河套平原杭锦后旗北部浅层地下水砷富集水文地质特征

Hydrogeological characteristics of arsenic enrichment in shallow groundwater in the north of Hangjinhouqi of Hetao Plain

河套平原杭锦后旗北部山前地带是黄河流域居民的主要水源地,地下水具有高砷特征,但地下水中砷的分布规律不明,给居民用水安全造成威胁。为查明该区地下水砷富集规律和成因,采集浅层地下水样品295组,沉积物样品8组,结合2孔7层水文监测钻孔和物探勘查结果,分析了河套平原杭锦后旗北部山前冲洪积倾斜平原与黄河冲湖积平原地带浅层含水系统水文地质结构、高砷地下水分布和水化学特征,探讨了地下水中砷含量分布规律和富集环境。结果表明,研究区地下水砷含量呈明显的条带状展布:横向上,从冲洪积扇顶到平原区,砷含量从<10.0μg/L升高到>400.0μg/L,沉积物颗粒逐渐变细,由氧化环境渐转变为还原环境,促进了砷的释放和富集;垂向上,富砷地下水分布在20~23、 40~50和60~70 m等3个深度范围,水化学特征显示为弱碱性还原环境,地下水化学类型以Cl·HCO_(3)-Na·Ca型为主。

The piedmont area in the north of Hangjinhouqi of Hetao Plain is the main water source for residents of the Yellow River Basin.The groundwater is characterized by high arsenic,but the distribution pattern of arse-nic is unknown,which poses a threat to water safety for the residents.In this study,295 groups of shallow groundwater samples and 8 groups of sediment samples were collected to find out the pattern and origin of arse-nic enrichment in groundwater in this area.Combined with the results of two holes and seven layers of hydrologi-cal monitoring boreholes and geophysical exploration,the hydrogeological structure,distribution and hydrochem-ical characteristics of the shallow water-bearing system in the north of the piedmountain alluvial and diluvial in-cline plain and the Yellow River alluvial plain were analyzed,and the distribution and enrichment environment of arsenic in the groundwater were discussed.The results show that the arsenic content of groundwater exhibits a clear strip-shaped distribution.Horizontally,from the top of alluvial fan to the plain area,the arsenic content increases from<10.0μg/L to>400.0μg/L,and the sediment particles gradually become finer,from oxidation environment to reduction environment,which promotes the release and enrichment of arsenic.Vertically,arse-nic-rich groundwater is distributed in three depth of 20-23 m,40-50 m and 60-70 m.The hydrochemical characteristics show that it is a weak alkali reduction environment,and the chemical type of groundwater is mainly Cl·HCO_(3)-Na·Ca.