Zhang Hengxing, Zhang Yilong, Wu Lijie, Wang Wenzhong, Li Xiaohan
Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shijiazhuang, 050061, China.
Key Laboratory of Groundwater Science and Engineering, Ministry of Natural Resources, Shijiazhuang, 050061, China.
Environ Sci Pollut Res Int. 2023 May;30(22):63305-63321. doi: 10.1007/s11356-023-26448-w. Epub 2023 Mar 24.
The alluvial-lacustrine strata that were formed by the evolution of rivers and lakes in the Hetao Plain during the Late Quaternary have an important influence on the formation and distribution of shallow high-arsenic groundwater. This study analyzed the distribution characteristics and depositional environments of shallow high-arsenic groundwater in study area using 1179 groundwater samples and more than 1100 pieces of drilling data. The indicator kriging statistics and the study results of the Quaternary lithofacies paleogeography show that the study area can be divided into three high-arsenic probabilistic distribution areas, namely, the Houtao Plain (HTP), the Yellow River Channel Belt (YRCB), and the Eastern Hubao Plain (EHBP). The depositional environment of the HTP was shaped by the alluviation of the Yellow River during the Late Pleistocene-Holocene. The YRCB is still affected by the alluviation of the Yellow River presently, and the EHBP was almost unaffected by the Yellow River. The high-arsenic groundwater in the EHBP is mostly distributed in the relatively continuous alluvial-lacustrine strata and has a typical hydrochemical type of HCO, with the highest Meq(HCO/SO) and the highest reduction degree of SO. By contrast, the high-arsenic groundwater in the alluvial-lacustrine environments of the HTP and the YRCB accounts for only 14.77% and 20.13%, respectively, and has only less than 40% of HCO dominant type water. The high-arsenic groundwater in these two areas is generally located in the alluvial or alternating fluvial-lacustrine strata. However, the two areas exist more than three alluvial-lacustrine layers with a thickness of over 2 m each, which play a critical role in the formation of high-arsenic groundwater. Moreover, affected by alluvial aquifers in the same system, the high-arsenic groundwater in both the HTP and the YRCB is not intensively distributed and does not represent a typical HCO dominant type. The S produced by the massive reduction of SO might co-precipitate with Fe and As, which may explain why the EHBP has lower arsenic concentration than the HTP and the YRCB, both of which have a lower reduction degree of SO.
晚第四纪期间，河套平原河流与湖泊演化形成的冲湖积地层，对浅层高砷地下水的形成与分布具有重要影响。本研究利用1179个地下水样品和1100余件钻孔资料，分析了研究区浅层高砷地下水的分布特征与沉积环境。指示克里金统计及第四纪岩相古地理研究结果表明，研究区可分为三个高砷概率分布区，即后套平原（HTP）、黄河河道带（YRCB）和东部呼包平原（EHBP）。HTP的沉积环境是由晚更新世—全新世期间黄河冲积作用形成的。YRCB目前仍受黄河冲积作用影响，而EHBP几乎未受黄河影响。EHBP的高砷地下水大多分布在相对连续的冲湖积地层中，具有典型的HCO水化学类型，Meq（HCO/SO）最高，SO还原程度最高。相比之下，HTP和YRCB冲湖积环境中的高砷地下水分别仅占14.77%和20.13%，HCO优势型水占比均不到40%。这两个区域的高砷地下水一般位于冲积或河流—湖泊交替地层中。然而，这两个区域存在三个以上厚度均超过2米的冲湖积层，它们对高砷地下水的形成起着关键作用。此外，受同一系统冲积含水层的影响，HTP和YRCB的高砷地下水分布并不集中，也不代表典型的HCO优势型。SO大量还原产生的S可能与Fe和As共沉淀，这或许可以解释为什么EHBP的砷浓度低于HTP和YRCB，而后两者的SO还原程度较低。
