RESUMO
Biodegradation is the most economical and efficient process for remediating polycyclic aromatic hydrocarbons (PAHs) such as naphthalene (Nap). Soil composition is pivotal in controlling PAH migration and transformation. Iron minerals such as siderite and magnetite are the primary components of soil and sediment and play key roles in organic pollutant biodegradation. However, it is unclear whether siderite and magnetite promote or inhibit Nap biodegradation. The effects of siderite and magnetite on Nap biodegradation were investigated through batch experiments in this study. The results indicated that siderite increased Nap biodegradation efficiency by 7.87%, whereas magnetite inhibited Nap biodegradation efficiency by 3.54%. In the presence of siderite, Nap-degrading bacteria with acid-producing effects promoted siderite dissolution via metabolic activity, resulting in an increased Fe (II) concentration in solution which accelerated the iron reduction process and promoted Nap biodegradation. In addition, the presence of iron minerals altered the genus-level community structure. Anaerobic sulfate-reducing bacteria such as Desulfosporosinus occurred in the presence of siderite, indicating that sulfate reduction occurred in advance under the influence of siderite. In the presence of magnetite, Fe (III) in iron minerals were converted to Fe (II), and under the mediation of microorganisms, Fe (II) combined with carbonate to form secondary minerals (e.g., siderite). Secondary minerals were attached to the surface of magnetite, which inhibited magnetite dissolution and reduced the efficiency of Fe (III) utilization by microorganisms. Furthermore, as the reaction proceeds, acid-producing microorganisms promoted magnetite further dissolution, resulting in a longer duration of the Fe (III) reduction process. Bacteria utilizing sulfuric acid as the terminal electron acceptor consumed organic matter more rapidly than those using iron as the terminal electron acceptor. Therefore, magnetite inhibited Nap degradation. These observations enhance our understanding of the interaction mechanisms of iron minerals, organic pollutants, and degrading bacteria during the biodegradation process.