新疆车尔臣河流域绿洲带地下水咸化与污染主控因素

Controlling Factors of Groundwater Salinization and Pollution in the Oasis Zone of the Cherchen River Basin of Xinjiang

车尔臣河流域绿洲带地下水是当地居民生产生活的重要水源,查明地下水咸化和污染的控制因素,对可持续开发利用地下水资源和保护沙漠绿洲带生态环境具有重要意义.在该区共采集36组单一结构潜水样品和54组多层结构潜水-承压水样品,在确定地下水主要离子分布特征和污染现状基础上,应用水文地球化学方法(Piper图、多元统计、Gibbs模型和离子间内联关系)综合揭示地下水咸化和污染的主控因素.研究区地下水从山前倾斜平原单一结构潜水至冲洪积平原多层结构潜水-承压水具有一定分带性,Cl-Na水(87.8%)是研究区地下水主要的水化学类型.单一结构潜水水质明显优于多层结构潜水-承压水,多层结构潜水-承压水咸化主要由Na^(+)(均值9969 mg·L^(-1))、Cl^(-)(均值13687 mg·L^(-1))和SO_(4)^(2-)(均值5840 mg·L^(-1))导致,自然的水文地球化学过程是导致地下水水质恶化的主要原因.地下水化学主要受水岩作用和蒸发-浓缩作用控制,硅酸盐岩和蒸发盐岩矿物溶解是地下水化学组分的重要来源,而强烈的蒸发盐岩溶解过程对冲洪积平原区多层结构潜水-承压水的控制程度更高,加之在蒸发-浓缩和阳离子交换作用共同影响下,冲洪积平原区多层结构潜水-承压水咸化现象更为严重.此外,农田集中区农业施肥对地下水NO_(3)^(-)产生一定影响.

Groundwater is a vital resource for local human life and production in the oasis zone of the Cherchen River Basin of Xinjiang.Understanding the controlling factors of groundwater salinization and pollution is of great significance for the sustainable utilization of groundwater resources and protection of the ecological environment in desert oasis areas.In light of this,a total of 36 single structure unconfined groundwater samples and 54 multi-layered structure unconfined and confined groundwater samples were collected from the oasis zone of the Cherchen River Basin and evaluated for the distribution characteristics and pollution status of major ions.Hydrogeochemical methods(e.g.,Piper diagram,multivariate statistics,Gibbs model,and relationships among ions)were used to determine the main controlling factors of groundwater salinization and pollution.Differences in hydrogeochemical zonation were found from the single structure unconfined aquifers in sloping plains of piedmont areas to the multi-layered structure unconfined and confined aquifers in alluvial-proluvial plain areas,and Cl-Na(87.8%)was the main hydrochemical type in the groundwater of the study area.The quality of single structure unconfined groundwater was starkly better than that of the multi-layered unconfined and confined groundwater,which was mainly caused by Na^(+)(mean value of 9969 mg·L^(-1)),Cl^(-)(13687 mg·L^(-1)),and SO_(4)^(2-)(5840 mg·L^(-1)).Moreover,the natural hydrogeochemical process was the main reason for the deterioration of groundwater quality.The hydrochemistry was mainly controlled by the water-rock interaction and evaporation processes.The mineral dissolution of silicates and evaporites was an important source of chemical ions in the groundwater.Furthermore,the chemical weathering of evaporites combined with the processes of evaporation and cation exchange had a significant influence on the salinization of multi-layered unconfined and confined groundwater in alluvial-proluvial plain areas.In addition,synthetic fertilizers were the main pollution sources of NO_(3)^(-) in groundwater in the intensive agricultural zones.