School of Environmental Studies, China University of Geosciences, Wuhan 430074, PR China; State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, PR China; Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, China University of Geosciences, Wuhan 430074, PR China.
School of Environmental Studies, China University of Geosciences, Wuhan 430074, PR China.
Sci Total Environ. 2022 Aug 25;836:155597. doi: 10.1016/j.scitotenv.2022.155597. Epub 2022 May 2.
The clay layer is a source to facilitate arsenic (As) enrichment in the aquifer. However, little is known about microbial processes in the clay layer and their roles in As mobilization in the underlying aquifer. In this study, high-throughput sequencing of full-length 16S rRNA gene and metagenomics were used to characterize the microbial composition and functional potential in a sediment borehole across the clay and sand layers in Hetao Basin, Inner Mongolia, China. Results showed the significant differences between the clay layer and underlying sand layer in the geochemistry, microbial composition and functional potential. Fermentation, Fe(III) reduction, As(V) reduction, sulfate reduction, thiosulfate disproportionation, reductive tricarboxylic acid and Wood-Ljungdahl pathway identified in sediments from the clay layer were positively correlated to the observed high levels of TOC, soluble ammonium, HPO-extractable As(III) and As(V) and HCl-extractable Fe(II). Although the microbial compositions of the clay and sand layers were different, the microbial functional potential at the interface between the clay and sand layers was similar with the characteristics of fermentation, ammonification and As(V) reduction. The similarity of microbial functional potential at the interface may be attributable to the interaction between the sand and adjacent clay layer with the fluctuation of groundwater level. These metabolic products from the microbial processes in the clay layers and interface would migrate into the underlying groundwater during groundwater overpumping, which facilitates As enrichment in groundwater.
粘土层是促进含水层中砷（As）富集的一个来源。然而，对于粘土层中的微生物过程及其在含水层中 As 迁移中的作用知之甚少。在这项研究中，使用全长 16S rRNA 基因高通量测序和宏基因组学来描述中国内蒙古河套盆地穿过粘土层和砂土层的沉积物钻孔中的微生物组成和功能潜力。结果表明，粘土层和下部砂层在地球化学、微生物组成和功能潜力方面存在显著差异。粘土层沉积物中鉴定出的发酵、Fe(III)还原、As(V)还原、硫酸盐还原、硫代硫酸盐歧化、还原三羧酸循环和 Wood-Ljungdahl 途径与观察到的 TOC、可溶性铵、HPO 可提取 As(III)和 As(V)和 HCl 可提取 Fe(II)的高水平呈正相关。尽管粘土层和砂土层的微生物组成不同，但粘土层和砂土层界面处的微生物功能潜力相似，具有发酵、氨化和 As(V)还原的特征。界面处微生物功能潜力的相似性可能归因于地下水水位波动时砂层与相邻粘土层之间的相互作用。这些来自粘土层和界面中微生物过程的代谢产物在地下水过度抽取期间会迁移到地下水中，从而促进地下水的砷富集。
