Geochemical appraisal of groundwater arsenic contamination and human health risk assessment in the Gangetic Basin in Murshidabad District of West Bengal, India

Geogenic arsenic is a metabolic hazard to global citizens, due to its presence in most of the rocks. Natural processes such as percolation of rainwater through soil layer and water–rock interaction in weathering process principally lead to the dissolution of arsenic-bearing minerals in the aquifer system. In the present study, arsenic (As)-contaminated groundwater was analyzed covering all blocks (26 blocks) of Murshidabad District, West Bengal, India. Principally, the study focused on the assessment of groundwater quality with respect to arsenic along with other metal ions such as iron, manganese, cadmium and selenium. Tube well water samples (N = 348) were collected during pre- and post-monsoon seasons. The spatial distribution of arsenic levels ranges from 0.086 to 0.513 mg/L in pre-monsoon and 0.059–0.431 mg/L in post-monsoon, which indicates that all groundwater samples of the Murshidabad District exceeds the WHO’s permissible limit of arsenic (0.01 mg/L). Water quality index (WQI) data suggested that 5.74% and 10.3% samples are suitable for drinking purpose in the pre-monsoon and post-monsoon season, respectively. Availability of cations are as follows: Ca²⁺ > Mg²⁺ > Na⁺ > K⁺ , and anions as: SO₄²⁻ > HCO³⁻ > Cl⁻ > F⁻ > NO³⁻ in both pre-monsoon and post-monsoon seasons. Human health risk due to consumption of groundwater was assessed through USEPA designed methods as follows—hazard quotient (HQ), hazard index (HI), average daily dose of both direct ingestion of groundwater and dermal absorption of groundwater (ADDIₙgₑₛₜᵢₒₙ, ADDDₑᵣₘₐₗ ₐbₛₒᵣₚₜᵢₒₙ), and exposure frequency (EF). Thus, carcinogenic risk (CR) and non-carcinogenic risk (NCR) were determined. Results revealed that 29% and 37% of inhabitants suffered from carcinogenic and non-carcinogenic risk, respectively. On the basis of occurrence, spatial distribution and health risk assessment results of the targeted area can be marked as a moderate- to high-risk zone. The said zones need special attention for protection of public health.