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Impacts of mountaintop removal coal mining on carbon and nitrogen cycling in West Virginia headwater streams
Burke, R., K. Fritz, AND B. Johnson. Impacts of mountaintop removal coal mining on carbon and nitrogen cycling in West Virginia headwater streams. 6th Interagency Conference on Research in the Watersheds, Sheperdstown, West Virginia, July 23 - 27, 2018.
To assess the potential of MTR/VF coal mining to alter C and N cycling in receiving streams, we measured sediment denitrification enzyme activity (DEA), sediment oxygen demand (SOD) and the concentration and stable carbon isotopic composition of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in stream water during fall, winter, spring, and summer sampling campaigns conducted during 2007 and 2008.
Soil and vegetation disturbance associated with mountaintop removal and valley fill (MTR/VF) coal mining have the potential to alter carbon and nitrogen cycling in headwater streams. To assess this possibility, we measured sediment denitrification enzyme activity (DEA), sediment oxygen demand (SOD) and the concentration and stable carbon isotopic composition of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in stream water during fall, winter, spring, and summer sampling campaigns. Our measurements were conducted in 5 streams that drained nearly 100 % forested land and 5 streams that were heavily impacted by MTR/VF operations in the Twentymile Creek watershed, West Virginia (USA). We found that sediment DEA was greater and SOD lower in the MTR/VF streams than in the forested streams, but the differences were not statistically significant. We observed a weak but statistically significant correlation between DEA and SOD (r2 = 0.19, p < 0.01). Correlation of similar strength between denitrification rate and SOD has been observed by others in aquatic sediments from various freshwater and marine environments and suggests coupling between carbon cycling and denitrification. DIC concentrations and stable carbon isotopic compositions were significantly greater in the MTR/VF streams than in respective forested streams, likely reflecting enhanced carbonate weathering accompanying MTR/VF disturbance. Although the differences were not statistically significant, DOC concentrations and stable carbon isotopic compositions were slightly greater in MTR/VF than in forested streams, likely indicating mobilization of either geogenic carbon (e.g., coal) or highly weathered soil organic matter from deep in the soil profile. Given the massive disturbance to the terrestrial ecosystem caused by MTR/VF mining, the apparently modest impacts of mining on sediment DEA and SOD suggest that carbon and nitrogen cycling in these streams may be more controlled by local (i.e., riparian) organic matter inputs than by processes occurring in the watershed as a whole.
Record Details:Record Type: DOCUMENT (PRESENTATION/POSTER)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LABORATORY
SYSTEMS EXPOSURE DIVISION
ECOSYSTEM INTEGRITY BRANCH