State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, P. R. China.
Institute of Earth sciences, China University of Geosciences (Beijing), Beijing 100083, P. R. China.
Environ Sci Technol. 2022 Jul 19;56(14):10105-10119. doi: 10.1021/acs.est.2c02623. Epub 2022 Jun 27.
High-arsenic (As) groundwaters, a worldwide issue, are critically controlled by multiple interconnected biogeochemical processes. However, there is limited information on the complex biogeochemical interaction networks that cause groundwater As enrichment in aquifer systems. The western Hetao basin was selected as a study area to address this knowledge gap, offering an aquifer system where groundwater flows from an oxidizing proximal fan (low dissolved As) to a reducing flat plain (high dissolved As). The key microbial interaction networks underpinning the biogeochemical pathways responsible for As mobilization along the groundwater flow path were characterized by genome-resolved metagenomic analysis. Genes associated with microbial Fe(II) oxidation and dissimilatory nitrate reduction were noted in the proximal fan, suggesting the importance of nitrate-dependent Fe(II) oxidation in immobilizing As. However, genes catalyzing microbial Fe(III) reduction () and As(V) detoxification () were highlighted in groundwater samples downgradient flow path, inferring that reductive dissolution of As-bearing Fe(III) (oxyhydr)oxides mobilized As(V), followed by enzymatic reduction to As(III). Genes associated with ammonium oxidation ( and ) were also positively correlated with Fe(III) reduction (), suggesting a role for the Feammox process in driving As mobilization. The current study illustrates how genomic sequencing tools can help dissect complex biogeochemical systems, and strengthen biogeochemical models that capture key aspects of groundwater As enrichment.
高砷（As）地下水是一个全球性问题，受到多种相互关联的生物地球化学过程的严格控制。然而，关于导致含水层系统中地下水砷富集的复杂生物地球化学相互作用网络的信息有限。西部河套盆地被选为研究区，以解决这一知识空白，提供了一个含水层系统，地下水从氧化的近源扇（低溶解 As）流向还原的平原（高溶解 As）。通过基因组解析宏基因组分析，对沿地下水流动路径导致砷迁移的生物地球化学途径的关键微生物相互作用网络进行了表征。在近源扇中发现了与微生物 Fe(II)氧化和异化硝酸盐还原相关的基因，表明硝酸盐依赖的 Fe(II)氧化在固定 As 方面的重要性。然而，在地下水样本下游流路径中突出了催化微生物 Fe(III)还原 () 和 As(V)解毒 () 的基因，推断含砷 Fe(III)（oxyhydr）氧化物的还原溶解使 As(V)移动，然后通过酶还原为 As(III)。与铵氧化 ( 和 ) 相关的基因也与 Fe(III)还原 () 呈正相关，表明 Feammox 过程在驱动 As 迁移方面的作用。本研究说明了基因组测序工具如何帮助剖析复杂的生物地球化学系统，并增强捕获地下水砷富集关键方面的生物地球化学模型。
