Extraction and Composition of Dissolved Organic Matter in Poyang Lake and Its Effects on Morphological Changes of Heavy Metals

Dissolved organic matter (DOM) is generally thought to impact the bioavailability of heavy metals. However, the source of wetland DOM and its interaction with heavy metals remain poorly understood. Fluorescence excitation emission matrices (EEMs)-fluorescence regional integration (FRI) coupling techniques and chromophoric dissolved organic matter (CDOM) was used to explore the source of DOM of Poyang Lake including water body, soil and plants, and the effects on morphological changes of heavy metals. The results showed that the best DOM extraction effect can be obtained with the soil-water mass ratio 1:10, centrifuged at 4 000 rpm for 30 min, and the 0.45 μm glass fiber filter by orthogonal test. There were four types of peaks of DOM in water body of Poyang Lake, which was input mainly by land source, while six types of peaks (ACTDBE) were observed in soil. Soil DOM is highly humified with large molecular weight. More types of fluorescent peaks were observed in plant and the content of DOM in plants was higher than that of water body and soil due to the plant proteins. The content of fulvic acid was less than tryptophan in DOM of Triarrhena lutarioriparia and Phragmites communis in Longkou, while the opposite were in other samples. Furthermore, pot experiment illustrated that DOM had an activation effect on Cd, Cu and Zn and a passivation effect on Cr and Pb with the increase of DOM content. After the addition of exogenous DOM, Cr, Pb and Zn were immobilized by the function together with DOM and plants, while Cd and Cu were activated.