HR: 11:30h
AN: NB52A-05    [Abstracts]
TI: A Mass-balance Approach to Assessing Arsenic Transport Through the Hyporheic Zone of a Mine-influenced Mountain Stream
AU: * Brown, B V
EM: bbrown25@vt.edu
AF: Virginia Tech Department of Biological Sciences, 2119 Derring Hall, Blacksburg, VA 24061 United States
AU: Valett, H M
EM: mvalett@vt.edu
AF: Virginia Tech Department of Biological Sciences, 2119 Derring Hall, Blacksburg, VA 24061 United States
AU: Schreiber, M E
EM: mschreib@vt.edu
AF: Virginia Tech Department of Geosciences, 5048 Derring Hall, Blacksburg, VA 24061 United States
AB: We are investigating the biogeochemical controls on the transport of arsenic through the hyporheic zone (i.e., zone of interaction between surface and groundwater) in a montane headwater stream in Southwest Virginia. At the site, arsenopyrite was mined from 1903 to 1919 and waste piles of roasted ore remain adjacent to the stream. Arsenic concentrations in the stream are heavily influenced by the location of the waste piles and increase exponentially with distance downstream ranging from 0.002 to over 5 mg/L. More than 90% of stream water arsenic occurs as arsenate (i.e., As(V)). We are characterizing spatial and temporal variation in arsenic fluxes using a mass-balance approach. Dilution gauging and continuous discharge measurements from flumes are being used to quantify groundwater inputs. Vertical hydraulic gradients indicate that the stream is gaining. Groundwater arsenic concentrations paired with groundwater discharge measurements are used to determine the gross groundwater load (concentration*discharge). By closing the mass-balance equation, net groundwater inputs can be compared to measured gross groundwater inputs to determine if the hyporheic zone is retaining or releasing arsenic to the stream. Employing this mass-balance approach will allow us to determine the importance of this groundwater-surface water interface in the transport of trace elements.
DE: 0400 Biogeosciences
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly