Exploratory Studies On The Residue And Environmental Behavior Of High-risk Pesticide Adjuvants In Soils

Pesticide adjuvants as one of the major components of pesticides, their environmental pollution problems have received increasing attention. The safety management of pesticide adjuvants have been putting on the agenda. New pesticide additives which are green, safe, efficient and environmentally friendly are on the rise. In this condition, it has important practical significance to investigate the residues of high-risk pesticide adjuvants on soils and exploratory study their environmental behavior.It will enhance the safety management of pesticide adjuvant and promote the sdtuy of new green pesticide adjuvant.Residues of two high-risk pesticide adjuvants, Nonylphenol (NP), nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylates (NP2EO) and Bis (2,3,3,3-tetrachloropropyl) ether (S421), in agricultural soil of Heilongjing province were investigated by using high performance liquid chromatography - mass spectrometry and gas chromatography ion in this thesis. The degradation, sorption and leaching characteristics of Nonylphenol and Bis (2,3,3,3-tetrachloropropyl) ether in Heilongjiang black soil, Beijing fluvo-aquic soil, Guangxi red soil were also investigated in laboratory. The main results were as follows:Investigation results of the two high-risk pesticide adjuvants in Heilongjiang soils showed that the two substances were detected in different content, with Nonylphenol ethoxylates were more serious than Bis (2,3,3,3-tetrachloropropyl) ether. Among the Nonylphenol ethoxylates degradation metabolites, NP was higher than those of NP1EO and NP2EO, which implied that the degradation of NP was relatively difficult and easily accumulated in soil. NP, and S421 concentrations in the topsoils were ND ~ 156.8μg/kg, ND ~ 15.70μg/kg, ND ~ 13.63μg/kg and ND ~ 19.66μg/kg,with the mean of 22.02μg/kg, 4.04μg/kg ,2.15μg/kg and 1.87μg/kg, respectively. And the residue levels in the topsoil of NP and S421 in Heilongjiang soil were agreed with other residue levels that have been reported, with the concentrations were inμg/kg level. NP in section plane soils mainly distributed in 0 ~ 20 cm soil layer, NP1EO and NP2EO were mainly in 0 ~ 10 cm soil layer, and S421 were mainly in 0 ~ 5 cm soil layer.Degradation experiment results showed that Nonylphenol and Bis (2,3,3,3-tetrachloropropyl) ether degradation in three soils can be well described by the first dynamic equation. The degradation trend of nonylphenol was fast at early phase, and then became slow. The degradation of NP was divided into fast-degradation phase and slow-degradation phase, and the degradation half-lifes (t1/2) in these two phases were 6.74 ~ 9.72 d and 70.02 ~ 78.77 d in different soils, respectively. The degradation trend of S421 was relatively flat, with the half-life were 16.95 ~ 40.29 d in three soils. The degradation rates of NP and S421 were both associated with soil organic matter content. The main reason for the existence of the slow-degradation phase may be that Nonylphenol has different combinations with soil and the degradability of different isomers is different.Adsorption experiment results show that the adsorption of NP in three soils fitted in linearly isotherms with adsorption constant (Kd) ranged from 31.66 to 65.52. And the adsorption of S421 fitted in Freundlich isotherms with Kd ranged from 8.10 to 18.30. Soil organic matter content was the first factor that affects NP and S421 adsorption in soils, the cation exchange capacity followed, and the clay content and pH were less affected. NP and S421 in soils both were not easy to migrate in soil.Leaching results show that the most NP and S421concentrations among six layers of soil column both were 0 ~ 5 cm layers under every different treatment of the experimental conditions. NP and S421 were less mobility and didn't leach through the soil column at most situations, only the S421 was detected in leaching water in the condition of high doses was used. The leaching strength of NP and S421 were related to the adsorption abilities. The adsorption stronger, the leaching was relatively weaker. The leaching depth of NP and S421 in soil column increased with the rainfall, adjuvants application doses, and initial soil water content.