Analysis of high-fluoride groundwater formation mechanisms and assessment of health risk in Baxia region, Zhangjiakou

Abstract

Totally, 391 unconfined groundwater samples(depth ≤ 100 m) were collected in order to investigate the high-fluoride groundwater formation causes, and explore the potential impacts on drinking water safety to local residents in Baxia region, Zhangjiakou.Hydrochemical analysis, graphical method, ions ratio method and saturation index calculation method were applied in this study to analyze the spatial distribution and formation mechanisms of high-F- groundwater.Meanwhile, the non-carcinogenic human health risk assessment model recommended by US EPA was also used to evaluate health risk of four groups of receptors.The results indicate that high-F- groundwater(F->1.5 mg/L) mainly distribute in the low-lying and piedmont zone of the downstream of high-F- magmatic rock, enclosed basin, runoff stagnant area along the river and other areas.The dissolution and precipitation of the minerals, crystal lattice replacement under alkaline environment, ion exchange are the major mechanisms for high-F- groundwater formation in the study area.Salt effect can affect F- enrichment in groundwater, but it is not the principal mechanism.There is no correlation between agricultural activities and F- enrichment in groundwater.Additionally, the power plants, steelworks and other factories distributed in Baxia region are the potential pollution sources of the Yongding River system.The impacts of these industrial contamination sources on high-F- groundwater formation cannot be ignored.The hazard index values of infants, children, adult males and adult females were 1.20, 0.74, 0.69 and 0.56, respectively, demonstrating the younger people are more susceptible to fluoride contamination.Moreover, the adult females are more resistant to fluoride contamination than the adult males in the study area.Thus, it is suggested to develop the multi-source combined water supply mode for high risk areas and improve the efficiency of defluorination, in order to ensure water supply safety.

Keywords

• high-fluoride groundwater
• water-rock interaction
• ion exchange
• health risk
• baxia region