ABSTRACT
Mercury burdens in sediments and other nonbiological materials are estimated to have increased up to five times prehuman levels, primarily as a result of anthropogenic activities (USNAS, 1978). Maximum increases are reported in freshwater and estuarine sediments and in freshwater lakes and rivers, but estimated increases in oceanic waters and terrestrial soils have been negligible (USNAS, 1978). Methylmercury accounts for a comparatively small fraction of the total mercury found in sediments, surface waters, and sediment interstitial waters of Poplar Creek, Tennessee, which was initially contaminated with mercury in the 1950s and 1960s. Mercury measurements in Poplar Creek from 1993 to 1994 showed that methylmercury accounted for 0.01% of the total mercury in sediments, 0.1% in surface waters, and 0.3% in sediment interstitial waters (Campbell et al., 1998). The residence time of mercury in nonbiological materials is variable, and depends on a number of physicochemical conditions. Estimated half-time residence values for mercury are 11 days in the atmosphere, 1000 years in terrestrial soils, 2100 to 3200 years in ocean waters, and more than 250 million years in oceanic sediments (USNAS, 1978; Boudou and Ribeyre, 1983; Clarkson et al., 1984); however, this estimate was only 1 month to 5 years for water from the contaminated Saguenay River in Quebec (Smith and Loring, 1981).
