敦煌盆地地下水水化学特征及水质评价

Hydrochemical Characteristics and Water Quality Assessment of Groundwater in the Dunhuang Basin,Northwestern China

通过对敦煌盆地38个地下水样品的采集和测试,运用描述性统计法和因子分析法对地下水的化学特征及其成因进行了分析。在此基础上,利用美国农业部(USDA)评价方法和Wilcox图解法对地下水质进行了评价。研究结果表明:敦煌盆地浅层地下水中主要阳离子为Ca^(2+)、Na^+、Mg^(2+),主要阴离子从补给区→径流区→排泄区由HCO_3^-→SO_4^(2-)→Cl^-转换;深层地下水中阳离子以Na^+、Mg^(2+)为主,阴离子主要为Cl^-、SO_4^(2-)、HCO_3^-,且三者含量较为接近;影响盆地内地下水化学特征的主要因素为蒸发浓缩作用和矿物的溶解作用;水质评价结果显示,可作为农作物灌溉用水的水样约占总水样的26.3%,分布在党河洪积扇扇顶补给区、扇中与扇缘径流区和盆地东南部细土平原径流区。

The hydrochemical characteristics and the controlling factors of the groundwater in Dunhuang Basin were identified with descriptive statistics method and factor analysis method.United States Department of Agriculture method（USDA）and Wilcox classification diagram method were further employed to assess irrigation quality of local groundwater.The results show that the dominant cations in the shallow groundwater are Ca^（2＋）,Na^＋,Mg^（2＋）,while the dominant anions change from HCO_3^- in the recharge zone to SO_4^（2-）in the flow-through zone,and further to Cl-in the discharge zone.Deep groundwater samples are mainly dominated by Na^＋,Mg^（2＋）for cations,and Cl^-,SO_4^（2-）,HCO_3^-for anions.Evapotranspiration significantly affects the hydrogeochemical evolution of groundwater along the flow path.Groundwater irrigation quality assessment indicates that 26.3% groundwater samples are suitable for irrigation,which are distributed in the Danghe alluvial fan apex,the Danghe alluvial fan middle and edge,and the fine soil plain in southeastern Dunhuang Basin.