甘肃敦煌地区疏勒河尾闾区地下水化学特征及成因分析

Hydrochemical characteristics and genetic mechanism analysis of groundwater in the tail area of the Shule River,Dunhuang,Gansu

疏勒河尾闾区是护卫敦煌绿洲及文化的生态安全屏障,但是对地下水化学的研究相对较少。本次研究在野外调查及采样测试的基础上,综合运用数理统计、Piper三线图、离子相关性分析、Gibbs图及离子比例系数等方法明确了疏勒河尾闾区的地下水化学特征,并对其成因进行了分析。结果表明:疏勒河尾闾区地下水水质总体呈弱碱性,具有高溶解性总固体及高硬度的特征,水化学类型主要为Cl^(-)·SO_(4)^(2-)-Na^(+)型。地下水水化学演化是由蒸发浓缩作用主导,同时风化溶解和阳离子交换共同作用的结果。地下水中的Ca^(2+)及Mg^(2+)主要来自于蒸发岩及硅酸盐的溶解,Na^(+)主要来源于岩盐溶解。高氟水的形成与片麻岩中普遍存在的黑云母矿物、蒸发浓缩主导的水文地球化学作用以及地势低洼的地形条件有关。成果不仅丰富了疏勒河流域内的地下水化学研究,亦可为敦煌绿洲生态安全屏障区的保护与建设提供科学依据。

The tail area of the Shule River is an ecological security barrier to protect Dunhuang Oasis and culture,but there is relatively little research on hydrochemical chemistry.Based on field investigation and sampling test,the hydrochemical characteristics and Genetic Mechanism of groundwater in the tail area of the Shule River were confirmed through the methods of mathematical statistics,Piper trigram,ion correlation analysis,Gibbs diagram,and ion proportion coefficient.The results show that the groundwater quality in the tail area of the Shule River is weakly alkaline,with high total dissolved solids and high hardness,and the main hydrochemical type is Cl^(-)·SO_(4)^(2-)—Na^(+).The hydrochemical evolution of groundwater is dominated by evaporation concentration,accompanied by weathering dissolution and cation exchange.Ca^(2+)and Mg^(2+)in groundwater are mainly derived from the dissolution of evaporite and silicate,and Na^(+)is dominated sourced from the dissolution of rock salt.The formation of high fluoride water is related to the widespread biotite minerals in gneiss,hydrogeochemical action dominated by evaporation and concentration,and low-lying topographic conditions.This research not only enrich the study of hydrochemical in the Shule River Basin,but also provide scientific basis for the protection and construction of the ecological security barrier of Dunhuang Oasis.