表生水体环境中DOM与铁氧化物可以发生广泛相互作用，该过程不仅能够影响水环境中铁的迁移形式，而且能对相关重金属的归趋产生重要影响。以往研究多注重于铁氧化物对重金属的吸附共沉淀作用，而对还原环境下不同分子量分级组分DOM与铁氧化物相互作用对重金属再迁移影响的研究却很少；并且我们的预研究表明该作用可以对铁同位素分馏产生重要影响，但分馏机理还不清楚。本项目拟以不同分子量DOM与铁氧化物混合絮体为研究对象，借助于XAFS精细结构和铁同位素分析技术，辅以元素分析、红外光谱、荧光光谱、核磁共振等研究手段，开展还原环境下不同分子量DOM与铁氧化物相互作用对重金属（砷、铅和镉）再迁移及铁同位素分馏影响的实验研究，力求从分子结构水平上揭示还原溶解过程中二者的相互作用对重金属再迁移及铁同位素分馏的制约机制。本研究的开展有助于深化认识水环境中重金属二次污染风险，并进一步丰富表生环境过程中铁同位素分馏理论。

The coprecipitation and interaction of dissolved organic matter (DOM) and Fe oxdies is common in surface and subsurface environments, which are considered to affect the speciation and transformation of iron, and concurrently the remobilization of associated toxic heavy metals. The scavenging of toxic heavy metals by iron oxides via adsorption and coprecititation were widely studied while the effect of interactions between DOM and iron oxides on the remobilization of heavy metals require a further better understanding, and this interaction may have significant influences on the iron isotope fractionation.However, its mechanisms remain unclear. Accordingly, X-ray absorption fine structure spectroscopy (XAFS) and iron isotope studies are coupled with trace metal geochemistry, IR, Fluorescence spectroscopy, NMR and so on, to better understand the interactions between DOM with different molecular weight and iron oxides, and a further study of the mechnisms of the remibilization of toxic heavy metals, including As, Pb and Cd, under anoxic environments in this project, and the induced influences on Fe isotope fractionation. This study will give a better understanding of the remobilization of heavy metals and the induced risk of contamination, and it will also provide important information for iron isotope studies in surface environments.