Impacts of Acid Mine Drainage on Dissolved Inorganic Carbon Cycling in Receiving Streams

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05-10954 Atekwana... Streams represent an important link in the conversion of terrestrial carbon and its transfer to the atmospheric or oceanic reservoir. Perturbation of dissolved inorganic carbon (DIC) pool in streams by acid mine drainage (AMD) has important consequences for biological activities, chemical reactions, and carbon dynamics. This project will investigate the hypothesis that AMD impacted watersheds act as a "chemical pump" converting and transferring carbon from terrestrial reservoirs to the atmospheric reservoir. Carbonate buffering reactions in AMD impacted watersheds potentially convert large amounts of carbon stored in the terrestrial reservoir into solution, which is lost to the atmosphere as acid mine drainage is discharged to streams. Given the more than 557,650 abandoned mine sites in the United States, and more globally, AMD impacted watersheds may serve as a significant source of CO2 to the atmosphere in the long term, and thus increasing the atmospheric carbon budget. Carbon cycling in AMD impacted streams will be investigated by assessing DIC flux from AMD impacted groundwater to streams, the evolution of DIC within the streams, the exchange between stream water DIC and atmospheric CO2, and export of stream water DIC from impacted watersheds. The project objectives will be achieved by conducting field and laboratory studies to: 1) document the spatial and temporal patterns of DIC, isotope ratio of DIC, major ions, and metals in AMD impacted groundwater and stream water, 2) determine the important physical and biogeochemical processes controlling the distribution, concentration, and isotope ratio of DIC in AMD impacted stream water, and 3) develop a model that captures the dynamic interaction of the processes and controls on carbon cycling in AMD impacted streams. Research on carbon cycling in AMD impacted watersheds is an important component of the larger global change question resulting from anthropogenic forcing. Thus, the proposed research is expected to provide a framework for understanding carbon fluxes in AMD impacted watersheds, which is critical for assessing anthropogenic forcing on watershed-scale carbon dynamics. This study will allow us to determine important controls on the transfer and exchange of CO2 between AMD impacted watershed and the atmosphere. As part of the broader impact components, two students (a minority graduate and an undergraduate student) will be mentored and trained in this project. Field sampling related to the proposed project will form the basis of hands-on field and laboratory exercises in aqueous geochemistry and stable isotope geology courses taught by the PI. The PI will also engage other undergraduates as part of University of Missouri Rolla (UMR) Opportunities for Undergraduate Research Experience (OURE) program. Seniors and junior high school students in the UMRs summer Jackling Institute with a geosciences preference will also be engaged in the field and laboratory component of this project. The results of the study will be disseminated at geoscience conferences and in peer review publications