Legacy impacts of coal combusion residues in freshwater ecosystems in North Carolina
Coal combustion residuals (CCRs) released by permitted effluent streams partition to sediments and sediment pore waters where they accumulate to enriched levels in organisms at the base of the food chain. The objectives of this study were (1) to measure CCR uptake, trophic transfer, and toxicity in freshwater biota; (2) to identify CCR-specific signatures in receiving aquatic ecosystems; and (3) to measure Se in selected tissues of resident centrarchid fishes and determine differences in fish collected from CCR-impacted and reference sites as well as whether differences can be measured across sites belonging to different trophic statuses. Surface waters, sediment pore waters, three species of fish, and plankton were collected from six lakes in North Carolina; three lakes are CCR-impacted lakes due to their current or historical status as receiving waters for coal-fired power plant effluent streams and three lakes serve as reference lakes matched to each of the impacted-lakes on the basis of geographic proximity and trophic status. The research methods employed during this study include field collection of surface water, sediment pore water, and adult fish, contaminant analysis by ICP-MS and LA-ICP-MS, developmental toxicity assays, and fish feeding and breeding assays. While this study is ongoing, research results to date show that CCR contaminant signals are detectable in receiving freshwater reservoirs that both continue to and no longer receive effluent streams from associated coal-fired power plants. Contaminants including Se, As, Mn, Zn, Cu, and Sr are expected to persist in these systems for several years due to their continually elevated levels in surface waters, sediment pore waters, or fish tissues as measured in this study. Lake characteristics including surface area, depth, trophic status, and hydrological connectivity are important considerations because of their influence on contaminant retention. The results of this study suggest that ongoing monitoring of CCR receiving waters after effluent stream termination will be necessary to determine the duration of ecosystem impacts. Regular fish tissue monitoring of selenium will be especially useful for understanding persistence of selenium as a CCR contaminant in different aquatic ecosystems.
