Researchers Find Link to Arsenic-Contaminated Groundwater

Researchers Find Link to Arsenic-Contaminated Groundwater
Human activities are not the main cause of arsenic found in groundwater in Bangladesh.
Instead, a team of researchers from Lawrence Livermore National Laboratory, Barnard College, Columbia University, University of Dhaka, Desert Research Institute, and University of Tennessee found that the arsenic in groundwater in the region is part of a natural process that predates any recent human activity, like intensive pumping.
Millions of people in Bangladesh and neighboring countries are chronically exposed to arsenic-contaminated groundwater, which causes skin lesions and increases the risk of certain cancers. Bacterial respiration of organic carbon releases naturally-occurring arsenic from sediment into groundwater, but the source of this organic carbon remains unclear.
Brian Mailloux of Barnard College and his team isolated microbial DNA from several depth intervals in arsenic-contaminated aquifers in Bangladesh and analyzed the DNA's radiocarbon signature, which reflects whether the organic carbon used by the microbes derives primarily from younger, surface-derived sources that are transported by groundwater into the aquifers, or older, sediment-derived sources.

Using "bomb pulse" radiocarbon analysis, Lawrence Livermore scientist Bruce Buchholz dated the DNA of groundwater bacteria. He found that the DNA samples were consistently younger than the sediment, suggesting that the microbes favor using surface-derived carbon.

The surface-derived carbon has flowed into the aquifer over hundreds to thousands of years—a rate that is approximately 100 times slower than groundwater flow. The results suggest that recent human activities, such as intensive groundwater pumping, have not yet significantly affected the release of arsenic into the groundwater at this site. Click to read more.

NGWA offers 15 Best Suggested Practices designed to aid groundwater professionals, including Reducing Problematic Concentrations of Arsenic in Residential Well Systems.

Arsenic in the United States
Note- Not my work - posted for my personal use.