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Mercury Cycling in Adirondack Wetlands


Release of mercury historically deposited in wetlands of the Adirondack region, NY, USA.

Chronic historic accumulation of mercury in wetlands may delay the recovery of surface water mercury contamination in response to decreases in emissions of mercury to the atmosphere. This study quantified the amount of mercury currently retained in wetlands that is available for release to downstream aquatic environments. We found that old mercury, rather than new mercury, was released from wetland soils, and that hydrologic setting and associated wetland type influenced retention and release. Whereas mercury was consistently released from sedge dominated shallow riparian peat, mercury was not consistently released from the sphagnum dominated headwater peat. These results are likely influenced by differences in DOC character that affect decomposition, release, and transport of mercury from wetland peat to surface waters. Anthropogenic emissions of mercury into the atmosphere have increased mercury deposition and subsequently increased the contamination of surface waters and aquatic biota in remote regions. Research in the Adirondack region has shown that wetlands are important controls of total mercury (HgT) and methyl mercury (MeHg) flux to surface waters. Thus, it is possible that any effect of decreasing mercury deposition will be constrained by chronic accumulation and long-term release of mercury from wetlands.

Our research findings indicate that reductions in mercury emissions to the atmosphere may not have a large effect on the flux of mercury exported from wetlands to surface waters. Understanding the extent to which different wetland types might buffer an increase or subsequent decrease in mercury loading is critical to forecasting the recovery of mercury contaminated surface waters. Research efforts are ongoing to assess the bioavailability of the mercury released from different wetland types in the Adirondack region of New York. This research relies on interdisciplinary collaborations between graduate students and faculty in the Departments of Natural Resources and Microbiology which have been fostered by the Cornell IGERT Program in Biogeochemistry and Environmental Biocomplexity. These interdisciplinary collaborations that have brought together diverse field and laboratory expertises to address novel questions at the boundaries of our traditional disciplines would not have occurred without the framework provided by the NSF IGERT in Biogeochemistry at Cornell University.

Address Goals

1. Mercury is a significant pollutant with complex biogeochemistry. This research has led to a real improvement in our understanding of how mercury cycling within ecosystems is at least as important as gross deposition rates for determining Hg release to stream waters.

2. This will help provide a basis for educating the public about Hg contamination and the complexities involved in establishing appropriate emissions limits