Since health data have demonstrated that arsenic is a carcinogen, the U.S. standard for arsenic in drinking water has been lowered from 50 to 10 parts per billion, which is the same as the European Union standard, said Madeline Schreiber, assistant professor of geosciences. She and associate professor of biology Maurice Valett are lead investigators on a National Science Foundation-funded project that began in 2002 on "Transport, transformation, and retention of arsenic in a headwater stream: hyrdrologic, biological, and geochemical controls."
Research is being conducted at a site near the Virginia Tech campus, where arsenopyrite, an arsenic-bearing sulfide, was mined from 1903 to 1919. "Arsenic was used in pesticide. The extraction process involved heating the ore so that the arsenic would oxidize as a white powder," Schreiber said.
The researchers have discovered that a stream adjacent to the site is receiving arsenic from groundwater that has flowed through the mine, but that some of the arsenic is being retained in the streambed. Discovering the pathways from the mine to the stream and the conditions of discharge from groundwater into the stream are first steps to possible remediation and control, Schreiber said.
"The change that occurs as anaerobic (oxygen-free) groundwater discharges to aerobic surface water impacts the transport of arsenic. Arsenic is more mobile under anaerobic conditions, while under aerobic conditions, it is bound to iron minerals," she said "So we are asking, "What happens to arsenic as it is transported from groundwater to surface water? Is it retained at the interface between the two zones?