Hydrogeochemical characterization of groundwater with a focus on Hofmeister ions and water quality status in CKDu endemic and CKDu non‒endemic areas, Sri Lanka.

Hydro-geochemistry of drinking water was characterized in chronic kidney disease of unknown etiology (CKDu) endemic areas in Girandurukotte (GK) and Dehiattakandiya (DH) and non-endemic areas in GK, DH, and Sewanagala (SW) in Sri Lanka to comprehend any potential risk factors for CKDu. Groundwater (n = 142) and surface water (n = 08) were sampled during wet and dry seasons and analyzed for major anions, cations and stable isotopes of hydrogen and oxygen (δH and δO). Besides the typical water quality analysis, the water quality status was determined using the weighted arithmetic water quality index (WQI) and Hofmeister ion exposure levels. The measured average groundwater F level was higher than the permissible level assigned by regulatory agencies for tropical countries at CKDu locations in GK, DH and non-CKDu locations in DH and SW. Significant differences in the content of total hardness (p = 0.017) and total dissolved solids (p = 0.003) were observed between CKDu and non-CKDu locations whereas the differences were insignificant for F (p = 0.985) and alkalinity (p = 0.203). Weathering of silicate and carbonate minerals was found to be the main governing factor of groundwater compositions in both CKDu and non-CKDu areas, while recharging of groundwater is mainly determined by the rainfall than the surface water inputs. Higher ionic strength of groundwater in non-CKDu areas suggested that the potential environmental CKDu risk factors might be suppressed from dissolution into groundwater. The WQI calculations revealed that the both CKDu and non-CKDu locations were frequently presented with poor water quality. This study highlights the water quality status of the CKDu and non-CKDu locations and signifies the potential health risks that could arise even in non-CKDu areas due to the consumption of poor quality water. Accordingly, regular monitoring of water quality and assessment of Hofmeister ions exposure from food and beverages are highly warranted.