Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (2): 526-538.DOI: 10.13745/j.esf.sf.2022.9.10

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Geochemical characteristics of aquifer sediments and their influence on fluoride enrichment in groundwater in the Hualong-Xunhua basin

XING Shiping1(), WU Ping2,*(), HU Xueda1, GUO Huaming1,*(), 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 Lab 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:2022-08-20 Revised:2022-09-26 Online:2023-03-25 Published:2023-01-05
  • Contact: WU Ping,GUO Huaming

Abstract:

Natural occurrence of high-fluoride groundwater in arid and semi-arid areas seriously threatens the safety of drinking water. The chemical characteristics and formation processes of high-fluoride groundwater have been well studied, but the characteristics of high-fluoride aquifer sediments and their influence on the enrichment of groundwater fluoride remain unclear. This paper investigated the hydrogeochemical characteristics of high fluoride groundwater and the elemental compositions and water-soluble components of high-fluoride aquifer sediments to reveal how sediment geochemical characteristics affect fluoride enrichment in groundwater in the Yellow River Valley of the Hualong-Xunhua basin. The results showed that groundwater fluoride concentrations ranged from 0.51 to 3.78 mg/L (average 1.38 mg/L) and tended to increase with depth. Na+ was the major cation in the high fluoride groundwater and positively correlated with F-. Total fluoride contents of sediments ranged from 460 to 1030 mg/kg, and water-soluble F- contents ranged from 0.53 to 19.9 mg/kg. In groundwater at below fluorite saturation, a positive correlation between F- and Ca2+ indicates that fluorite continues to dissolve and provides F- to groundwater, and positive correlations between F- and Si and F- and Al illustrate that weathering of fluoride-containing silicate also promotes fluoride enrichment in groundwater. Positive correlations between F- and pH, F- and HCO 3 -, and F- and Na+/Ca2+ in both water-soluble extract of sediment and groundwater indicate that desorption and cation exchange are important hydrogeochemical processes in the formation of high-fluoride groundwater. Positive correlations between water-soluble F- and total Fe/Mn in sediments suggest that desorbed F- originated from Fe/Mn oxide-bound fluoride. Additionally, groundwater salinity had a positive impact on fluoride enrichment in groundwater. The results of this study are of great significance for revealing the genetic mechanisms of high fluoride groundwater.

Key words: Hualong-Xunhua basin, high fluoride groundwater, sediments, geochemical characteristics, water-rock interaction

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