Co-occurrence, sources and co-enrichment mechanism of arsenic, fluoride in groundwater from Huaihe River Basin, China

Abstract

Arsenic (As), fluoride (F−) are both ubiquitous in groundwater, and co-exposure to these elements through contaminated drinking water may cause detrimental effects on human health more in comparison with individual exposure. As, F− co-occurrence in groundwater of the inland plain in Huaihe River Basin, China is a major concern, where inhabitants are rely on groundwater as the leading water source for drinking to date. This work employs an approach of hydrochemical analysis and modelling to identify the possible origin of As and F−, to analyze co-enrichment mechanism, and to estimate the associated exposure risk. The results shows presence of elevated As and F− concentrations is an important factor affecting groundwater quality from 62 groundwater samples. The recorded As concentrations vary from 0.23 to 20.40 μg/L, with a mean of 5.95 μg/L, F− concentrations vary from 0.54 to 2.60 μg/L, with a mean of 1.29 mg/L, and 8 % of samples are simultaneously above their permissible limits in drinking water by the WHO. Groundwater with As, F− co-contamination is occurred within reducing and alkaline aquifers, and its chemical type is HCO3–Na. The hydrochemical processes involved in the co-contamination are reductive desorption, evaporation, and ion exchange, which are controlled by local geology, geomorphology, and hydrochemistry. Groundwater As is derived and released by reductive desorption and F− is mainly originated by fluorite dissolution. Groundwater As, F− are geogenic sources, and the mechanisms for co-contamination are associated with high elemental abundance, flat terrain, alkaline and reductive groundwater conditions. The research provides a case study about groundwater As, F− co-contamination, which may be enhance understanding the co-enrichment mechanism in semi-humid areas.