Spatial distribution of groundwater fluoride and iron in a semi-arid region in Eastern India and human health risk assessment by Monte Carlo simulation
摘要
Groundwater quality of Banshihari Block under Dinajpur (South) District in West Bengal (India) was assessed, succeeded by evaluation of non-carcinogenic health risks linked to fluoride (F−) and iron (Fe). Groundwater samples were collected from forty-six (46) sites over the entire block in pre-monsoon season (2021). The samples emerged as safe for drinking in terms of total hardness, Mg2+, Ca2+, Na+, K+, HCO3−, Cl−, NO3−, SO42−, but except for F− (39.1% samples exceeded prescribed acceptable level of WHO) and Fe (54.3% exceeded prescribed acceptable level of BIS). Samples complied with irrigation water criteria vis a vis Sodium Adsorption Ratio (SAR), Soluble Sodium Percentage (SSP), %Na, Magnesium Ratio (MR), Residual Sodium Carbonate (RSC) and Kelly’s index (KI). Chemical weathering is instrumental for dissolution of minerals into groundwater as revealed by geochemical assessment tools and correlation analysis. Hydrochemical facies revealed that water samples are primarily of Ca-Na-HCO3, Ca-HCO3, and Na-HCO3 types. Three principal factors influenced water quality to the extents of 37.4, 14 and 10.1%, as revealed by PCA. Non-carcinogenic health hazard posed by F−and Fe were more than unity in majority of locations in the order of Total hazard index (THI)children >THI infant>THI adult. Uncertainty analysis by Monte Carlo simulation revealed that highest risk posed to children were 2.91 (F−) and 0.22 (Fe) (95th percentile), respectively. As per the sensitivity analysis undertaken with 5000 trials in Monte Carlo simulation, concentration (Ci) of F− and Fe, ingestion rate (IR) and duration of exposure emerged as major limiting factors in posing non-carcinogenic risk.