Effects Of Joint Pollution Of Three Pesticedes,Surfactants And Microplastics On The Degradation Of Pesticides

Part of pesticides will enter the environment through drifting,sedimentation,etc.after application.Furthermore,pesticides will undergo a series of environmental behaviors such as migration,degradation and transformation under the combined action of physical,chemical and biological factors,which are harmful to non-target organisms and even humans.Among them,degradation is one of the important environmental behaviors of pesticides.Studying the degradation behavior of pesticides is of great significance for guiding the rational use of pesticides,scientific monitoring and pollution control.However,current studies have shown that environmental coexistents such as surfactants and microplastics can affect the degradation of pesticides,which means that using traditional single-factor methods to study the degradation behavior of pesticides cannot accurately reflect the true status of pesticides in the environment,cannot correctly understand their true degradation characteristics and environmental fate,which may underestimate the environmental risks and potential hazards.Therefore,this research uses this as an entry point,taking acetamiprid,dimethomorph,and pyridaben as the test pesticides.These three pesticides are currently on the market with high-efficiency,broad-spectrum and widely used insecticides,fungicides and acaricides.They have same registered crops,and there are actual pesticide mixture registrations for acetamiprid and pyridaben,which means that the three pesticides are very likely to co-exist in the environment and cause joint pollution.At present,there have been reported on the degradation of the three pesticides alone,but it is not clear whether the mixed use of the three pesticides will affect their degradation,and whether surfactants and microplastics have an impact on the degradation of the three pesticides.Therefore,this article uses the widely used new fluorosurfactants potassium perfluorooctyl sulfonate(FC-95)and perfluorooctyl quaternary ammonium iodide(FC-134)as the test surfactants,the degradable microplastics which are currently widely used in the production of mulch film polylactic acid(PLA)and polybutylene succinate(PBS)as the test microplastics to figure out the effects of joint pollution of three pesticides,surfactants and microplastics on the degradation of pesticides.This will provide theoretical basis and guidance for the rational use of pesticides and pollution control.The main results of this paper are as follows:1.The instrumental analysis method of acetamiprid,dimethomorph and pyridaben was established by HPLC equipped with EC-C18 chromatographic column.When the mobile phase is acetonitrile and water,the column temperature is 35 ℃,and the UV detection wavelength is 225 nm,the three pesticides can achieve baseline separation within20 min.Using the Qu Ch ERS method,the pretreatment method of three pesticides in water and soil matrices was established.This method has no obvious matrix effect,the recovery rate is 94.6%-105.8%,and the RSD is 3.9%-11.4%.The accuracy and precision of the method are good and meet the test requirements.2.The effects of the mixed use of three pesticides on their photolysis in aqueous solutions and on soil surface were studied under simulated indoor conditions.(1)The results of the photolysis test in aqueous solution show:(1)Dimethomorph,pyridaben and their mixture can inhibit the photolysis of acetamiprid,and the inhibition factor is 1.85-3.19times;(2)Similarly,acetamiprid,pyridaben and their mixtures can also inhibit the photolysis of dimethomorph,with an inhibition factor of 1.20-1.31 times;(3)However,dimethomorph has no significant effect on the photolysis of pyridaben.Acetamiprid and their mixtures canl inhibit the photolysis of pyridaben by 1.32 times and 2.22 times,respectively.(2)The results of the photolysis test on soil surface show:(1)Dimethomorph,pyridaben and their mixture inhibit the photolysis of acetamiprid,the inhibition factor is1.21-1.75 times;(2)Acetamiprid,pyridaben and their mixture promote the photolysis of dimethomorph,and the promotion factor is 1.36 to 1.77 times;(3)Similarly,acetamiprid,dimethomorph and their mixture can also promote the photolysis of pyridaben with a promotion factor of 1.27-2.17 times.3.The influence of the mixed use of three pesticides on its hydrolysis was studied under simulated indoor conditions.The results show:(1)Dimethomorph,pyridaben and their mixture can inhibit the hydrolysis of acetamiprid,and the inhibition factor is 2.19-2.98times;(2)Similarly,acetamiprid,dimethomorph and their mixtures can also inhibit the hydrolysis of pyridaben,with an inhibition factor of 1.74 to 3.03 times.4.The effects of two surfactants on the photolysis in aqueous solutions and hydrolysis of three pesticide were carried out under simulated indoor conditions.(1)The results of the photolysis test in aqueous solution show:(1)FC-95 can inhibit the photolysis in aqueous solutions of three pesticides,with an inhibition factor of 1.18-2.42 times;(2)FC-134 can inhibit the photolysis of acetamiprid and dimethomorph,and the inhibition times are 1.69 and 1.89 times,respectively.But it has no obvious effect on the photolysis of pyridaben.(2)The results of the hydrolysis test show:(1)FC-95 can inhibit the hydrolysis of acetamiprid by 4.25 times,but has no obvious effect on the hydrolysis of pyridaben;(2)FC-134 can inhibit the hydrolysis of acetamiprid and pyridaben,and the inhibition times are 4.20 and1.60 times,respectively.5.The effects of two microplastics on soil degradation of three pesticides were carried out under simulated indoor conditions.The results show:(1)PLA can inhibit the soil degradation of dimethomorph and pyridaben with the inhibition multiples of 2.06 and 1.50,respectively,but has no obvious effect on the soil degradation of acetamiprid;(2)PBS can inhibit the soil degradation of the three pesticides,and the inhibition factor is 1.70-3.00 times.