敌草胺在土壤中的吸附及其与持久性和生物有效性之间的关系

土壤吸附是农药在环境中归趋的关键支配因素，也是支配农药在环境中的持久性和生物有效性的重要因素之一。该文采用高效液相色谱法研究了除草剂敌草胺在不同性质土壤中的吸附、持久性和生物有效性以及吸附与土壤持久性、蚯蚓生物有效性之间的关系。结果表明，在供试浓度范围内，采用批量平衡技术测定的敌草胺土壤吸附等温线可用Freundlich模型表征（r>0.99），土壤有机质含量（PPt50）在61.3-97.6 d之间；微生物对敌草胺在土壤中的持久性影响显著，微生物降解是敌草胺在土壤环境中降解的主要途径，灭菌处理后其在土壤中的半衰期延长了2.09~3.65倍。蚯蚓Eisenia foetida对敌草胺的吸收和生物积累也主要取决于土壤性质，特别是土壤的有机质含量水平（Pr=-0.885，Pr=-0.796，Pt50=94.210-3.535 Kf和BAF=0.264-0.014 Kf，表明吸附系数可用作模型参数来评价敌草胺在土壤中的持久性和生物有效性。

Adsorption, persistence and bioavailability of napropamide in soil

Soil adsorption is generally recognized as a key to controlling the fate and transports of a pesticide in environment, and it also affects the persistence and bioavailability of pesticide. The present study was conducted to investigate the adsorption, persistence and bioavailability of the herbicide napropamide in soils with different properties using high-performance liquid chromatography (HPLC). Soil adsorption of napropamide was determined using the batch equilibration technique described by a Freundlich isotherm equation with correlation coefficients (r)>0.99. Regression of adsorption coefficient (K_f) against selected soil indicates that organic matter (OM) content was the most influential factor governing adsorption of napropamide (P<0.01) followed by clay content (P<0.1). Napropamide had relatively longer persistence in soil, and its degradation in soil followed the first-order kinetics with the half-lives (t₅₀) varying from 61.3 to 97.6 d, which appeared to decrease with soil OM content. The persistence of napropamide in sterilized soil was 2.09-3.65 times longer than that in the corresponding unsterilized soil, which indicated that microorganisms were the predominant contributors for the dissipation of napropamide in soil. Uptake and bioaccumulation of napropamide in soil by earthworm Eisenia foetida also mainly depended upon soil properties, especially the level of OM content (P<0.05). The K_f values of napropamide were negatively correlated with t₅₀ (r=-0.885, P<0.05) and the bioaccumulation factor (r=-0.796, P<0.05). The corresponding linear regression equation was t₅₀=94.210-3.535 K_f and BAF=0.264-0.014 K_f, respectively. The results here revealed the potential of using the adsorption coefficient K_f as the model to evaluate the persistence and bioavailability of napropamide in soil.