Assessment of arsenic contamination in agricultural soils of Gangetic basin in Buxar, Bhojpur and Patna districts in Bihar, India

Abstract Arsenic (As) is a nonessential and toxic metalloid found in sediments, soils and aquatic environments. The contamination of As is a serious problem in South and Southeast Asia threatening the health of millions of people. In this study, 71 soil samples were collected from agricultural fields from Bihar, India situated in the middle Gangetic basin to understand the status of As contamination. The 71 samples from Bihar were taken from three districts; Buxar (n = 21), Bhojpur (n = 34) and Patna (n = 16). Arsenic concentration in soil samples was determined by the wavelength dispersive X-ray fluorescence (WD-XRF) method. The pH, oxidation reduction potential (ORP), organic matter (OM) and cation exchange capacity (CEC) of the samples were also analysed. The mean and range of As concentration were found to be 16.72 mg kg− 1 (13.9–19.4 mg kg− 1), 17.18 mg kg− 1 (13.9–21.1 mg kg− 1) and 17.16 mg kg− 1 (14.8–20.5 mg kg− 1) in Buxar, Bhojpur and Patna, respectively. Of the 71 samples from Bihar, five samples had As levels equal to or higher than the maximum permissible limit i.e. 20 mg kg− 1 for agricultural soil. These five samples were taken from the village of Salempur, Benwaliya, Gundi, Daulatpur and Katesar. To assess the contamination level, various indices like contamination factor, ecological risk assessment and geoaccumulation index were calculated, which indicated “moderate to high” As contamination in the studied areas. The study provides information about the As contamination scenario in middle Gangetic basin and proposes to conduct more comprehensive surveys to understand As contamination in the hugely populated state of Bihar.