Impacts of sediment compaction on iodine enrichment in deep aquifers of the North China Plain
Impacts of sediment compaction on iodine enrichment in deep aquifers of the North China Plain
复制标题
沉积物压实对华北平原深层含水层碘富集的影响
DOI：
10.1016/j.watres.2019.05.036
复制
发表时间：
2019
期刊：
影响因子：
12.8
通讯作者：
Wang Yanxin
中科院分区：
文献类型：
--
作者：
Xue Xiaobin;Li Junxia;Xie Xianjun;Qian Kun;Wang Yanxin
为了解大规模沉积物压实对华北平原地下水碘富集的影响，对华北平原深层含水层沉积物中地下水、海水和孔隙水的水文地球化学和同位素（2 H、18 O和87 Sr/86 Sr）地球化学特征进行了研究。地下水碘浓度范围为5.8 ~ 1110 μg/L，约80%的地下水碘浓度大于100 μg/L。高碘地下水（>100 μg/L）主要分布在地面沉降严重的渤海湾地区。在几次海侵事件中沉积的沉积物被认为是地下水碘的主要来源。由粘土质沉积物压实的孔隙溶液中碘的浓度高达830 μg/L，表明海洋源碘储存在粘土质沉积物中。地下水的氢氧同位素特征表明，华北平原地下水主要由降水和强烈地面沉降引起的沉积物压实孔隙水补给。地下水和沉积物孔隙水的Cl/Br摩尔比和87 Sr/86 Sr特征进一步表明了与溶解释放的孔隙溶液混合对高碘地下水水化学演化的影响。基于地下水δ 2 H、Cl浓度和87 Sr/86 Sr的双端元混合模型计算结果表明，在高碘地下水中，溶解释放的孔隙溶液贡献了约49.1-68.9%的碘，溶解释放的孔隙溶液中碘的含量在407 ~ 572 μg/L之间。因此，本研究的结果表明，粘土质沉积物的压实可能是控制NCP深层含水层中高碘地下水成因的主要水文地质过程。
To understand the effects of large-scale sediment compaction on iodine enrichment in the groundwater system of the North China Plain (NCP), hydrogeochemical and isotope (2H,18O and87Sr/86Sr) geochemical features of groundwater, seawater and pore water of the deep aquifer sediments were characterized. Groundwater iodine concentration ranged from 5.8 to 1110 μg/L and approximately 80% of groundwater samples have iodine concentration more than 100 μg/L. High iodine groundwater (>100 μg/L) is mainly distributed in the Bohai bay area where serious land subsidence occurs. The sediments deposited during several events of marine transgression are considered as the main source of groundwater iodine. The pore solution compacted from the clayey sediments has a iodine concentration up to 830 μg/L, indicating that marine source iodine was stored in the clayey layers. The hydrogen and oxygen isotope signatures of groundwater show that the groundwater from NCP is mainly recharged by precipitation and the pore water from sediment compaction due to intense land subsidence. The Cl/Br molar ratio and87Sr/86Sr signatures of groundwater and sediment pore water further suggest the effects of mixing with compaction-released pore solution on the hydrochemical evolution of high iodine groundwater. Based on groundwater δ2H, Cl concentration and87Sr/86Sr, the results of two end-members mixing model calculation indicate that the compaction-released pore solution contributes approximately 49.1–68.9% iodine to high iodine groundwater, and the iodine from compaction-released pore solution ranges between 407 and 572 μg/L. The results of this study therefore suggest that the compaction of clayey sediments can be a major hydrogeological process controlling the genesis of high iodine groundwater in deep aquifers at NCP.