Mercury concentrations in pond fish in relation to a coal-fired power plant

Many studies have reported that atmospheric mercury is the primary cause for bioaccumulation in fish from remote lakes. Few data, however, are available on the possible effects of near-field mercury deposition on mercury concentrations in fish from local waters. Mercury concentrations were surveyed in fish from 23 ponds in the vicinity of a 543-megawatt coal-fired power plant located at Dickerson, Maryland. A stratified random sampling design was used to select ponds within zones delineated by concentric arcs mapped at 3, 7, 10, and 15 km from the plant. For each pond, mercury concentrations were measured by atomic absorption spectrometry in sunfish (bluegill or green sunfish) in all ponds, and largemouth bass, which were present in 14 of the ponds. Mean mercury concentrations in the ponds ranged from 0.01 to 0.38 ppm for sunfish and 0.04 to 0.43 ppm for bass. Stepwise multiple regression identified variables related to tissue concentrations. Differences between strata were tested with analysis of covariance, after adjusting the concentrations to account for differences in water quality. The observed pattern of mercury bioaccumulation did not match the pattern predicted by a wet deposition model.