摘要
文章以青海贵德盆地为研究区,在分析研究区水文地质条件基础上,采集21组水样,进行了常规化学组分、砷及氢氧同位素的分析。结果表明:(1)高砷低温地热水的水温由于受到中生代印支期花岗岩岩浆余热通过基底隐伏断裂供给的影响,达到16.3～68.5℃,远高于盆地多年平均气温,其砷含量在10.4～35.4μg/L,主要赋存于新近系贵德群承压自流水中;(2)盆地高砷地热水的pH较高,均大于8.2,氧化还原电位显示负值,为还原环境,水化学类型复杂,占主导的阳离子是(Na++K+)和Ca2+,阴离子是HCO3-;(3)高砷地热水δ18O和δD的范围分别为-10.90‰～-12.32‰和-70.1‰～-84.4‰,氘盈余(d)值为12.78‰～15.02‰,说明主要接受大气降水补给;(4)相较于内蒙河套平原高砷地下水和云南腾冲地区高砷高温地下水,贵德盆地高砷低温地热水也赋存于碱性还原环境,但TDS较低,水化学类型不同,这与当地的地质背景有关;(5)盆地的地热异常不仅促进了地下水中砷水平和垂直迁移,与高温伴生的偏碱性的还原环境也加剧了地热水中砷的释放,最终导致水中砷浓度增加。
High-arsenic geothermal groundwater with low temperature is defined as the groundwater containing arsenic of greater than 10 μg/L and having temperature of higher than mean annual temperature and less than 90℃.Since research on the high-arsenic thermal groundwater with low temperature is rare,the Guide basin in Qinghai is selected as a study area to analyze the characteristics of hydrochemistry,arsenic content and isotopic compositions of hydrogen and oxygen.Results indicate that(1) because of Mesozoic Indosinian period granite magma waste heat,the temperature in the thermal arsenic groundwater ranges from 16.3 to 68.5℃ while the content of arsenic is in the range of 10.4~35.4 μg/L;(2) the thermal arsenic groundwater is in an alkaline reductive environment and the pH is higher than 8.The hydrochemical type is complex,in which the main cations are(Na++K+) and Ca2+,and the main anion is HCO-3.(3) The values of δ18O and δD in geothermal arsenic water range from-10.90‰ to-12.32‰ and from-70.1‰ to-84.4‰,respectively,and the d-excess is in the range of 12.78‰ to 15.02‰,which means that the groundwater is mainly recharged by modern precipitation.(4) Compared to high-arsenic groundwater in the Hetao plain in Inner Mongolia and high-arsenic geothermal groundwater in Tengchong in Yunnan,this high-arsenic thermal groundwater of low-temperature is also in a reducing environment,but with low TDS and the different hydrochemistry characteristics,which is be attributed to the different geological backgrounds.(5) The geothermal anomaly not only promotes the horizontal and vertical migration of arsenic in groundwater,the reduction of alkaline environment with the high temperature also promotes the release of arsenic in groundwater,eventually leading to the increase in concentration of arsenic in water.
出处
《水文地质工程地质》
CAS
CSCD
北大核心
2013年第4期121-126,共6页
Hydrogeology & Engineering Geology
基金
国家自然科学基金资助项目(40872157,40830748)
国家重点基础研究发展规划(973项目)(2010CB428802)
高等学校博士学科点专项科研基金(20110145110003)
国家高技术研究发展计划(863计划)(2012AA062602)
国家水体污染控制与治理科技重大专项(2012ZX07204-003-004)
中央高校基本科研业务费专项基金(CUGL100501)
关键词
贵德盆地
高砷低温地热水
水化学特征
Guide basin
arsenic geothermal water of low-temperature
hydrochemistry characteristics
