Dynamics Of Dissolved Organic Matter And Its Impact On The Behaviors Of Copper And Cadmium In Farmland

Dissolved organic matter (DOM), an important active organic carbon pool in terrestrial ecosystem, plays a role in the mobilization, translocation, and toxicity of many inorganic and organic pollutants in environment. Now, researches on dissolved organic matters have been increasing in terrestrial ecosystem. In this paper, we selected several organic matters, such as green manure, pig manure, sewage sludge and pig manure compost, and their extracts to investigate the dynamics of DOM and its effects on the environmental behaviors of heavy metals (copper and cadmium) in soils through labortory study, pot and field micro-plot trials.The dynamics of dissolved organic matter (DOM) and the environmental behavior of associated Cu in Cu-contaminated acidic and calcareous soils amended with green manure (Vicia faba L.), pig manure and sewage sludge by pot experiment with ryegrass were studied to explore organic wastes-derived DOM effect on soil Cu dissolution and bioavailability. As compared to control treatments without the addition of organic wastes, in the initial phase the concentration of DOM in the organic wastes-treated soils was increased drastically by 0.4- to 7.5-folds, depending on organic wastes origins. The green manure treated soils exhibited the highest DOM level followed by the pig manure amended soil. However, DOM concentration in the treated soils reduced markedly as time elapse due to DOM biodegradation, especially in the first one week after the organic wastes application with the decomposition rate of 65% for the green manure treated soil DOM, 37.8% for pig manure DOM and 27% for sewage sludge DOM. It was found that DOM enhanced greatly Cu dissolution in two Cu-contaminated soils amended with green manure and pig manure. In the initial application phase for green manure and pig manure water soluble Cu concentration were 3.6-5 times and 0.6 times higher in the treated soils than that in the control, respectively. The soluble Cu concentration was reduced with the decrease of DOM in the soils, exhibiting an obvious positive linear correlation. However, the soluble Cu concentration differences between the sewage sludge-treated soil and the control were not...