[Cadmium adsorption in soil influenced by dissolved organic matter derived from rice straw and sediment]

Dissolved organic matter (DOM) is an active component in territorial ecosystems. Effects of two types of DOMs extracted from sediment(DOMsed) and rice straw(DOMrs) on isotherm adsorption of Cd in latosol red soil (acidic soil), paddy soil and drab soil(alkaline soil) were studied using batch equilibrium studies. The maximum adsorption of Cd in all the 3 soils used was reduced by the additions of both of DOMsed and DOMrs. The range of the maximum adsorption of Cd decreased from 17.3% to 93.9% from all the 3 soils when DOMs were added. It was found that the decreased in the maximum adsorption of Cd was in order of latosol red soil > paddy soil > drab soil when the same DOM(DOMsed or DOMrs) was added. Effects of DOMsed or DOMrs on Cd adsorption were positively related with the soil pH. The maximum adsorption of Cd in the soils was dependent on the characteristics of soil solid when no DOM was added, and decided by the DOMs in soil solution when DOM was added. The results imply that the proposed technology using organic manure to stabilize Cd in soils is not suitable for remediation of contaminated soil.