Waste-water impacts on groundwater: Cl/Br ratios and implications for arsenic pollution of groundwater in the Bengal Basin and Red River Basin, Vietnam

► Groundwater in the Bengal Basin is widely polluted by domestic waste-water. ► The impact on groundwater can be quantified using Cl/Br mass ratios. ► Both NO3 and SO4 in groundwater are sourced from waste-water. ► Pollution of groundwater by arsenic is decreased adjacent to sources of waste-water. ► Distally from its source, waste-water may exacerbate As-pollution of groundwater.