BAMS project

BAMS: Brinton Arsenic Mine Study

TRANSPORT, TRANSFORMATION, AND RETENTION OF ARSENIC IN A HEADWATER STREAM: HYDROLOGIC, BIOLOGICAL, AND GEOCHEMICAL CONTROLS

Madeline Schreiber and H. Maurice Valett
Dept. Geological Sciences and Dept. Biology, Virginia Tech
Link to Dr. Schreiber Link to arsenic project with Dr. Schreiber

On October 31, 2001, the U.S. EPA announced that the drinking water standard for arsenic will be lowered from 50 to 10 mg/L, due to the carcinogenic and toxic effects of arsenic on humans. It is well-known that arsenic is readily transported in natural waters and that its form, speciation, and concentration are affected by biogeochemical reactions. In this proposal, we address the hydrologic, geochemical and biological controls on the mobility of arsenic in a low-order stream-aquifer system impacted by past mining activities. Preliminary findings from the study site have led PIs Schreiber and Valett to pose the following questions:

· What factors control spatial and temporal variations in arsenic fluxes to the stream? What is the extent of the capture
zone of the stream? How does this change seasonally?
· How do hyporheic processes influence retention of arsenic in the stream?
· In what solid phases is arsenic present in sediment? How does solid phase arsenic concentration vary with redox conditions?
· How do metabolic processes in the stream alter the speciation and concentration of arsenic? How do arsenic concentrations change rates of organic matter processing? How does metabolic variation translate to differential arsenic processing?

How do we plan to do this? Scroll down.

To address these questions, we utilize a combination of field, laboratory, and modeling techniques in four research elements to evaluate the controls on arsenic mobility within the stream, with specific emphasis on characterizing the role of the hyporheic zone in acting as a source or a sink for arsenic. The proposed research elements include employing hydrologic and geochemical monitoring to characterize groundwater and surface water end-members as well as to describe biogeochemical conditions within the hyporheic zone. In addition, transient storage models will be used to evaluate the hydrologic characteristics of the hyporheic zone and, through incorporation of reactive uptake terms, to address the role of the hyporheic zone in retarding or promoting arsenic transport to the stream. Finally, experimental techniques will be utilized to assess the importance of sediment-water interaction, biotic impacts on arsenic, and alteration of ecosystem processes due to elevated arsenic concentrations.

Results of this proposed research will have implications for our general understanding of the biogeochemical cycling of redox-sensitive trace elements such as arsenic. The tightening of the arsenic drinking water standard will drive federal and state agencies to closely examine sources of both natural and human-introduced arsenic contamination. Improving the knowledge of the processes that control arsenic mobility will greatly aid these agencies in developing plans for protecting and treating drinking water supplies.