| The release, accumulation, and transportation of pesticide metabolite are gradually acquired more attention, since they can influence and even determine the safety for parent pesticide in environment and non-target organisms to some extent.3,5,6-TCP as the main metabolite of Chlorpyrifos pesticide present different physico-chemical properties and extremetly high risk in environment due to its high solubility in water and hard adsorption by soils. Currently, Chlorpyrifos replaced of Methamidophos has been applied on a large scale. Under this background, it is very important to conduct a systematic study on the environment behavior of3,5,6-TCP for making good use of Chlorpyrifos and weakening the environmental risk. Thus, in this paper, the determination methods of Chlorpyrifos and3,5,6-TCP in soil, plant, and water body were built up, and the environment behavior of3,5,6-TCP in soil, such as adsorption, degradation, and mobility have been investigated. The major findings are as follows:1. The determination methods of Chlorpyrifos and3,5,6-TCP in soil, plant, and water body were built up. These methods were simple, rapid, accurate, and sensitive. The regression equation of Chlorpyrifos and3,5,6-TCP standard contents vs. peak areas were:Y=249475x-4608.2(r2=0.99913) and Y=356093x-2215.9(r2=0.99995), respectively; The limit of detection (LOD) of instrument and methods for Chlorpyrifos and3,5,6-TCP were:0.003μg·mL-1and0.03μg·g-1,0.0004μg·mL-1and0.0005μg·g-1, respectively; Under each level, the recoveries of Chlorpyrifos and3,5,6-TCP by external addition method were64.3～90.0%and54.2%～78.1%, respectively. The RSD%was less than5%.2. The adsorption-desorption behavior of3,5,6-TCP on six soils were studied. The results showed:(1) The content of organic matter and pH of soil could affect the adsorption behavior of3,5,6-TCP and the correlation equation was observed as Kd=1.67+0.094(%OC)-0.14(pH), R2=0.894.(2) The Kd values for3,5,6-TCP adsorption on different soils followed the order:red soil (1.3mL·g-1)> black soil (1.26mL-g’)> limestone soill (0.96mL·g-1)> cinnamon soil (0.72mL·g-1)> fluvo-aquic soil (0.68mL·g-1)> purplish soil (0.50mL·g-1).3,5,6-TCP in limestone soill, cinnamon soil, fluvo-aquic soil, and purplish soil showed potential leaching risk due to their lower Kd values.(3) The hysteresis effect of3,5,6-TCP desorption from six soils was found, and the desorption rate was higher than the adsorption rate.3. The adsorption-desorption of3,5,6-TCP on kaolinite and montmorillonite were studied and the effects of the content of organic matter, pH, and ion strength were analyzed. The result showed:(1) The similar adsorption behaviors of3,5,6-TCP on kaolinite and montmorillonite were found with the characteristics of linear and irreversible adsorption without hysteresis effects. The Kdads values for kaolinite and montmorillonite were1.169and1.237mL·g-1, respectively, while the Kddes values were3.912mL·g-1and4.883mL·g-1.(2) pH could obviously influence the adsorption-desorption behaviors of3,5,6-TCP in kaolinite and montmorillonite. The maximum adsorption capacities of3,5,6-TCP on kaolinite and montmorillonite were observed when pH values in environment were4.5and6.0, respectively.(3) The adsorption strength increased as a function of organic matter content. When the content of organic matter was less than1%, the adsorption sites were mainly provided by kaolinite and montmorillonite. When the content of organic matter was more than2%, the adsorption of3,5,6-TCP on kaolinite and montmorillonite was improved by adding organic matter. The multiple increase of Kd value was also obtained with the increase of organic matter.(4) Insignificant effect was found for the adsorption of3,5,6-TCP on kaolinite and montmorillonite.4.,The degradation behaviors of3,5,6-TCP and Chlorpyrifos in soil, plant, and water body were compared and the accumulation, release, and degradation behaviors of3,5,6-TCP were also investigated. The results indicated (1) At25℃, The DT50of Chlorpyrifos and3,5,6-TCP in five soils (red soil, black soil, limestone soil, fluvo-aquic soil, and cinnamon soil) were11.8-31.2d and24.0～69.1d, respectively. While these in water body were0.07～4.8d and29.7～57.7d.(2) With the recommended dose of Chlorpyrifos, at4d～14d after application,3,5,6-TCP could be detected out and the peak amounts with0.33μg·g-1in plant and with0.21μg·g-1in soil were observed.(3) The peak amounts of3,5,6-TCP in five soils were related with the DT50of Chlorpyrifos. At11.8～31.2d, the peak amounts of3,5,6-TCP of0.63～1.21μg·g-1in five soils were received. While at0.07～4.8d, the peak amounts of3,5,6-TCP in water body was0.17～0.36μg·mL-5. The leaching behaviors of3,5,6-TCP and Chlorpyrifos were compared. The results showed (1)68.9～89.6%of Chlorpyrifos were adsorbed by five soils and no Chlorpyrifos were detected out in eluate.3,5,6-TCP could move27cm in column loaded with five soils and10.3%～34.4%of which was adsorbed during leaching process.(2) The BTCs of3,5,6-TCP in five soils were followed in order of black soil (4.31)> red soil (4.24)> limestone soill (3.95)> fluvo-aquic soil (3.28)> purplish soil (2.36). The GUS index larger than2.8indicated that3,5,6-TCP was extremely and easily leachable in five experimental soils. |
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