Study On The Sedimentary And Metabolic Law Of Procymidone In Rape Planting System

Procymidone is a new type of low-toxic,bioabsorbable bactericide developed by Sumitomo Chemical Industry Co.,Ltd.in Japan.Its mechanism of action is to inhibit the synthesis of triglyceride in the bacteria.It is widely used to prevent botrytis and sclerotia in fruits and vegetables because of low cost and good control effect.This paper clarified the deposition law of procymidone in different parts of rape planting system in Jiangsu,Qinghai and Hunan and put forward the environmental risk of procymidone to honeybee,earthworm and bird,the application limit standard of humus on rapeseed was calculated..The soil surface photolysis and soil degradation of procymidone were studied by a laboratory simulation test system.The absorption and metabolism of procymidone in rape plants and water medium were studied.Metabolites of procymidone in rape plants,soil and water medium were found by high resolution liquid chromatography-mass spectrometry.In addition,the effect of biochar on the adsorption and degradation of procymidone in soil and the effect of procymidone on greenhouse gas emission in rape ecosystem were studied.The main research results are as follows:1.The deposition law of procymidone in different parts of rape planting system in Jiangsu,Qinghai and Hunan was studied.The results showed that the deposition amount of procymidone in rape flowers,stems and soil increased with the increase of doses under five doses of 150 g ai/ha,225 g ai/ha,300 g ai/ha,450 g ai/ha,600 g ai/ha.That is,the deposition amount of procymidone in rape flowers,stems and soil was largest when the dose was 600 g ai/ha.The original deposition concentration of procymidone in different parts of rape was as follows:flower>lower part of stem>soil,comprehensive analysis of three rape substrates.2.Based on the residue data of procymidone in rape planting system in Jiangsu,Qinghai and Hunan,the environmental risk of procymidone to honeybee,earthworm and bird and the application limit of procymidone were evaluated.The risk quotient(RQsp)for honeybees was 0.12 and less than 1,indicating that the risk of procymidone to honeybees was acceptable after application of procymidone to rape.The risk quotient(HQin)for earthworm was 0.0004(less than 1),indicating that the risk of procymidone to earthworm was acceptable after application of procymidone to rape.The acute risk quotient(RQacute),short-term risk quotient(RQshort-term)and long-term risk quotient(RQlong-term)of procymidone to birds were 0.0491,0.0202 and 1.1112,respectively.The acute risk quotient value(RQacuTe)and short-term risk quotient value(RQshort-term)were less than 1,but the long-term risk quotient value(RQlong-term)was greater than 1,which indicated that the acute risk and short-term risk of procymidone to birds were acceptable after application of procymidone to rape.But there was a certain long-term risk to birds.The lowest effective control dose of procymidone was the lower limit of the application limit,and the lowest dose of food and environmental safety was the upper limit of the application limit.The standard of application of procymidone on rape was 150～540 g ai/ha.3.The soil surface photolysis and soil degradation of procymidone were studied by a laboratory simulation test system.The absorption and metabolism of procymidone in rape plants and water medium were studied by the experiment of hydroponic rape plants.Metabolites of procymidone in rape plants,soil and water medium were found by high resolution liquid chromatography-mass spectrometry.The results showed that the photolysis kinetics of procymidone on the soil surface satisfied the first-order kinetics equation.The photolysis half-life was 6.9 d,which was medium photolysis pesticide.The degradation kinetics of procymidone in the soil satisfied the first-order kinetics equation.The degradation half-life was 30.7 d,which was medium degradation pesticide.In the first 7 days of the experiment of hydroponic rape plants,the content of procymidone in water medium decreased with the increase of procymidone in rape plants,while only 1.76%procymidone in the water medium of the dark control degraded,which indicating that most of the decreased procymidone in water medium was absorbed by rape plants.Then procymidone decreased in rape plants with time,which was also the metabolic process of procymidone in rape plants.High resolution liquid chromatography-mass spectrometry was used to found one photolysis product of procymidone on soil surface,it was M1 m/z=249.0557.Three degradation products of procymidone in soil were found,they were M1 m/z=249.0557,M2 m/z=301.0272,M3 m/z=160.9799,respectively.One metabolites of procymidone in rape plants were found,it was M1 m/z=249.0557.Four metabolites of procymidone in water medium were found,they were M2 m/z=301.0272,M3 m/z=160.9799,M4 m/z=317.0222,M5 m/z=299.0116,respectively.The compounds of M1 and M3 were first found in soil.The compounds of M1 was first found in rapr plants.The compounds of M2 and M4 were first found in water medium.4.The effect of rice husk biochar,fruit shell biochar and coconut shell biochar on the adsorption and degradation of procymidone in soil was studied.The adsorption behavior of procymidone in 0.5%rice husk biochar soil,0.5%fruit shell biochar soil,0.5%coconut shell biochar soil and control soil all conformed to the Freundich equation.The order of the adsorption capacities of the four soils for the procymidone was:0.5%rice husk biochar soil>0.5%fruit shell biochar soil>0.5%coconut shell biochar soil>control soil,adsorption constants were 325.03,250.95,101.83 and 22.95,respectively.The degradation behavior of procymidone in 0.5%rice husk biochar soil,0.5%fruit shell biochar soil,0.5%coconut shell biochar soil and control soil all conformed to the Freundich equation.The order of the degradation capacities of the four soils for the procymidone was:control soil>0.5%coconut shell biochar soil>0.5%fruit shell biochar soil>0.5%rice husk biochar soil,the degradation half-lives were 30.7,60.8,177.7 and 385,respectively.The degradation rate of procymidone was the slowest in the soil with the strongest adsorption capacity.5.The effect of procymidone on greenhouse gas emission in rape ecosystem was studied by pot experiment in laboratory simulation.The results showed that the emission of greenhouse gas CH4 and N2O of rape ecosystem didn’t significantly differ with that of blank control because of the application of 30 mL 5 mg/L and 10 mg/L procymidone,but the emission of greenhouse gas CO2 increased significantly because of the application of procymidone.Compared with blank control,the emission of greenhouse gas CO2 of rape ecosystem with application of 30 mL 5 mg/L procymidone increased 135%,the emission of greenhouse gas CO2 of rape ecosystem with application of 30 mL 10 mg/L procymidone increased 177%,what’s more,the emission of greenhouse gas CO2 of rape ecosystem with application of 30 mL 10 mg/L procymidone was more 18%than that of 30 mL 5 mg/L procymidone.