The Fate Of Trichlorfon And Dichlorvos In Carrot Field And Their Absorption On Soil

Trichlorfon and Dichlorvos are both organophosphorus pesticides,commonly used to control crop pests.In order to understand and evaluate its behavior in the environment more accurately,this paper studied and determined the residual detection method of Trichlorfon and Dichlorvos in carrot samples such as carrots,soil and carrot plants.The residual digestion of several samples in carrot field in Changsha,Hunan and other five regions was systematically analyzed.And the adsorption behavior of Trichlorfon and Dichlorvos in two typical kinds of farmland soils of Hunan was studied,it provides reference to rational use and scientific control of Trichlorfon and Dichlorvos on carrots.The main conclusions are as follows:?1?The method of gas chromatography analysis and detection of the residues of Trichlorfon and Dichlorvos in carrots,soils and carrot plants was established.When the concentration of Trichlorfon in the sample was 0.05mg/kg-5.0mg/kg,the average added recoveries ranged from 74.9%-104.3%,the relative standard deviation was between 3.1%and 9.3%The minimum detection concentration?ie,quantification limit?in carrots,soils and carrot plants was 0.05mg/kg.When the concentration of Dichlorvos was 0.02mg/kg to 2.0mg/kg,the average added recoveries of Dichlorvos was between 74.7%and 106.6%,the relative standard deviation was between 2.7%and 9.3%.The minimum detection concentration?ie,quantification limit?of Dichlorvos in carrots,soils and carrots was 0.01mg/kg.?2?The digestion of Trichlorfon in carrot plants and soils in Changsha and Shijiazhuang coincided with the first order chemical reaction equation:C_t=C₀e^-kt,the digestion half-life of two samples were 3.63d³.89d and 3.90 d.And the digestion of Dichlorvos in carrot plants and soils is too fast to collect enough digestion data.It showed that Trichlorfon and Dichlorvos in the carrot field were easily degraded,and they would not cause cumulative residues.?3?The adsorption equilibrium time of Trichlorfon and Dichlorvos in the two kinds of soils tested was about 16h.The adsorptive capacity of Trichlorfon and Dichlorvos in alluvial soil was higher than that in the Quaternary red soil The adsorption capacity of Trichlorfon and Dichlorvos in soil was greatly affected by pH,it decreased with the decreasing of pH.The adsorption capacity of the two insects in the soil increased with the temperature increasing,and the optimum temperature of adsorption is 25?.The order of the four kinds of biochars for increasing the soil adsorption capacity was:Coconut shell biochar>Nut biochar>charcoal biochar>rice husk biochar.?4?Freundlich equation?r?0.950,n=7?and Linear adsorption isotherm model?r?0.991?can properly describe the isothermal adsorption process of Trichlorfon and Dichlorvos in two kinds of soils tested,the correlation coefficient both reached a significant level?p<0.01?.