RESUMO
This paper presents the groundwater quality assessment of the upper Brahmaputra floodplains of Assam on a seasonal basis. A total of 88 samples were analyzed for the presence of potentially toxic elements in two seasons. In addition, an attempt is made to identify any possible associated health risks to the residents via the drinking water pathway. The study reveals the presence of various potentially toxic elements, in particular, manganese, iron, nickel, and fluoride concentration exceeding the drinking water specifications set by BIS and WHO drinking water standards. The degree of groundwater contamination was assessed using the Water Quality Index, Heavy metal Pollution Index, Heavy metal Evaluation Index, and Degree of Contamination. The spatial distribution maps of groundwater quality were prepared using geographical information system. The non-carcinogenic health risk was evaluated using hazard quotients and hazard index as per the United States Environmental Protection Agency methodology. The hazard quotient of fluoride and manganese have values > 1, which exceeds USEPA recommended benchmark. The health risk assessment identified that the risk was highest during the pre-monsoon season, and the child population is more vulnerable to non-carcinogenic risk than the adults. Findings of cancer risk identified that pre-monsoon groundwater samples from the Golaghat District pose the highest health risks in the upper Brahmaputra floodplains. The risk is highest in the southwest of the study area, followed by the south and then by the north.