HR: 0800h
AN: B11B-0389    [Abstracts]
TI: Total Mercury and Methylmercury in the Great Egg Harbor River Watershed, New Jersey, USA
AU: Barringer, J L
EM: jbarringer@usgs.gov
AF: U.S. Geological Survey, New Jersey Water Science Center, 810 Bear Tavern Road, West Trenton, NJ 08628, United States
AU: Riskin, M L
EM: mriskin@usgs.gov
AF: U.S. Geological Survey, New Jersey Water Science Center, 810 Bear Tavern Road, West Trenton, NJ 08628, United States
AU: Szabo, Z
EM: zszabo@usgs.gov
AF: U.S. Geological Survey, New Jersey Water Science Center, 810 Bear Tavern Road, West Trenton, NJ 08628, United States
AU: * Fischer, J M
EM: fischer@usgs.gov
AF: U.S. Geological Survey, New Jersey Water Science Center, 810 Bear Tavern Road, West Trenton, NJ 08628, United States
AU: Reilly, P A
EM: jankowsk@usgs.gov
AF: U.S. Geological Survey, New Jersey Water Science Center, 810 Bear Tavern Road, West Trenton, NJ 08628, United States
AU: Rosman, R
EM: rrosman@usgs.gov
AF: U.S. Geological Survey, New Jersey Water Science Center, 810 Bear Tavern Road, West Trenton, NJ 08628, United States
AU: Bonin, J L
EM: jbonin@usgs.gov
AF: U.S. Geological Survey, New Jersey Water Science Center, 810 Bear Tavern Road, West Trenton, NJ 08628, United States
AU: Heckathorn, H A
EM: haheck@usgs.gov
AF: U.S. Geological Survey, New Jersey Water Science Center, 810 Bear Tavern Road, West Trenton, NJ 08628, United States
AB: Hydrologic and biogeochemical conditions are important factors in the transport and distribution of mercury (Hg) in New Jersey Coastal Plain watersheds that contain extensive freshwater wetlands and where Hg bioaccumulation is of concern. U.S. Geological Survey studies found Hg concentrations in top predator fish from the Great Egg Harbor River mainstem that ranged from 2.9 to 4.5 mg/kg (dry wt.) and exceeded 10 ng/L in the watershed's acidic streams. An ongoing study with the N.J. Department of Environmental Protection indicates that atmospheric deposition of Hg to the wetlands and streams may be augmented by substantial contributions of Hg from ground water. Although background levels of Hg in water from the underlying aquifer typically are less than 10 ng/L, concentrations in water from more than 600 domestic wells in southern New Jersey have been shown to exceed the drinking-water maximum contaminant level of 2,000 ng/L. Therefore, to determine ground-water inputs to the streams, samples of ground water discharging to the tributaries and mainstem as well as streamwater samples collected during various flow conditions were analyzed for total Hg and methylmercury (MeHg). Total Hg concentrations in ground water discharging to the tributaries and mainstem were low to moderate (0.29-22 ng/L) in relatively undeveloped areas (including wetlands), but higher (36 and 177 ng/L) in two urban/suburban areas where much of the Hg was in particulate form. In recent and ongoing studies, total Hg concentrations in unfiltered samples of surface water, except those for one suburban tributary, have ranged from 2.13 to 37.7 ng/L. Concentrations in the suburban tributary have ranged from 50 ng/L during a dry period to 250 ng/L during a wet period. Hg concentrations in samples from a wetlands-embedded reach of the mainstem varied markedly with flow. In addition to increases in concentrations of total Hg, UV absorbance and concentrations of dissolved organic carbon also increased with flow after rain events, whereas pH and concentrations of dissolved oxygen and nitrate decreased. These flow-related changes apparently result from inputs of water that has percolated through acidic, reducing wetlands soils. The biogeochemical environment of these soils, on the basis of hydrogen sulfide odors detected during piezometer placement, supports sulfate reduction and likely promotes methylation of Hg. MeHg concentrations were 0.48 ng/L after a rainfall in discharge from 0.8 m below the streambed at a mainstem wetlands site. Downstream, where the channel briefly emerges from wetlands, MeHg was detectable during a dry period only in the hyporheic-zone water from 0.15 m below the streambed and in ground water from a depth of 0.3 m (0.15 ng/L and 0.05 ng/L, respectively). MeHg was not detected in the ground-water samples from deeper points below the streambeds, but concentrations in surface water ranged from 0.17 to 2.88 ng/L. The concentration from a tributary surrounded by urban/suburban development was highest. MeHg concentrations in mainstem water did not always increase with streamflow; variations in antecedent hydrologic conditions in the wetlands may explain the unpredictable relation of concentration to flow. Overall, total Hg appears to be contributed to the streams by both ground water and atmospheric deposition, with methylation taking place at shallow levels in wetlands soils and stream sediments.
DE: 0461 Metals
DE: 0496 Water quality
DE: 0497 Wetlands (1890)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting