[Distribution Characteristics, Sources, and Enrichment Causes of Groundwater Fluoride in the Plain Area of Barkol-Yiwu Basin].

Abstract

High fluoride （F^-） groundwater has been found in Barkol-Yiwu Basin, and a high F^- concentration will affect the health of local residents. Taking the groundwater in the plain area of Barkol-Yiwu Basin as the research object, the chemical characteristics of groundwater and the spatial distribution of F^- were analyzed using a Durov diagram and descriptive statistics method. Based on the relative importance ranking results of random forest, PMF source analysis revealed the source of F^- and combined it with the groundwater environment and hydrogeochemical effects to determine the enrichment causes of groundwater F^-. The results showed that the groundwater was mainly weakly alkaline fresh water, and the chemical types of high F^- groundwater were mainly Na type and SO₄ type. The variation range of F^- concentration in phreatic water was 0.16-2.54 mg·L^-1, with the excess rate of 18.8%, and the variation range of F^- concentration in confined groundwater was 0.23-1.25 mg·L^-1, with the excess rate of 37.5%. The overall F^- concentration in phreatic water was greater than that in confined groundwater. The high F^- groundwater was distributed in the northeast piedmont area of Barkol Lake, Kuisu Town, the western part of Santanghu Town, Dahongliuxia Township, Xialaoba Township, and Xiamaya Township of Yiwu County. The chemical composition of groundwater was affected by leaching-evaporation concentration, geological environment, and human activities, which contributed 39.1%, 31.6%, and 29.3%, respectively. The causes of F^- enrichment in groundwater mainly included leaching-evaporation concentration, mineral dissolution, and positive cation exchange. The results were important for formulating regional groundwater resources protection and management measures and improving groundwater quality in Barkol-Yiwu Basin.