毒死蜱土壤环境行为研究进展

Progress on environmental behavior of chlorpyrifos in soils

有机磷农药毒死蜱广泛使用带来的环境问题日益受到关注。本文针对毒死蜱在土壤中的环境行为,综述了毒死蜱在土壤中吸附解吸、降解及归趋研究进展,探讨了毒死蜱污染土壤环境中环境行为的主要影响因素。毒死蜱在土壤中的吸附解吸过程是与表面吸附位点相关的物理过程,降解过程是以细菌、真菌为主的生物降解过程。毒死蜱在土壤中迁移转化受土壤理化性质、种植作物类型等因素影响,而不同影响因子对毒死蜱在土壤中迁移转化的交互影响机制目前尚不明确。建立多因素吸附解吸模型,考虑土壤环境中复杂因素交互作用,对研究毒死蜱在土壤中的环境行为及其驱动机制具有重要意义。

Chlorpyrifos（O, O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate, CPF） is one of the most widely used pesticides in agriculture, with broad-spectrum, high efficiency, and moderate toxicity. Unfortunately, only less than1% of CPF applied can be directly utilized by plants, and up to 99% were released into the environment. Continuous and excessive use of CPF has already led to widespread environmental contamination. Recently, great concern has been raised regarding its residue problems and the risk to the ecological environment. In this paper, the fate and environmental behavior of CPF in soils were reviewed. Adsorption/desorption and degradation were two critically important courses on this issue. CPF adsorption/desorption in soils may be fitted by Freundlich model or linear model. The parameters of CPF adsorption in soils are greatly related to soil properties. Soil organic matter contents are the key parameter controlling CPF＇s adsorption, as well as CPF＇s desorption. However, adsorption process is also affected by other soil characteristics, such as p H and temperature. It is therefore generally assumed that the sorption mechanisms of CPF in soils should be dominated by the binding between CPF and the hydrophobic site on the surface of soil particles. The degradation of CPF in the natural environment is mainly controlled by biotic processes. Bacteria and fungi are the main microorganisms that can degrade CPF by co-metabolism or mineralization into 3,5,6-trichloro-2-pyridinol and dicethylthiophospshate. The degradation of the intermediate degradation product 3,5,6-trichloro-2-pyridinol is the limiting factor for the CPF degradation process.Indigenous microorganism is effective for the degradation of 3,5,6-trichloro-2-pyridinol, leading a good remediation of CPF contaminated site. The use of indigenous or genetically modified microorganisms and/or plants has enhanced the degradation for in-situ bioremediation of contaminated sites. In conclusion, it is necessary to establish an adsorption/desorption model to describe the complex relation between CPF and other factors in soils. Furthermore, a novel gene technology can be further studied to enhance the degradation of CPF by microorganism and/or plants in soils.