Experimental Simulation Study On The Migration And Transformation Of Chlorpyrifos In Paddy Soil-overlying Water System

The widespread use of organophosphorus pesticide,chlorpyrifos,leads to serious ecological environment problems while improving the crop yields.The distribution,migration and transformation characteristics have become a focus in the environmental research field.The application of chlorpyrifos in agricultural production is gradually attracting more and more attention,so it is necessary to comprehensively evaluate the migration and transformation of chlorpyrifos rules in the paddy soil-overburden system and the residual content distribution characteristics of chlorpyrifos in different media.Therefore,taking the rice field in the red soil hilly area as the object,through batch balance experiment,indoor simulation experiment and field plot experiment,the study mainly analyzed the migration characteristics and adsorption mechanism of chlorpyrifos and its main degradation product 3,5,6-trichloro-2-pyridinol(TCP)in different soil depths comprehensively,also discussed the influence of temperature and microorganisms on the migration and transformation of chlorpyrifos in the soil-overlying water system.At the same time,it analyzed and summarized.The distribution characteristics of chlorpyrifos in different media in the field environment.The main findings were as follows:(1)The residual level of chlorpyrifos and TCP in red paddy soil was as follows:In the batch balance experimental system,chlorpyrifos was easily adsorbed by the solid phase of the soil(90%-95%),and TCP was weakly adsorbed by the soil,but it mainly retained in the water phase(60%～75%),the difference of soil organic matter content had a significant impact on the adsorbability of chlorpyrifos and TCP.(2)The results of laboratory simulation showed that the temperature and microorganisms had a synergistic effect on the migration and transformation of chlorpyrifos in the soil-overlying water system.Chlorpyrifos quickly dissipated in the early stage,but slowed down in the later stage in the overlying water,with a low residual rate in the overlying water but a high residual rate in the soil,it was mainly adsorbed by the surface soil.The variation trend of TCP was complementary to the digestion trend of chlorpyrifos in the overlying water,which was greatly affected by environmental temperature and was easily accumulated.It also showed that TCP was the main degradation product of chlorpyrifos in the experiment.(3)Field trials found that chlorpyrifos was easy to leachate and migrate to deep soil(up to 50cm)in the acid red paddy soil;the profile distribution characteristics of chlorpyrifos in paddy soil generally showed that the content of chlorpyrifos decreased slightly with the deeper soil depth,and the content reached the highest at the 0-5 cm depth of soil surface.meteorological environment factors(temperature,wind and rainfall events,etc.)will would affect the digestion of chlorpyrifos in field water and soil pore water;Different irrigation methods had a significant effect on the residual amount of pyrifos in different parts of rice at harvest time.