Non-carcinogenic health risk assessment with source identification of nitrate and fluoride polluted groundwater of Wardha sub-basin, central India

In order to understand the pollution status of groundwater with geochemical evolution and appraisal of its probable public health risk due to nitrate (NO3-) and fluoride (F-), a total of 93 groundwater samples were collected during pre-monsoon (May) period from Wardha sub-basin, central India. By employing Piper plot, transition from Ca-HCO3 type water (recharge waters) to Na-Cl (saline water) type water through mixed Ca-Na-HCO3, mixed Ca-Mg-Cl (reverse ion exchange waters) and Ca-Cl types (leachate waters), were observed. The Geogenic processes such as silicate, dolomite, halite and carbonate weathering along with calcite precipitation and ion exchange process were identified as major controlling factors for evolution and alteration of groundwater chemistry. The Saturation index highlighted that the groundwater in the area is oversaturated with respect to the mineral calcite and dolomite, and under saturated with gypsum, fluorite and halite. The high NO3- and F- concentration overpassing the permissible limit were found in 54.8% and 18.5% of samples. The plot of F- with Na+/Ca2+, Na+/Mg2+ and F-/Cl- established fluoride bearing rock weathering is responsible for F- contamination. Based on the cluster analysis, the groundwater was grouped into Cluster-I Ca-Na-HCO3 type (61.3%) and Cluster-II Na-Ca-HCO3-Cl type (30.1%). The total hazard index (HI) based on human health risk assessment (HHRA) model for cumulative NO3- and F- toxicity through oral and dermal pathways were computed as 100%, 97.85% and 96.77% for children, female and male populations respectively. The HQ((nitrate)) > 1 through ingestion pathway were in 84.95%, 68.82% and 62.37%, and HQ((fluoride)) > 1 in 83.87%, 62.37% and 43.01% of the groundwater samples were recorded for children, female and male population respectively. The risk assessment study highlighted very high toxicity and severe health impact of ingestion of contaminated groundwater on public health.