Effects Of Dissolvable Organic Matters On Cadmium And Zinc Adsorption By Several Soils With Different PH Values

Along with the more serious soil heavy metal pollution, adsorption of heavy metal becomes an important scientific research item in the domain of soil science and environment science in the world. Dissolvable organic matter (DOM) is the organic and inorganic pollutants' carrier in soils, and heavy metals' organic ligand. It plays a vital role in the rehabilitation of heavy metals' pollution.The effects of the three kinds of dissolvable organic matters (DOM) which were extracted from rice straw, sewage sludge and vegetable leaf on the adsorption of Cd and Zn by two soils under different temperatures were studied through the isothermal adsorption experiment. The main results were listed as follows:1. All of the adsorption data of the heavy metals could be simulated by the Langmuir equation and the correlation coefficients were above 0.95. The results showed that the binding coefficient K and maximum adsorption Xm were obviously different when the composite adsorption of Cd or Zn compared with the single adsorption without DOM. In the composite adsorption, Xm of Cd and Zn was reduced obviously than the one in the single adsorption; and the K of Cd was decreased, but the K of Zn was increased. Therefore, the binding ability of Zn was stronger than the one of Cd in the composite adsorption.2. No matter single adsorption or composite adsorption, DOM played an enhancement function to Cd and Zn in soil 1, and an antagonism function to Cd and Zn in soil 2. The effect of DOM on the two soils was different, and the scope of influence was soil 1(pH4.89) > soil 2(pH7.31). Adding rice-straw DOM to soil 1 at 20℃, in the single adsorption system, the adsorption of Cd, Zn was increased by 52.6% and 46.7% in soil 1; The adsorption of Cd and Zn was decreased by 18.2% and 9.1% in soil 2. In the composite adsorption system, the adsorption of Cd and Zn was increased by 450% and 325% in soil 1; the adsorption of Cd and Zn was decreased by 12.6% and 41.1% in soil 2. It indicated that in the composite adsorption, the enhancement function of DOM to Cd was bigger in soil 1, and the antagonism function of Zn was bigger in soil 2.3. Adding rice-straw DOM, sewage-sludge DOM and vegetable-leaf DOM to the soils at 20℃, the scope of enhancement function of DOM to Cd and Zn in soil 1 was...