三峡库区消落带土壤与沉积物氧化铁重结晶对重金属环境行为的影响机制

三峡库区消落带特殊的干湿交替环境，不但有利于氧化铁矿物的形态转化，还会诱导土壤理化性质发生变化导致重金属重新分配。研究表明，氧化铁重结晶能够释放或固定其负载的重金属，但目前对于氧化铁晶相重组驱动消落带土壤与沉积物中重金属再分配的机制尚不明了，由此引起的重金属迁移和形态转化是库区重金属污染控制的基础科学问题。本研究拟综合运用矿物学、地球化学分析、同步辐射等手段，从野外环境中氧化铁组成与重金属结合形态分布入手，深入研究消落带衍生氧化铁（纤铁矿）对重金属的赋存机制，并模拟实际环境（氧化-还原交替）进一步探明纤铁矿晶相重组过程及其对重金属迁移转化与赋存形态的影响机制，揭示二次成矿耦合重金属的再分配机理。研究成果将为认识三峡库区重金属的环境行为与重金属污染修复提供理论基础。

The special wet-dry alternating environment of the water-level fluctuation zones (WLFZ) in Three Gorges Reservoir area not only benefits to the transformation of iron oxides, but also changes mineral composition of the soil and leads to the redistribution of heavy metals. Recrystallization of iron oxides can release or immobilize previously-bound heavy metals. However, the mechanisms of how iron oxides transformation drives the redistribution of heavy metals in the special environment WLFZ are not clear. The transfer and morphological transformation of heavy metals are basic scientific problems in the study of heavy metal pollution control in Three Gorges Reservoir area. We will use integrated methods including geochemical analysis, mineralogical approaches and synchrotron-based X-ray absorption fine structures (XAFS). First, the composition of iron oxides and the binding form of heavy metals in the field will be studied. Second, the combining mechanism of heavy metals with lepidocrocite derived from WLFZ will be discussed. Finally, the impacts of mineral recrystallization and evolution rule of lepidocrocite on the fate and species of heavy metals under the condition of oxidation-reduction alternations will be further explored. The mechanism of secondary mineralization coupling redistribution of heavy metals will be revealed. The study will provide a theoretical basis for understanding the behavior of heavy metals and remediation of heavy metal pollution in the Three Gorges Reservoir area.