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The Ecology and Management of
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Peatlands, such as the Great Dismal Swamp (GDS), can sequester large quantities of mercury from remote and point source locations. While no point sources are known for the GDS, recent evaluation of several vertebrate species reported that elevated concentrations and mercury can occur after wildfires. Little is known about coarse woody debris as a sink for mercury and the risk of remobilization during fires. Cross-sectional samples of 80-year-old Atlantic White Cedar (AWC) seed trees that blew down following salvage-logging operations in 2003 after Hurricane Isabel were collected from the Great Dismal Swamp National Wildlife Refuge. Sections were analyzed for mercury through atomic absorption spectroscopy using three sets of composited 10-year increments corresponding to 1934-1944, 1964-1974 and 1992-2002 year rings of each tree. Concentrations of mercury within each 10-year increment averaged 6.9+ 2.7 ppb, and ranged from 2.5 to 11.4 ppb. Based on the average concentration of mercury in the wood samples, a single living 65- year-old AWC tree could have as much as 2.84 mg of mercury. These results are consistent with mercury studies of live-wood samples from other species; across several deciduous species, 26% of live wood samples contained 1-2 ppb, and 11% were greater than 8 ppb. These results shed light on the history of mercury in the Great Dismal Swamp and how it is retained in AWC trees as well as the risk for mobilization during fires.
Mercury, Atlantic White Cedar, Peatlands, Great Dismal Swamp, Dendrochemistry.