Abstract
Groundwater is a critical resource in India for the supply of drinking water and for irrigation. Its usage is limited not only by its quantity but also by its quality. Among the most important contaminants of groundwater in India is arsenic, which naturally accumulates in some aquifers. In this study we create a random forest model with over 145,000 arsenic concentration measurements and over two dozen predictor variables of surface environmental parameters to produce hazard and exposure maps of the areas and populations potentially exposed to high arsenic concentrations (>10 µg/L) in groundwater. Statistical relationships found between the predictor variables and arsenic measurements are broadly consistent with major geochemical processes known to mobilize arsenic in aquifers. In addition to known high arsenic areas, such as along the Ganges and Brahmaputra rivers, we have identified several other areas around the country that have hitherto not been identified as potential arsenic hotspots. Based on recent reported rates of household groundwater use for rural and urban areas, we estimate that between about 18–30 million people in India are currently at risk of high exposure to arsenic through their drinking water supply. The hazard models here can be used to inform prioritization of groundwater quality testing and environmental public health tracking programs.
Highlights
Around the world, but so in India, there is an ever-increasing dependence on groundwater for drinking water supplies and irrigation [1,2]
The no information rate refers to the accuracy that would be achieved without a model and is the proportion of the more frequent class of the dataset, i.e., 58% of the arsenic measurement points are equal to or less than 10 μg/L
The purpose of the hazard models produced here is to offer an overview of where high concentrations of geogenic arsenic are likely to be found in groundwater across the whole of India, with some insight into the physical processes at work, as well as to assess the size of the populations potentially affected
Summary
But so in India, there is an ever-increasing dependence on groundwater for drinking water supplies and irrigation [1,2]. Its longer residence time and exposure to varying geochemical environments in an aquifer, can subject groundwater to the accumulation of various chemical elements in sufficiently high concentrations to pose a health risk to those using it for drinking or cooking [3]. Examples of such naturally occurring (geogenic) contaminants include arsenic, fluoride, manganese, and uranium. Many of the large-scale occurrences of geogenic arsenic contamination of groundwater are found in Asia and are due to the release of arsenic found in
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