Effect of paddy soil components on adsorption and desorption of copper by microaggregates in paddy soil from the Mingshan watershed

Typical paddy soil,collected from the Mingshan River,was used to investigate the effect of paddy soil components on adsorption and desorption of copper by microaggregates in the soil.Simulation and incubation tests were used along with selective dissolution.The results showed that whether or not the paddy soil components were removed,the sorption of Cu2+ by the bulk soil and microaggregates fit well to the Langmuir isotherm model.The Cu2+ capacity was in the order:0.002mm2.000～0.250 mmbulk soil 0.053～0.002 mm0.250～0.053 mm for different size soil particles.The Cu2+ adsorption capacity of bulk soil and microaggregates decreased after removal of soil components,especially after removal of organic matter,up to 44.50% 2.77% in the 0.002 mm and 37.68% 3.11% in the 0.250～0.053 mm sizes.The decrease of Cu2+ adsorption by bulk soil and microaggregates after removal of soil components occurred in the order:removing organic matterremoving free iron oxideremoving amorphous iron oxide.The bulk soil and microaggregates capability to buffer the Cu2+ pollution was decreased with the decrease of specific adsorption after removal of soil components,suggesting the importance of soil components in the specific adsorption.Simultaneously,the non-specific adsorption was increased.