Investigating the Impact of Dissolved Organic Carbon Sources on Arsenic Availability in Groundwater.

Arsenic contamination of groundwater is a global problem, and millions of people in Bangladesh, Cambodia, United States, Chile, Mexico, Argentina, China, India are affected by it. Routine consumption of As-contaminated water may put people at risk for arsenicosis and cancer. The release of arsenic from sediments into groundwater is controlled by microbially mediated redox processes, with both As and Fe reduction generally increasing the mobility and concentrations of As in groundwater. Organic carbon, such as dissolved organic carbon (DOC) or dissolved organic matter (DOM), generally fuels As and Fe reduction, but different carbon sources have different reactivities in the environment. Simple DOC species can directly be utilized by a large number of organisms while more complex DOM particles may require special enzymes for digestion, and thus the particular carbon source can affect the biotic mobility of As. The objective of this research is to quantify how different sources of dissolved organic carbon may impact microbially mediated arsenic release to groundwater. Lactate, acetate, humic acid, and fulvic acid having the same concentration (30mM) will be separately introduced to characterized sediment samples (10 g each) from a Cambodian Pleistocene aquifer that is at risk for As contamination. The concentration of arsenic in the sediment will be found prior to the addition of organic carbon, and the concentration of As in solution will be monitored every four days over a period of 32 days after carbon is added in order to quantify the impacts of dissolved organic carbon source on As release. The results of this investigation may be useful for gauging the potential for As contamination once the organic carbon sources in an aquifer have been determined.