[Dynamics of dissolved organic matter in terrestrial ecosystem and its environmental impact]

Dissolved organic matter (DOM), the most active organic carbon pool in terrestrial ecosystem, has a greater effect on the mobilization, translocation, and ecological toxicity of many inorganic and organic pollutants in environment. The DOM concentration in farmlands varies from 10 to 80 mgC.L-1, while most of wetlands contain 25-50 mgC.L-1 of DOM, which is similar to the leachate from forest soils. However, soil DOM can be increased to above 200-1000 mgC.L-1 in the rhizosphere or in the plots amended with organic manures. Generally, soil DOM containing a great deal of lower molecular weight fractions or hydrophilic fractions is more mobile and readily biodegradable, compared to the DOM with larger molecular weight or hydrophobic fractions. However, soils with lower pH and higher amount of oxides can adsorb DOM more strongly, and as a result, the mobile DOM in the soils will be reduced. Liming, water-logging, dry-wet recycling and higher temperature can increase the concentration of soil DOM. Furthermore, DOM can enhance the dissolution and translocation of inorganic and organic pollutants, due to the formation of DOM-pollutant complex, resulting in environmental risks. It was suggested that the dynamics of DOM in terrestrial ecosystem and the transportation flux and model of DOM or its associated pollutants from terrestrial to aquatic ecosystem should be considered in future research.