Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (3): 115-128.DOI: 10.13745/j.esf.sf.2022.1.34

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Distribution and formation processes of high fluoride groundwater in different types of aquifers in the Hualong-Xunhua Basin

XING Shiping1(), GUO Huaming1,*(), WU Ping2,*(), HU Xueda1, ZHAO Zhen2, YUAN Youjing2   

  1. 1. School of Water Resources and Environment & MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, China
    2. Key Labobratory of Geo-environment Qinghai Province, Qinghai 906 Engineering Survey and Design Institute Co., Ltd., Environmental Geological Exploration Bureau of Qinghai Province, Xining 810007, China
  • Received:2021-12-02 Revised:2022-01-12 Online:2022-05-25 Published:2022-04-28
  • Contact: GUO Huaming,WU Ping


High fluoride (F-) groundwater of natural origin is an environmental and drinking water safety issue, which has attracted worldwide attention. Although many studies have focused on the formation process of high fluoride groundwater, the distribution and formation processes of high fluoride groundwater in different types of aquifers (Quaternary aquifer, bedrock fissure or karst aquifer, clastic aquifer) under complex hydrogeological conditions in the plateau basin are poorly understood. Phreatic groundwater, confined groundwater, and spring water (Quaternary aquifer spring water and bedrock fissure spring water) samples were obtained from the Hualong-Xunhua Basin for chemical and isotopic analyses to reveal the genesis of high fluoride groundwater. The fluoride concentrations in groundwater samples were found to range from 0.25 to 7.73 mg/L. High fluoride groundwater (F->1.0 mg/L) was mainly distributed in spring water and phreatic water along the Yellow River Valley area and the Bayan low mountaineous and hilly areas, as well as in deep confined groundwater. However, the variation pattern of F- concentration along the depth is complex. Phreatic water in the Yellow River Valley area that recharged the Yellow River generally has high F- concentration, while phreatic water in the Yellow River Valley recharged by the Yellow River has low F- concentration. Ca-poor and Na-rich alkaline soda water is beneficial to F- enrichment in groundwater. Fluoride in spring water and phreatic water are mainly derived from the dissolution of fluorite. However, in confined groundwater, it is mainly derived from fluorite and other fluoride-containing minerals. For phreatic and Quaternary aquifer spring water, evaporative concentration processes promotes fluoride enrichment. In addition, competitive adsorption of coexisting anions and cation exchange are the causes of high fluoride in spring water (Quaternary aquifer spring water and bedrock fissure spring water) and phreatic water, while cation exchange contributes the most to fluoride enrichment in confined groundwater. This study provides a scientific basis for the exploration and development of safe (low fluoride) groundwater in the Hualong-Xunhua Basin.

Key words: fluoride, groundwater, the plateau basin, hydrochemical characteristics, groundwater-rock interaction

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