Effect of dissolved organic matter on mercury release from water body

摘要

Dissolved organic matter (DOM) plays an important role in the process of mercury release from water body. In this study, the influence of DOM from different sources (DOM_R, DOM_S and DOM_H, extracted from rice straw, compost and humic soil respectively) on mercury reduction was investigated. The molecular weight distribution and chemical composition of DOM from each source were determined using ultrafiltration membrane technique and elemental analysis respectively. The result showed that mercury release from DOM-added samples was much lower than the control; the lowest mercury release flux was observed in the treatment of DOM_H, 25.02% of the control, followed by DOM_S and DOM_R, 62.46% and 64.95% of the control, respectively. The higher saturation degree and lower molecular weight of DOM_H was responsible for the highest inhibition degree on the mercury release. The link between DOM_H, concentration and mercury flux was also estimated and the result showed that mercury flux was increased with DOM_H at lower concentration, while decreased with DOM_H at higher concentration. Different mechanism dominated the influence of DOM on mercury release with variation of DOM concentration.