Newswise — Researchers from the Chinese Academy of Environmental Sciences study We assess the effects of environmental factors and microbial communities on arsenic (As) mobilization.The findings were published in Volume 15 of the journal Environmental Science and Ecotechnology, revealing important insights into the biogeochemical processes involved in As release. This study focused on processes such as desorption, reduction, complexation and co-precipitation that affect the behavior of As in the environment. Interactions between Fe (hydro)oxides and organic matter (OM), especially dissolved organic matter (DOM), were identified as a key control mechanism. OM was characterized using the fluorescence index and showed sustained biological activity throughout the experimental period. Microbial community analysis revealed the presence of bacteria capable of reducing Fe, Mn and As and those involved in metabolic transformation using EOM. When bioreactive and chemically reactive OMs were introduced, a reducing environment was formed that facilitated the release of As, Fe, and Mn, especially at high OM concentrations. Glucose and sodium lactate, which are readily metabolized by microorganisms, resulted in more release than the OM-free control group. Addition of humic acid (HA), a chemically reactive OM, had a small effect on As, but a large effect on the release of Fe and Mn. In this study, we also observed the formation of secondary iron minerals such as siderite and mackinawite, which uptake As and contribute to the reduction of As, Fe and Mn concentrations in the aqueous phase. Microbial degradation altered the properties of DOM, leading to the production of amino acids and the presence of polysaccharides, as indicated by specific functional groups. In addition, this study used canonical correspondence analysis (CCA) and redundancy analysis (RDA) to examine the relationship between environmental factors, microbial communities and As mobilization. A positive correlation was found between As(III), Fe, and Mn, and a negative correlation was observed for oxidation-reduction potential (ORP). Several bacterial genera associated with As metabolism were identified, highlighting their role in the release process.

highlight

– Groundwater arsenic migration regulated by exogenous organic matter (EOM) was demonstrated.

・Reactivity of Fe(hydr)oxide and SO_Four²⁻ As a reduction control groundwater level.

• The secondary risk of anthropogenic EOM to groundwater As and Mn releases is noteworthy.

This study significantly advances our understanding of the complex factors affecting arsenic (As) release and sheds light on the microbial processes involved in arsenic mobilization in aquatic environments. This finding has important implications for the management and mitigation of groundwater contamination caused by EOM seepage. Certain locations such as landfills, petrochemical sites and controlled aquifer recharge projects have been identified as particularly susceptible to contamination. Further investigation is required to investigate the influence of hydrodynamic and hydrogeochemical environments in practical applications. These findings highlight the need for comprehensive strategies to effectively control and mitigate environmental risks associated with EOM infiltration, aimed at protecting groundwater quality.