Compartmentalization of mercury in biotic components of terrestrial flood plain ecosystems adjacent to the South River AT Waynesboro, VA
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Aquatic Hg contamination extending more than 200 km along the South River, South Fork of the Shenandoah River, and Shenandoah River in western VA has been recognized since 1977. Flooding has transported considerable Hg onto the flood plain resulting in highly variable terrestrial soil contamination. At our Waynesboro, VA, old field and forest research sites, this is characteristically 5 to 25 μg Hg g−1 with individual samples containing more than twice that level. Upstream control site soils have concentrations <1 μg Hg g−1. Producer and consumer trophic levels were sampled during the summer growing seasons between 1983 and 1985, and analyzed for the presence of Hg. Widespread distribution throughout the ecosystem was observed. Acid washed roots of eight tree and two vine species contained up to 2.9 μg Hg g−1dw and those of one of the 14 herbaceous species sampled, Allium canadense, contained >4 μg Hg g−1dw. Lower concentration levels were found in leaves. A moss and 13 fungi were also associated with significant tissue Hg concentrations. Distribution within the animal community includes its presence in three macroinvertebrates (eg. earthworms with 10–16 μg Hg g−1dw total tissue Hg) and several microinvertebrate arthropods. Hg was also found in various tissues of three small mammals, Microtus, Peromyscus, and Blarina (eg. kidney concentrations up to ≈30 μg Hg g−1dw). These data support the hypothesis that Hg residues in river sediments are not sequestered from adjacent terrestrial biotic communities and are an available pool for the extension of bioaccumulation wherever flooding occurs. The concentrations of Hg in these flood plain ecosystems are great enough to invite further investigation.
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