除草剂草萘胺在土壤中的降解与吸附行为

Degradation and Adsorption Behavior of Napropamide in Soils

采用色谱学（HPLC和GC-MS）和光谱学（UV和FT-IR）方法研究了除草剂草萘胺在3种土壤（黑土、砖红壤和黄棕壤）中的降解和吸附行为,并对草萘胺土壤中降解的影响因素、降解产物和吸附机理进行了分析.结果表明,在本实验条件下,草萘胺降解速率随土壤温度（15-35℃）和有机质含量（r=0.979 4）增加而加快;灭菌条件下的半衰期约是未灭菌时的3倍,土壤微生物是影响草萘胺在土壤中降解的主要因素;草萘胺在黄棕壤中的降解途径可能是脱烷基,降解产物可能为N-甲基-2-（1-萘氧基）丙酰胺和N-乙基-2-（1-萘氧基）丙酰胺.草萘胺在黄棕壤、砖红壤和黑土上的吸附系数（Kf）值分别为1.29、3.43和13.36,3种土壤上的吸附自由能（ΔG）均小于40 kJ·mol^-1,即以物理吸附为主,其吸附行为可用Freundlich模型描述.红外光谱学研究进一步证实了3种土壤对草萘胺吸附容量差异是黑土〉砖红壤〉黄棕壤.

Chromatography（HPLC and GC-MS） and spectroscopy（UV and FT-IR） methods were conducted to study the degradation and adsorption behavior of napropamide in soils.Influence factors of degradation,degradation products and adsorption mechanism were analyzed.The results showed that degradation rate of napropamide increased with enhancing temperature（15-35℃）and organic matter content in soil was the most important factor which influenced the degradation half-life of napropamide in soil,and their relative coefficient（r） reached（0.9794）.The degradation half-life of napropamide in sterilized soil was almost 3-fold of that in non-sterilized soil,and soil microorganisms were contributed to the degradation of napropamide.The probable degradation products were N-methyl-2-（1-naphthoxy）-propionamide and N-ethyl-2-（1-naphthoxy）-propionamide.The possible degradation pathways were dealkylation.Adsorption isoterms of napropamide on three soils such as Yellow-brown soil,Latersol and Black Soil could be described by Freundlich equation with the corresponding adsorption coefficient（Kf） of 1.29,3.43 and 13.36,and the adsorption free energy （ΔG） of napropamide on the three soils was less than 40kJ·mol^-1 which largely resulted from the physical adsorption involving in hydrogen-bonding,hydrophobic bonding,coordination and van der waal force.Comparison to the FT-IR spectra of the three soils,the results certificated that the sorption capacity of three soils was Black Soil〉Latersol〉Yellow-brown Soil.