Arsenic hydrogeochemistry, quality assessment, and associated health risks of groundwater through the novel water pollution index (WPI) and GIS approach

Abstract

A total of 60 groundwater samples from an arsenic endemic region (Fukra union of Gopalganj district, Bangladesh) were collected during the premonsoon (PRM) and postmonsoon (POM) season in 2016 and were assessed for arsenic quantification along with other physico-chemical parameters such as EC, pH, TDS, total Fe, major anions, cations, and the health hazards associated with them. Anions content was found in the order of HCO3‾(419.7 mg/L)»Cl‾(23.8 mg/L)>SO42−(20.2 mg/L)>NO3‾(9.95 mg/L)>F‾(0.43 mg/L) and cations in the order of Ca2⁺(76.4 mg/L)>Mg2⁺(28 mg/L)>Na⁺(14 mg/L)>K (4.7 mg/L). Arsenic concentration ranged from BDL to 0.18 mg/L, with 90% of samples exhibiting concentration above the WHO permissible limit (0.01 mg/L). The average concentration of Total Fe was 0.14 mg/L considering both seasons. Mean ± SD values of the water quality index (WQI) and water pollution index (WPI) were 78.15 ± 30.67 and 0.81 ± 0.2, respectively. Groundwater quality was unsafe for drinking purposes in 30% of places in terms of WQI and WPI. Human health risk associated with groundwater consumption was assessed through the total hazard index (THI). The mean THI values were 11.32 and 5.45 in PRM and POM, respectively, indicating a greater chance of non-carcinogenic threat to the inhabitants as the final score is much greater than the acceptable limit of 1. GIS distribution maps of THI indicated a severe threat to both children's and adults' health. Principal component analysis (PCA) and hydrogeochemical characterization of groundwater through the Piper diagram and Gibb's plot indicated that Ca–HCO3-rich water and its reaction with arsenic-bearing sediment minerals was the main governing factor for groundwater As-enrichment in groundwater. The study will deliver an outline for a better understanding and management of groundwater quality and arsenic-induced health hazards.