Researchers tracking sources of arsenic contamination in water
Blacksburg, Va., Nov. 9, 2004 -- Virginia Tech researchers from geosciences and biology are looking at where arsenic occurs in water, how it is getting there, and how to prevent it. They will present their findings at the 116th national meeting of the Geological Society of America in Denver Nov. 7-10.
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?
The goal is to figure out how to prevent arsenic from getting into drinking water sources, she said. "We are trying to determine the biogeochemical controls on arsenic release. In this case, release was accelerated through human activity (mining). But we are also looking at how the mineral weathers; then, once it is in the water, how it interacts with the sediment and with bacteria."
Since much of the arsenic contamination is natural, rather than as a result of industry, "and a little bit goes a long way, the taxpayers will have to pay for prevention. But prevention is less expensive than remediation," she said.
The paper, "Evaluating arsenic transport within anthropogenic aquifers in mined watersheds," co-authored by Schreiber, biology associate professor Maurice Valett, biology student Brendan V. Brown of Savannah, Ga., and Craig Altare of the earth and environmental sciences department at New Mexico Tech, will be presented at 4:55 p.m. Tuesday, Nov. 9, in room 205 of the Colorado Convention Center.
Three students are working on the research project now. Two students have graduated, so two undergraduates are being added, thanks to a supplement NSF grant to support undergraduate researchers (REU).
© 2005 The Geological Society of America