Impacts of External Organic Carbon on Arsenic Release in Aquifer of Jianghan Plain, Central China

This study investigated the effects of organic carbon, e.g., glucose, humic acid, and fulvic acid, on the As enrichment of groundwater from an As-bearing aquifer under the Jianghan Plain, China. Sediments were obtained by drilling samples and cultured in the laboratory by adding exotic organic matter. On the basis of high-throughput sequencing, it can be found that the addition of organic matter causes the change of microbial community diversity in the sediments. We found the co-occurrence of organic carbon and indigenous microfloral assemblage (family Clostridiaceae) promoted the transfer of As to a liquid phase by dissolving and destroying Fe oxides. Through XPS, XRD, and EXAFS analyses of sediments in different periods, we can conclude that, in this process, As was converted into labile and unstable intermediates (As2S3, As2S5, or AsS) through the degradation of organic carbon. These novel results provide valuable information for the remediation and risk control of As-contaminated sites.