解磷菌耦合异化铁还原诱导次生成矿对沉积物镉的固定作用及机制研究

镉是一种生物蓄积性强、毒性持久的重金属，严重威胁人类健康，沉积物镉污染治理已迫在眉睫。近年来，异化铁还原次生成矿对镉的固定受到关注，但含镉次生铁矿的生成量少且稳定性差。磷酸盐可促使异化铁还原形成更为稳定的次生矿物，然而反应机制尚不明确，且外源磷可能带来富营养化风险。因此，本项目提出利用解磷菌溶解沉积物中的难溶磷，使释放的磷酸盐诱导异化铁还原形成稳定的含Cd(II)次生矿物。项目拟研究解磷菌参与下异化铁还原次生成矿的途径，揭示次生成矿固定Cd(II)的阴离子调控机理，明确形成稳定含Cd(II)次生矿物的关键因素；研究腐殖质、铁还原菌代谢产物等电子穿梭体对胞外电子传递及镉形态的影响规律，阐明电子穿梭体对次生成矿固定Cd(II)的影响机制；进而研究沉积物修复过程中次生成矿固定Cd(II)的长期稳定性特征，实现镉的长期固定。项目可为沉积物镉污染修复提供科学依据，为保障水生态安全提供有力支撑。

Cadmium is a heavy metal with strong bioaccumulation and long-lasting toxicity, which is a serious threat to human health, thus it is extremely urgent to remediate the Cd contaminated sediments. In recent years, the immobilization of Cd via secondary mineralization induced by microbial dissimilatory iron reduction has attracted extensive attention. However, the production of Cd doped secondary iron mineral is low and the stability is poor. Phosphate can change the way of dissimilatory iron reduction and form more stable Cd doped secondary minerals. Nevertheless, the mechanism of this process remains unclear, and exogenous phosphate may have a risk of eutrophication. Consequently, this project suggests using phosphate-solubilizing bacteria (PSB) to dissolve the insoluble phosphate existed in sediments, and induce the process of dissimilatory iron reduction to form stable Cd doped secondary iron minerals. This project intends to explore approaches of secondary mineralization induced by dissimilatory iron reduction with the help of PSB, to reveal the anion control mechanism for Cd(II) fixation in secondary minerals, and to identify the key factors for the formation of stable Cd doped secondary iron minerals. This project also intends to study the influence of humus, iron-reducing bacteria metabolites and other electron shuttles on extracellular electron transport and cadmium morphology, clarify the influence mechanism of electron shuttles on Cd (II) fixing in secondary minerals. Furthermore, the stability characteristics of fixed Cd (II) in secondary minerals during sediment restoration will be studied to achieve long-term fixation of sediment cadmium. The project can provide scientific basis for the remediation of sediment Cd pollution, and provide strong theoretical support for the protection of water ecological safety.