西藏羊八井高温地热水砷和氟浓度及来源探析  

Concentrations and Sources of Arsenic and Fluoride in High-Temperature Geothermal Water from Yangbajing,Xizang

作　　者：许耿 肖方景 崔小梅 布多[1] 张强英[1] XU Geng;XIAO Fangjing;CUI Xiaomei;BU Duo;ZHANG Qiangying(College of Ecological Environment,Tibet University,Lhasa 850000,China)

机构地区：[1]西藏大学生态环境学院,西藏拉萨850000

出　　处：《岩矿测试》2024年第3期487-500,共14页Rock and Mineral Analysis

基　　金：国家自然科学基金项目(22266032);第二次青藏高原综合科学考察研究项目(2019QZKK0603);西藏自治区科技厅中央引导地方科技发展资金项目(XZ202202YD0016C);中央支持地方高校改革发展计划项目([2023]1号)。

摘　　要：砷(As)和氟(F)是西藏羊八井高温地热流体中两种典型的高浓度有害元素,通过地热开发可以进一步促进与加速地热源As和F向地表或近地表环境释放,导致地表水和土壤环境污染。如何从As和F浓度分布特征联系水化学特征从而揭示水体As和F的富集规律,对丰富和认识西藏地区水环境中As和F的环境地球化学行为具有重要意义。本文结合野外调查现场测定了水体常规理化指标,包括水温、pH值、电导率(EC)、总溶解固体(TDS)和盐度(SAL),采用原子荧光光谱法和X射线荧光光谱法分别测定水体和土壤样品中的As浓度,离子选择性电极法测定水体和土壤样品中的F浓度,评价As和F超标风险,探析其富集机制。结果表明:水化学类型为Na-HCO_(3)∙Cl型,水体Na+浓度高达445.5mg/L,Ca^(2+)浓度低至3.31mg/L,水体pH在7.87~9.42之间,富钠贫钙高pH是羊八井地热水和温泉水最主要的水化学特征。受水汽蒸发浓缩影响,温泉水As和F浓度高于地热水,两元素浓度最高分别达6.50mg/L和17.89mg/L。地热废水的不当处理存在水体和土壤As和F暴露风险,地热水和温泉水As和F浓度显著高于《地热资源评价方法》(DZ40—85)对有害成分规定的最高允许排放浓度(总砷为0.50mg/L,氟化物为10mg/L)。而土壤中总As浓度为79.50~99.08mg/kg,F浓度为1162.70~1285.10mg/kg,显著高于西藏土壤背景值。地热水体和地表土壤As和F富集主要为水-岩浸溶相互作用,独特的水化学特征为水体As和F浸取溶出提供了有利条件。Arsenic(As)and fluoride(F)are two typical harmful elements with high concentrations in Yangbajing high-temperature geothermal water,and the release of As and F from geothermal sources to the surface or near-surface environment can be further promoted and accelerated through geothermal development,causing surface water and soil environmental pollution.To understand the enrichment mechanism of As and F in the geothermal water body,hydrochemical characteristics as well as the concentrations of As and F were investigated by water quality analyzer,atomic fluorescence spectrometry,X-ray fluorescence spectrometry,and ion selective electrode method.The results indicate that the main sources of As and F in geothermal water and surface soil are water-rock leaching interaction.Unique hydrochemical characteristics(Na-HCO_(3)∙Cl)with high concentration Na+(reach to 445.5mg/L),poor in Ca^(2+)(as low as 3.31mg/L),and high pH(7.87−9.42)provided a favourable condition for the leaching of As and F in water.Affected by water vapor evaporation,the concentrations of As and F in hot spring water were higher than those in geothermal water and reached 6.50mg/L and 17.89mg/L,respectively.Notably,the total concentrations of As and F in waters were significantly higher than the maximum allowable emission concentrations for harmful components(0.5mg/L for As,and 10mg/L for F)in the Geothermal Resources Assessment Method(DZ40—85).Moreover,the concentrations of total As and F in the soils were 79.50−99.08mg/kg and 1162.70−1285.10mg/kg,respectively,significantly higher than the background values in Xizang soil.

关 键 词：羊八井地热水 砷 氟 原子荧光光谱法 X射线荧光光谱法 水-岩相互作用 

分 类 号：P618.64[天文地球—矿床学] P641.12[天文地球—地质学]