Hydrochemical investigation of groundwater and probabilistic health risk assessment from fluoride and iron intake in a ferruginous Barind tract

Abstract

ABSTRACT Hydrochemical properties of groundwater (n = 32) collected from eight Gram Panchayats (GP) in Kushmandi Block of South Dinajpur District in West Bengal, India and human health risk posed by groundwater fluoride (F−) and iron (Fe) are reported. About 18% and 28.7% of the collected water samples exceeded the permissible limits for F− and Fe, respectively, as per prescribed potable water quality standards of WHO and Bureau of Indian Standards. Total Dissolved Solid in groundwater never exceeded the acceptable limit of 500 mg l −1 (maximum value was 301.6 mg l −1) while NO3- ranged from near zero to 17.8 mg l−1, never exceeding the safe limit of 45 mg l−1. Hydrogeochemical analyses revealed the dominance of Ca/Na-bicarbonate type water throughout the Block and indicated that fluorite (CaF2) could be the most prominent source of F− in groundwater. Non-carcinogenic health risk index due to exposure to F− was more than unity in infants, children and adults in the order of HQChildren>HQInfant>HQAdult. Sensitivity analysis to ascertain non-carcinogenic human health risk of F− through multi-exposure pathways undertaken by Monte Carlo (MC) simulation (Oracle Crystal Ball, version 11.1.2.4.850) indicated that concentration of F− and Fe (Ci), their ingestion rate (IR), and exposure duration (ED) were the most influential governing factors behind non-carcinogenic health risks posed by F− and Fe consumption. Groundwater was rated as having ‘Low’ irrigation water quality (Sodium Adsorption Ratio, SAR <10 and Residual Sodium Carbonate, RSC of 0.41–2.88). Other important parameters of irrigation water quality, such as electrical conductivity (maximum 409 μS cm−1) and chloride (maximum 30.8 mg l−1), were also well within the recommended safe limits.