Grantee Research Project Results
2001 Progress Report: Chemical and Biological Control of Mercury Cycling in Upland, Wetland and Lake Ecosystems in the Northeastern U.S.
EPA Grant Number: R827633Title: Chemical and Biological Control of Mercury Cycling in Upland, Wetland and Lake Ecosystems in the Northeastern U.S.
Investigators: Driscoll, Charles T. , Yavitt, Joseph , Newton, Robert , Munson, Ronald
Institution: Syracuse University
Current Institution: Syracuse University , Cornell University , Smith College , Tetra Tech Inc.
EPA Project Officer: Packard, Benjamin H
Project Period: November 1, 1999 through October 31, 2002 (Extended to October 31, 2003)
Project Period Covered by this Report: November 1, 2000 through October 31, 2001
Project Amount: $786,680
RFA: Mercury: Transport and Fate through a Watershed (1999) RFA Text | Recipients Lists
Research Category: Watersheds , Heavy Metal Contamination of Soil/Water , Water , Safer Chemicals
Objective:
The objectives of this research project are to:(1) quantify patterns of transport and transformations of mercury species in an upland northern hardwood forest through adjacent wetlands to the aquatic environment; (2) evaluate the processes and mechanisms controlling methyl mercury concentrations and transport in pore waters and surface waters in wetlands; (3) evaluate historical patterns of mercury dynamics in soft-water lakes; and (4) develop and apply a lake/watershed mercury cycling model to a lake/watershed ecosystem.Progress Summary:
There is considerable interest in understanding controls on mercury (Hg) inputs to remote lake/watershed ecosystems. In this regard, a detailed study is being conducted on the biogeochemistry of Hg at Sunday Pond (41? 51' N, 75? 06' W), a forested wetland/lake/watershed in the Adirondack region of New York. Sunday Pond is a drainage lake with a maximum depth of 5.5 m, an average depth of 2.5 m and a surface area of 7.7 ha. The Sunday Pond watershed surface area is 1,340 ha and comprised of approximately 75 percent deciduous forest and about 15 percent deciduous-coniferous mixed forest. The soils in the watershed are predominantly Spodosols that were derived from glacial till. Wetlands comprise about 21 percent of the watershed, largely conifer swamps, riparian wetlands, and beaver impoundments. The long-term annual precipitation for the site is 120 cm. Annual discharge for the study period is about 86 cm.The lake/watershed was instrumented for the study of the biogeochemistry of Hg in 1999. Wet deposition, total Hg, and methyl Hg are being monitored at Huntington Forest through the Mercury Deposition Network (MDN). The Huntington Forest is approximately 75 km from Sunday Pond and the site is a National Atmospheric Deposition Program (NADP) site. At Sunday Pond watershed, two upland plots were established for intensive study, one in a deciduous stand and the other in a coniferous stand. Replicate soil samples were collected for major horizons (Oa, E, Bh, Bs1, Bs2) in each stand. These stands were instrumented with replicate throughfall collectors, litter collectors, and zero-tension Teflon lysimeters installed beneath the forest floor, Bh horizon, and within the Bs horizon. Piezometers were established in upland forests, in peat deposits adjacent to the pond, and in riparian wetlands for the collection of ground waters. Nine surface water sampling stations have been established. Seven of these sites are located in the watershed that drains into Sunday Pond. Sites also were established at the deep water station and outlet of Sunday Pond. Drainage water samples were collected at approximately monthly intervals. Stream gauging stations were established at the major inlet to Sunday Pond and the outlet.
Wet Hg deposition was 10.8 µg/m2-yr, with 0.6 percent occurring as methyl Hg. Concentrations and wet deposition of total Hg and methyl Hg for the Adirondacks are similar to values reported for other sites in eastern North America. Coniferous throughfall concentration and fluxes were enriched in total Hg in comparison to wet deposition. In contrast, the deciduous canopy was a sink for wet Hg deposition. At both sites, throughfall was enriched in methyl Hg in comparison with wet deposition. Litterfall measurements showed that this was an important pathway of inputs of total Hg and methyl Hg to the forest floor. Soil concentrations of total Hg were highest in the Oa horizon (13-189 ng/g). Concentrations were low in the E horizon (3.9-25.2 ng/g), higher in the Bh horizon (3.7-67.5 ng/g), and lower in the lower mineral soil (2.7-47.5 ng/g). This pattern of total Hg with soil depth is similar to the horizon deposition of organic matter. In contrast to total Hg, concentrations of methyl Hg were uniform with soil depth. Concentrations and fluxes of total Hg were elevated in forest floor leachate, with values decreasing in mineral soil solutions. Concentrations of total Hg in soil solutions were strongly correlated with concentrations of dissolved organic carbon (DOC). This pattern also indicates that the deposition of total Hg in Spodosols is closely coupled with the deposition of organic carbon. Concentrations of methyl Hg were considerably lower in soil solutions than in throughfall, suggesting that upland soils are net sinks for inputs of methyl Hg. Concentrations of total and methyl Hg in ground waters draining uplands were similar to values observed in the lower mineral soil solutions. Concentrations of total and methyl Hg in peat pore waters were highly variable. The hydraulic conductivity of peat sites was low, and these wetlands are not an important source of total and methyl Hg to surface waters. In contrast, concentrations of total and methyl Hg were high in riparian pore waters. It appears that these sites are important in the supply of methyl Hg to surface waters.
Concentrations of Hg in surface waters ranged from 1.9 to 4.6 ng/L, with methyl Hg concentrations from 0.2 to 2.53 ng/L. Drainage water concentrations of total Hg seem to be related to concentrations of DOC. About 79 percent of wet Hg deposition is retained in the watershed. Sunday Pond is a sink for inputs of total Hg; about 15 percent of the total Hg entering the lake was retained in lake sediments. The watershed, particularly riparian wetlands, and the lake are sources of methyl Hg to downstream surface waters. A sediment core was collected for the lake and dated using 210Pb. The historical Hg deposition showed an increase around 1900 with values peaking near 1980 at 2.5-3.5 times above background values. Sediment deposition of Hg has decreased over the last 20 years. The mass balance of Hg for the lake was in good agreement with the estimate Hg burial from measurements of sediment deposition. The Hg biogeochemistry data are being used to calibrate the Mercury in Adirondack Wetlands Lakes and Terrestrial Systems (MAWLTS) model for the site.
Future Activities:
We plan to continue the measurements of Hg species in riparian gound waters and at surface water sites. Process-level studies on Hg dynamics in wetlands will continue. We also will continue to use the MAWLTS model to test hypotheses concerning Hg cycling in northern upland/wetland/lake ecosystems.Journal Articles:
No journal articles submitted with this report: View all 28 publications for this projectSupplemental Keywords:
soil, water, mercury, watershed, wetlands, lakes, Adirondacks., RFA, Scientific Discipline, Geographic Area, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, Hydrology, Contaminated Sediments, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, Chemistry, State, Fate & Transport, Ecological Effects - Environmental Exposure & Risk, Air Deposition, Mercury, fate and transport, ecological exposure, aquatic, wetland ecosystem, forested watersheds, contaminated sediment, upland ecosystems, surface water, mercury cycling, mercury cycle, watershed influences, dissolved organic carbon, water acidification, Clean Air Act, lake sediment, lake ecosystem, wetland, atmospheric deposition, heavy metals, lake ecosystemsRelevant Websites:
http://www.science.smith.edu/departments/Geology/mercury/ Exit Synthesis Report of Research from EPA’s Science to Achieve Results (STAR) Grant Program: Mercury Transport and Fate Through a Watershed (PDF) (42 pp, 760 K)
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.