forest floor samples collected by the USDA Forest Service Forest Inventory and Analysis program. The samples were distributed across 18 different ecoprovinces of the central United States. Approximately 1300 samples were processed by a USDA Forest Service lab in Logan, UT, and a lab under contract with the US Geological Survey. The laboratories follow national standards and test duplicates and blanks for QA/QC analysis. This concentration data was combined with the total mass and depth of the forest floor to estimate the mass of mercury stored in the forest floor. We begin with two hypotheses. First, we hypothesized that the distribution of Hg is not uniform across the central United States. We predicted greater deposition in the northeast in response to climate patterns and the distribution of sources. Second, we hypothesized that even within one ecoprovince, Hg pools would not be uniform between different forest types. The chemical properties of the forest floor affect Hg storage. Preliminary analyses suggested that the concentration of Hg increased with latitude. Also, the highest concentrations were observed in the northeastern corner of our region of interest. Additional analyses will test the statistical significance of these observations.