A photo of Professor Brian Mailloux sitting at a desk wearing a green sweater


On February 20, 2024, Brian Mailloux, professor of environmental science and Co-Chair of the Environmental Science Department, along with colleagues from the Lamont Doherty Earth Observatory of Columbia University and Quaid-i-Azam University, in Pakistan will publish new research in Science of The Total Environment, titled  "Elevated arsenic concentrations in groundwater of the Upper Indus Plain of Pakistan across a range of redox conditions.” As part of this study, Mailloux was able to help his colleagues explore the causes of elevated arsenic (As) concentrations in the groundwater of the Ravi River floodplain, which lies on either side of the Pakistan-India border. The colleagues from Pakistan tested over 20,000 wells for arsenic, drilled 14 floodplain sites, and compared clay, sand, and silt samples from each. The Higher Education Commission (HEC) of Pakistan supported Nisbah Mushtaq in visiting Barnard and Columbia which made it possible to analyze a subset of the samples to quality control the study.  

The data revealed that levels of arsenic in the groundwater throughout this region may become disproportionately elevated due to either reductive dissolution of iron (Fe) oxides, evaporative concentration, or alkali desorption. In the Ravi River floodplain, they observed that the spatial heterogeneity in groundwater arsenic concentrations seemed linked to variations in the arsenic concentrations of aquifer sand samples taken from the same area. According to the researchers, human-induced changes in hydrology in these areas are one potential way to limit variations in groundwater arsenic levels. They assert that with more testing and targeted drilling, spatial heterogeneity could help lower arsenic exposure near the Pakistan-India border.