Effects of peat and water quality parameters on groundwater arsenic contamination in Bangladesh



To clarify the effect of peat and groundwater quality parameters on groundwater arsenic (As) contamination, As concentrations and the source of nitrogen (N) in groundwater and peat, and oxidation-reduction potential (ORP) and ammonium-N concentration of groundwater were compared between As-contaminated and uncontaminated areas in Bangladesh. Groundwater in the contaminated area had a reducing ORP with a high ammonium-N concentration, whereas groundwater in the uncontaminated area had a non-reducing ORP with a low ammonium-N concentration. Peat was present only in the contaminated area, whose As concentration was very high, indicating the critical role of peat in groundwater As contamination. The source of N in peat and groundwater was identified as chemical N fertilizer. N present in peat and groundwater served as a nutrient, enhancing microbial activity. In the reducing ORP condition, As was thought to be released intensively to groundwater by the mechanism of reductive release.