A Study On The Environmental Behavior And Residual Dynamics In Wheat Environmental Of Dinotefuran

Dinotefuran is an insecticide of the neonicotinoid class developed by Mitsui Chemicals,its mechanism of action involves disruption of the insect's nervous system by inhibiting nicotinic acetylcholine receptors.Dinotefuran has obvious control of insect pests such as aphids,whiteflies,thrips,leafhoppers,leafminers,sawflies,mole cricket,lacebugs,billbugs,beetles,mealybugs,and cockroaches.At present,the report about residue and degradation of dinotefuran is little.In this study,the environment behavior(hydrolysis,photolysis,soil degradaton,absorption and mobility)and residual digestion dynamics of dinotefuran were systematically studied.These results provided scientific bases for reasonable using and evaluating environmental safety of dinotefuran.The main results were as follows:1.An analytical method was developed for dinotefuran residues in soil,wheat and plant samples.The samples were extracted with acetonitrile and purified by solid phase extraction(SPE),and determined by HPLC with UV detector.At the spiked concentrations of 0.05-1.0 mg/kg,the average recoveries were 83.29-96.93%,and the relative standard deviations(RSD)ranged from 0.29%to 2.91%.The limit of quantification(LOQ)was 0.05 mg/kg.The analytical method meets the requirement of residual determination of dinotefuran.2.The results of residues degradation dynamics of dinotefuran with two formulations at three wheat paddy fields of Jiangsu,Henan,Hebei showed that the degradation dynamics accord with the kinetic equation.The half life(ti/2)of 20%dinotefuran soluble granule(SG)was 1.85-2.62 d in wheat plant,4.87-5.44 d in soil.The results of the final residue experiments showed that the final residues of dinotefuran at 21 d after last application were the maxium residue 1.071 mg/kg in plant,under 0.05 mg/kg in soil and wheat.The half life(t1/2)of 20%dinotefuran suspension concentrate(SC)was 1.36-4.19 d in wheat plant,6.40-7.71 d in soil.The results of the final residue experiments showed that the final residues of dinotefuran at 21 d after last application were the maxium residue 1.394 mg/kg in plant,0.119 mg/kg in wheat,and under 0.05 mg/kg in soil.The dosage of 20%dinotefuran SG is below 60 g a.i/ha,by spraying 2 or 3 times in Aphid occurrence with the interval of 21 d.The dosage of 20%dinotefuran SC is below 120 g a.i/ha,by spraying 2 or 3 times in Aphid occurrence with the interval of 21 d.3.The result of hydrolysis test showed that dinotefuran belongs to hard hydrolysis pesticides.The hydrolytic rate of dinotefuran in different pH value buffers showed the following sequence:pH 9>pH 7>pH 5,pH was a decisive factor for the effect of hydrolysis.Temperature also had an effect on dinotefuran hydrolysis,which was increased with temperature increasing.SDS could significantly restrain the hydrolysis rates of dinotefuran and the restraining degree was enhanced with the increasing concentration of SDS.Humic acid could promote the hydrolysis rates of dinotefuran and the promoting degree was enhanced with the increasing concentration of humic acid..And the hydrolysis rate of dinotefuran in the natural environment was faster than in the labortory.4.The photo-degradation of dinotefuran was studied under the irradiation of Xenon lamp.The results showed that the photolytic rate was negatively correlated with the increasing concentration of dinotefuran in aqueous solution at ranged from 5 to 40 mg/kg.The photolytic rate of dinotefuran in three optical source was followed by high pressure mercury lamp>ultraviolet lamp>Xenon lamp,the photo-degradation of dinotefuran was increased with light intensity increasing.The photolytic rates of dinotefuran in four organic solvents showed the following sequence:n-hexane>acetonitrile>methanol>ethyl acetate.The photolytic rate of dinotefuran in alkaline buffer solution was much faster than in acid buffer solution.Fe3+ could promote the photolytic rates of dinotefuran and the strongest promoting was presented at the concentration of 1.0 mmol/L.Fe2+ could restrain the hydrolysis rates of dinotefuran and the restraining degree was enhanced with the increasing concentration of Fe2+.5.The degradation and the influence factors of dinotefuran in three kinds were studied in the laboratory.The results showed that the degradation rates followed the sequence:Nanjing yellow-brown soil>Northeast China black soil>Jiangxi red soil.The increased moisture accelerated the decay of dinotefuran in soil,the decay was slower at 80%moisture treatments because microbial organisms growth was inhibited.Microbial organisms and organic matter play an important role in the process of soil degradation.6.The adsorption ability of dinotefuran in three kinds of soils following the sequence:Northeast China black soil>Nanjing yellow-brown soil>Jiangxi red soil.The results of soil Thin-Layer Chromatography(TLC)showed that the Rf were 0.77,0.87 and 0.55 in Nanjing yellow-brown soil,Jiangxi red soil and Northeast China black soil,respectively.Dinotefuran was removable in Nanjing yellow-brown soil and Jiangxi red soil,and medium-mobile in Northeast China black soil.The results of Soil Column Leaching showed that 37.4%and 65.0%of dinotefuran were leached out in Nanjing yellow-brown soil and Jiangxi red soil.The pesticide mainly remained in a distance of 10.0-30.0 cm in Northeast China black soil.These results demonstrate that dinotefuran has potential risk for contaminating groundwater,especially for yellow-brown soil and red soil.