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Dissolved organic matter (dissolved organic matter, DOM), also known as the water-soluble organic matter, mainly refers to can be dissolved in water, acid or alkali solution of organic matter, such as natural water, organic matter, organic matter in the soil solution, soil and organic fertilizer be water, acid or alkali leaching of organic matter. Its operation is defined as organic matter through 0.45μm membrane. Because of its water solubility characteristics, DOM is considered terrestrial ecosystems and aquatic ecosystems is an important and very active chemical component is associated with spheres pedosphere important form of exchange of substances, affecting soil formation and nutrient transport material, and organic environmental pollutants behavioral characteristics (such as toxicity, and transforming characteristics of biodegradability, etc.). As people concerned about the deepening of organic pollutants, DOM environmental behaviors of organic matter research is increasingly becoming soil science, ecology and environmental science and other disciplines of research focus. In this paper, organic materials (rice straw) as DOM sources studied its decomposition process of dynamic changes of DOM. Meanwhile, the use of completely mixed statutory quantity of DOM various stages of decomposition herbicide (Bensulfuron, BSM) and polycyclic aromatic hydrocarbons (pyrene, PYR) in the soil adsorption and desorption behavior, and explores the impact mechanism. The main conclusions are: (1) the use of chemical analysis, XAD-8 resin grouping method of decomposition of rice straw produced during the changing nature of DOM composition characteristics. The results showed that during the decomposition of organic material content of dissolution and chemical composition of DOM is a dynamic process of change. In the early stages of decomposition of organic materials, organic materials such as its water-soluble substance is eluted major source of DOM, then DOM and organic acids to carbohydrate-based composition, showed strong hydrophilicity. With the further decomposition of straw, hemicellulose, cellulose decomposition products become the main source DOM, DOM mainly composed of time molecular weight, strong aroma substances showed a strong hydrophobicity. Straw decomposition 91 days, DOC, DON, soluble sugar, soluble phenolic acids are stabilized, but DOM content of each component is still in flux. Through correlation analysis showed that different indicators certain correlation exists between where solubility and solubility of carbon phenolic acids, humic acid (HA) was significantly positively correlated with fulvic acid (FA) was significantly negatively correlated solubility sugar and hydrophilic component was positively correlated with soluble phenolic humic acid was significantly positively correlated with the hydrophobic component humic acid, fulvic acid, respectively, with the hydrophilic component was significantly positively correlated. (2) using the characteristic bands of infrared spectroscopy scanning and optical properties of DOM changes in its structure, the structure shows that with the ongoing decomposing straw, extracted DOM its ΔlogK first increased and then decreased, while A 280 values, A 254 values ??and the E 4 / E 6 increased, indicating that the degree of oxidation and aromatic DOM enhancements, aliphatic reduced molecular structure to a complex change the direction of the molecular weight increases. DOM carboxyl group, a carbonyl group and a phenolic hydroxyl content increased, a methoxy group and a hydroxyl content decreased, as acidic solution of the polymer from the base continues to generate the dark. Meanwhile, DOM extractable HA ratio (PQ) rising, FA is greater than the initial rate of formation of HA, with the incubation time, FA converted to HA. Seen from the infrared spectrum, the different stages of the DOM itself contains functional groups are similar. Include: methyl, methylene, methine, hydroxyl, carboxyl, amide group, and a benzene ring and the like; compound mainly composed of: carbohydrates, sugars, fatty acids, aromatic acids, alcohols, amide compounds and phenolic compounds. (3) BSM and PYR adsorption. Desorption exist two acts, namely rapid adsorption - desorption stage and slow adsorption - desorption stage, 8h can basically within reach adsorption - desorption equilibrium. Meanwhile, linear equations and Freundilch equation can describe BSM and PYR in soil adsorption and desorption behavior, BSM and PYR desorption hysteresis exists, desorption is not entirely reversible adsorption process, which exists between the two different mechanisms. (4) DOM addition inhibits BSM and PYR soil adsorption, but to promote the desorption of BSM and PYR. However, different stages of DOM produced inhibition and promotion effect is not the same, between the various stages of the DOM inhibition and promotion effect produced significant difference (p <0.05). Overall, DOM effect on both inhibit or promote BSM straw decomposition with the extension of time weakened; while DOM effect on PYR both inhibit or promote straw decomposition with the extension of time increased, this effect is a variety of factors the result, in which the hydrophilic component - hydrophobic component and fulvic acid humic counting an important role. Hydrophilic component and fulvic acid adsorption and desorption of BSM plays a major role, while the hydrophobic component and humic acid adsorption and desorption in PYR play a major role.
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