Effects Of Copper On Environmental Behavior Of Pyrethroid Pesticide And Eco-effect Of Combined Pollution

Pesticides and heavy metals pollution in soft environment has become a serious problem in many countries including China.However,little attention has been given to determine combined effect of heavy metals and pesticides on the environment.Therefore,the aim of the present work was to examine the effect of Cu on the adsorption,transport,and degradation of pyrethroids in soils,and to investigate the eco-effect of combined pollution between Cu and pyrethroids on soil enzyme activity and soil microorganism.The main contents are as follows:(1) Batch equilibrium tests were conducted to examine the effect of Cu on the adsorption of lambda-cyhalothrin(λ-CHT) and cypermethrin (CPM) on two typical Chinese soils(black soil and red soil) with different soil characteristics.The probable adsorption mechanisms ofλ-CHT and CPM on soils were also revealed.The results showed thatλ-CHT showed a significantly stronger adsorption than CPM on both soils.Black soft had a stronger adsorbability than red soil to both pyrethroids,because of its larger organic matter and surface area.As the soil Cu concentrations increased from 19(or 18) mg·kg^-1 to 1600 mg·kg^-1,the adsorption coefficient ofλ-CHT and CPM decreased on both softs.This is mainly due to a competition between Cu and pyrethroids for occupying the adsorption sites on soils.(2) Thin layer chromatography(TLC) was used to investigate the effect of Cu on the transport of CPM andλ-CHT in soft.Without the addition of Cu,the Rf value of CPM in red soil and black soft was 0.055 and 0.046,respectively.λ-CHT had the lower Rf value than CPM.The transport of CPM andλ-CHT was weak and the gradation of their transferability was I grade.As Cu concentration of spread solution increasing from 1 to 100 mg/L,Cu also increased the Rf value of CPM andλ-CHT.The results showed that Cu could promote pyrethroids to transfer in soil.(3) Laboratory studies were conducted to investigate the influence of Cu on the hydrolysis,photo-degradation and soil degradation of CPM andλ-CHT.A number of degradation products had been characterized and identified by gas chromatography-mass spectroscopy(GC-MS). Degradation pathways were also proposed.The hydrolysis of CPM andλ-CHT was rapid as the pH of the solution increasing from 5 to 9.The addition of Cu could promote the hydrolysis of CPM andλ-CHT.This is related with a chelation between Cu and pyrethroids.Appropriate application of Cu could promote the photodegradation of CPM andλ-CHT, but it could reduce the degradation of these pyrethroids pesticides in soil.(4) The effect of pyrethroids and Cu on soil enzyme activities,soil respiration and soil microbial biomass C was studied.The results showed that the catalase activity was declined after application of high concentrations of Cu and CPM.Combined pollution of Cu and pyrethroids had a positive influence on soil respiration.Soil microbial biomass C treated with Cu and pyrethroids was significantly lower than that of the control soil over the course of incubation.