HR: 17:30h
AN: B14B-06    [Abstracts]
TI: The Influence of Wetland Cover and Dissolved Organic Carbon on Mercury Export in Forest Landscapes, Northeastern USA
AU: Dittman, J A
EM: jadittma@syr.edu
AF: Department of Civil and Environmental Engineering, 151 Link Hall, Syracuse University, Syracuse, NY 13244, United States
AU: * Shanley, J B
EM: jshanley@usgs.gov
AF: U.S. Geological Survey, P.O. Box 628, Montpelier, VT 05601, United States
AU: Driscoll, C T
EM: ctdrisco@syr.edu
AF: Department of Civil and Environmental Engineering, 151 Link Hall, Syracuse University, Syracuse, NY 13244, United States
AU: Aiken, G
EM: graiken@usgs.gov
AF: U.S. Geological Survey, 3215 Marine Street, Boulder, CO 80303, United States
AU: Chalmers, A
EM: chalmers@usgs.gov
AF: U.S. Geological Survey, P.O. Box 628, Montpelier, VT 05601, United States
AU: Towse, J
EM: jetowse@plymouth.edu
AF: Center for the Environment, 205 Boyd Science Center, Plymouth State University, Plymouth, NH 03264, United States
AB: Mercury (Hg) contamination is widespread in remote areas of the northeastern USA. Atmospheric Hg is deposited on terrestrial uplands and subsequently mobilized to downstream aquatic ecosystems. We are investigating the fate of Hg deposited in forested watersheds by quantifying stream transport of Hg, and the interactions with dissolved and particulate organic matter. We hypothesize that the landscape characteristics controlling the production and mobility of organic matter will likewise control the mobility of Hg. This research was conducted at three sites in the Northeast that represent a range of hydrochemical conditions and span a range of wetland cover. Most stream export of Hg occurs at high flow; therefore we collected samples during snowmelt and storms. Mercury concentrations increase with discharge at all three sites; however the partitioning of Hg fractions (dissolved vs. particulate) differs among sites during high flow events. At the Hubbard Brook Experimental Forest, NH (watershed 6), there are no true wetlands and dissolved organic carbon (DOC) and total Hg (THg) concentrations, and suspended sediment concentration (SSC) (mean DOC = 3.1 mg C L^-1; THg = 1.5 ng L^-1; SSC < 50 mg L^-1) are low even during the highest of flow events. At Sleepers River, VT (watershed 9), SSC can be elevated during events (SSC > 500 mg L^-1), consequently the particulate Hg fraction can range as high as 95% of the THg concentration (mean particulate Hg concentration = 10.2 ng L^{- 1}). At Archer Creek (Huntington Forest, NY), which has the greatest percent wetland cover (10%) of our three sites, DOC concentrations are high (mean DOC = 7.5 mg C L^-1), while SSC are low (SSC < 10 mg L^{- 1}). At Archer Creek, Hg is largely in the dissolved form (~75% of Hg) and strongly correlated with DOC (r² = 0.90). The hydrophobic organic acid (HPOA) fraction of DOC is most effective at mobilizing Hg and is strongly correlated to Hg concentrations in stream water. This research suggests that high concentrations of Hg can be present in stream water from forest watersheds during high flow events, and that wetlands and suspended sediment favor Hg export. However, it is not clear to what degree this Hg is bioavailable for potential uptake by organisms in aquatic ecosystems following mobilization.
DE: 0400 BIOGEOSCIENCES
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting