安固里淖内陆河流域地下水硝酸盐污染时空分布特征及成因分析

Temporal and spatial distribution characteristics and origin analysis of nitrate pollution in groundwater in Angulinao inland river basin

安固里淖内陆河流域为严重缺水区,多年来,此区域的地下水研究集中水资源量及其开发方向,含水层遭受的污染受到了忽视,其中硝酸盐污染是安固里淖内陆河流域最突出的水质问题。本研究采集流域雨季前和雨季后地下水样品共258组进行全分析检测,分析流域硝酸盐分布及成因。结果表明,流域补给区水化学类型以HCO_(3)-Ca为主,阴离子类型沿流向向HCO_(3)·SO_(4)、HCO_(3)·Cl、Cl·HCO_(3)、Cl型过渡;部分地点硝酸盐超标严重,超标率达44.3%;降雨期结束后流域硝酸盐浓度升高,且污染羽沿地下水流向扩大呈条带状分布;流域地下水处于弱碱性氧化条件,适宜硝酸盐的积累。硝酸盐主要受土地利用类型影响,来源主要为农业化肥和人畜生活用水排放。

Angulinao inland river basin was a severe water shortage area,and the issues about the amount and use of groundwater resources in this area were paid much attention.However,the groundwater contamination including nitrate contamination has been neglected in this area.The present study investigated the distribution of groundwater nitrate and its factors in the Angulinao inland river basin,and 258 groundwater samples were collected for analysis.The results showed that HCO_(3)-Ca was the main hydrochemical type in the recharge area of the basin,and the anionic type was evolved with HCO_(3)·SO_(4),HCO_(3)·Cl,Cl·HCO_(3),Cl type along the groundwater flow.Nitrate concentrations in 44.3%groundwater samples in this area exceeded the standard for groundwater quality in China.The concentration of groundwater nitrate in this area increased after the rainfall period,and the pollution plume expanded along the flow direction of groundwater.The groundwater in this area characterized by weak alkaline and oxidation conditions was in favor of the enrichment of nitrate.Groundwater nitrate in this area originated mainly from agricultural fertilizer and discharge of domestic water,and the distribution of nitrate in groundwater was mainly affected by land use type.