Effect of Low Molecular Weight Organic Carboxylic Acids on Adsorption of Copper by Variable Charge Soils

Effect of low molecular weight organic carboxylic acids on adsorption of copper by variable charge soils was investigated using indoor experiment method. The results showed that the effect was related to the kind of organic acids and the type of soils. The adsorption of copper increased significantly with increased citric acid and malic acid, while the adsorption of copper increased with oxalic acid in lower concentration and decreased with oxalic acid in higher concentration. The increased adsorption of copper by organic acids mainly attributed to the formation of soil- organic acid- cation ternary surface complexes. The copper adsorbed in this manner could not be desorbed by NaNO3, which may reduce the mobility of copper in the soil and the availability of copper to plants.