Arsenic in groundwater from Southwest Bangladesh: Sources, water quality, and potential health concern

Abstract

Arsenic (As) poisoning in groundwater has become one of the greatest environmental concerns around the world. In this study, As concentration in the groundwater samples (depth: 52–70 m) of southwestern Bangladesh was evaluated using Atomic Absorption Spectrometer (AAS) to know the current status, possible source(s), and probable health risk of As. In addition, the other relevant water quality parameters (pH, temperature, EC, TDS, Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, NO₃⁻, SO₄²⁻, HCO₃⁻, Fe, and Mn) were also measured using various instruments such as portable bench meter, Flame photometer, AAS, and Ion Chromatograph to evaluate the suitability of the water for drinking and irrigation purposes. Arsenic concentration (μg L⁻¹) ranged from 13.10 to 292 (mean ± SD: 156.9 ± 100.31), which is alarmingly, and 15 times higher than the WHO recommended value for drinking water. pH values of collected groundwater samples ranged from 7.17 to 8.09, which exhibits a lightly alkaline nature. The average abundance of major cation follows the order of Ca²⁺ > Mg²⁺ > Na⁺ > K⁺, and the average abundance of major anions follows the order of HCO₃⁻ > Cl⁻ > NO₃⁻ > SO₄²⁻, with Ca²⁺and HCO₃⁻ being the dominant cation and anion, respectively. Based on water quality assessments utilizing the water quality index and entropy water quality index, the groundwater in the region of interest was not suitable for drinking or irrigation purposes. The Piper tri-linear diagram suggests the dominant water type in the study area was the Ca-HCO₃ type, where Ca and HCO₃⁻ are the principal cations and anions, respectively. A bivariate analysis of different hydro-chemical parameters revealed that silicate weathering controls the hydrogeochemical processes in groundwater. Principal component and hierarchical cluster analysis indicate As in groundwater are geogenic in origin under reductive dissolution processes. The moderate correlation between As, Fe, and Mn indicate reductive dissolution of FeOOH and MnOOH plays a vital role in releasing As from sediment to groundwater. Probable cancer risk assessment for both adults and children revealed a higher value than the recommended value of 10⁻⁶ according to United Nations Environmental Protection Agency (USEPA), suggesting that people in the area of interest were at high carcinogenic risk.