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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(P<0.01)是影响敌草胺在土壤中吸附的主要因素,其次为黏粒含量(P<0.1)。敌草胺在土壤中的持久性较长,其降解过程符合一级动力学特征,降解速率随土壤有机质含量的升高而加快,半衰期(t50)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(P<0.05);敌草胺在土壤中的吸附系数与其半衰期(r=–0.885,P<0.05)、生物积累因子(BAF)(r=–0.796,P<0.05)之间均存在负相关关系,相应回归方程分别为t50=94.210–3.535 K_f和BAF=0.264–0.014 K_f,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。
Soil adsorption is the key factor controlling pesticide fate in the environment, and it is also one of the important factors that dominates the persistence and bioavailability of pesticides in the environment. In this paper, the adsorption, persistence and bioavailability of the herbicide dinitrate in soils with different properties were studied by high performance liquid chromatography (HPLC). The relationship between adsorption, soil durability and bioavailability of earthworm was studied. The results showed that the soil adsorption isotherms of the artemistigmine could be characterized by Freundlich model (r> 0.99) and the content of soil organic matter (P <0.01) in the range of tested concentration, The main factors, followed by clay content (P <0.1). The dithiocarbamate persistence is longer in the soil, and its degradation process accords with the first-order kinetic characteristics. The degradation rate is accelerated with the increase of soil organic matter content, and the half-life (t50) is between 61.3-97.6 d. The persistence of amines in soils was significant. Microbial degradation was the main pathway for the degradation of diclazuril in the soil environment. The half-life of soil-based antimicrobials was 2.09-3.65 times longer after sterilization. The absorption and bioaccumulation of enemy herbicide Eisenia foetida mainly depend on the soil properties, especially the soil organic matter content (P <0.05). The adsorption coefficient and its half-life of soil herbicide Eisenia foetida (r = -0.885, P <0.05) and BAF (r = -0.796, P <0.05). The corresponding regression equations were t50 = 94.210-3.535 Kf and BAF = 0.264-0.014 Kf, respectively, indicating that the adsorption coefficient It can be used as a model parameter to evaluate the persistency and bioavailability of dipropamide in soil.