The Dynamic Of Exogenous Dissolved Organic Matter And It’s Influence On The Environmental Behavior Of Heavy Metals In Soil

Dissolved organic matter can be dissolved in the water and it is a kind of organic compounds, It is the most active ingredient in the organic fertilizer,for example municipal sewage sludge and vermicompost. manure fertilization is very popular in agricultural production, which is very important for improving soil fertility, bettering soil quality, increasing crop yield and quality. The study included dynamic of exogenous DOM in the soil and exogenous DOM impact on the behavior of heavy metals in the environment. It is important for resource utilization of municipal sewage sludge and vermicompost to provide a basis.DOM used in this paper was obtained from that of utilization of municipal sewage sludge and vermicompost after special chemical treatment, and the selected materials were neutral soil and acidic soil. Applied DOM to the soil, The behavior of DOM including transportation and transformation in soils, and the effects of DOM on Heavy metals in soils was studied.Pot experiments were studied the DOM on crops (lettuce) yield, quality, heavy metals contents and the physicochemical properties of the soil after harvest crops.The main results from this paper can be described as follows:1.After the Study included molecular weight and classification, IR and fluorescence spectra map of the DOM, the results show that compared to the sludge DOM, vermicompost DOM increase the content and the proportion of small organic molecules, carboxyl and polysaccharides, resulting in more structurally stable aromatic substances, and a little of substances such as proteins and amino acids, reduce the degree of polymerization or joint of the unsaturated structure.2.When DOM entered into soils, it will be absorbed by soil colloid. The sorption and desorption of DOM in soils will reach a balance in4hours. There is great difference between the absorbing ability of two kinds of soils, and the absorbed amount of DOM is relatively high in acidic soil with more rapid speed. As the adsorption of DOM in soils is a reversible process, under certain conditions, the DOM adsorpted by soil can return to soil solution. The soils with less adsorption abilty of DOM can release less DOM into soils through desorption, while soils with stronger absorbing ability separated more easily with DOM.3.Compared to neutral soil, acidic soil has less effect to adsorption capacity and adsorption forces of heavy metals, though two kinds of DOM have same law. In the same soil, DOM has Significantly effect to reduce adsorption capacity of heavy metals (Pb,Cu,Cd) with soils. And when the two kinds of DOM have same concentration, vermicompost DOM has a more Significantly effect to reduce adsorption capacity of Pb.4.By soil column experiments, after exotic DOM leached soil, compared to control, DOM reduce more content of heavy metals(Pb,Cu,Cr) in soil, and vermicompost DOM has a more significant effect. But, DOM has hardly effect to content of heavy metals(Cd,Zn), Cd and Zn hardly migrated to the lower soil with the exotic DOM. Though DOM has effect to content of heavy metals(Ni), there are no difference between sewage sludge DOM and vermicompost DOM.5.The growth of crops was greatly affected by DOM since the heavy metals were activated by DOM in soils contaminated by heavy metals, which resulted in toxic effects of crops:yield reduction, higher concentration of heavy metals in plant tissues and crops quality degradation. The law of the heavy metals contents (included Pb,Cu, Cr, Cd, Zn and Ni) in soil after lettuce harvest is Control> application of vermicompost DOM> Application of Sewage Sludge DOM, and corresponding to the law of the heavy metal content in the plants.When using organic fertilizer (municipal sewage sludge and vermicompost) in Farmland soils, must think over the influence of DOM, and feel one’s way.