Effects Of Dissolved Organic Matter And Microplastics On Adsorption And Desorption Behavior Of Triflumezopyrim In Soil

Triflumezopyrim(TMP)is a novel mesoionic or zwitterionic insecticide.It acts on the nicotinic acetylcholine receptors of insects,blocks the neurotransmission of pests,and ultimately affects the normal physiological behavior of pests leading to death.The primary application of this product is for the management of rice planthoppers,leaf hoppers,and other rice pests.The adsorption and desorption behavior of pesticides in soil determines their migration,retention,transformation,and bioavailability in soil,which is an important process controlling the environmental behavior of pesticides and an important index for the environmental safety evaluation of pesticides.Therefore,it is of great significance to study the adsorption and desorption of pesticides in soil for rational application of pesticides and reduction of environmental pollution.Studies have shown that dissolved organic matter(HA)and microplastics(MPs)can change the environmental migration behavior of organic pollutants in soil,Therefore,more attention should be paid to the effects of dissolved organic matter and microplastics on the migration and bioavailability of trifluoropyrimidine in soil.In this paper,the adsorption and desorption characteristics of TMP in five different soils were investigated using the oscillatory equilibrium method,The effect of adding dissolved organic matter and microplastics on adsorption and desorption of TMP in soil was studied.The main results are as follows:(1)The adsorption kinetics and adsorption-desorption isotherm characteristics of TMP in five different soils from Jilin,Jiangsu,Jiangxi,Guangxi,and Hainan were investigated using the oscillatory equilibrium method.Furthermore,the impact of environmental factors such as on the adsorption behavior of TMP in soil was evaluated.The results indicate that the adsorption and desorption isothermal of TMP in five soils were consistent with the Freundlich equation,and the adsorption constants of TMP in five soils were 7.62,5.88,3.30,4.78,and 1.88 respectively.With the increase in temperature,the adsorption capacity of TMP increased gradually,and the Gibbs free energy was negative,indicating that TMP was mainly physical adsorption.The adsorption capacity of soil to TMP decreased with the decrease in pH.The hysteresis coefficient of TMP in the soil is greater than 1(except in Guangxi),and there is a hysteresis phenomenon,TMP is not easy to be adsorbed by soil,is easy to desorption from the soil,and has certain migration characteristics.(2)The effect of two kinds of dissolved organic humic acid(HA)and fulvic acid(FA)on the adsorption and desorption behavior of TMP in soil was studied.The results showed that the presence of dissolved organic matter shortened the adsorption equilibrium time and increased the adsorption capacity of TMP.Adsorption kinetics results are consistent with the pseudo-second-order kinetic equation and reflect the entire process of adsorption.According to the Freundlich equation data of adsorption and desorption isotherm,the presence of dissolved organic matter enhanced the adsorption and desorption capacity of soil to TMP,and the adsorption capacity of soil containing HA was greater than that of FA,which was primarily due to the high molecular weight and aromaticity of HA.(3)The effect of adding two different types of microplastics,Poly(butylene succinate)microplastics(PBS)and Polypropylene microplastics(PP),on the adsorption and desorption behavior of triflumezopyrim in soil was investigated,and the adsorption mechanism of microplastics was discussed.The results showed that when 1%of PBS and PP were added to five different types of soil,compared to the blank control soil,the PBS and PP enhanced soil adsorption and desorption ability to TMP,and the adsorption and desorption behavior of different types of microplastics to triflumezopyrim in the soil had obvious differences.The adsorption capacity of the soil containing PBS was substantially greater than that containing PP,and the desorption capacity of the soil containing PP was lower than that containing PP.By studying the adsorption mechanism of microplastics on TMP,the values of Cs and KF calculated by the pseudo-second-order adsorption kinetics and adsorption isotherm equation follow PBS>PP,SEM images demonstrate that there are more adsorption sites on PBS,while FTIR and XRD analyses show that the adsorption of microplastics on TMP is mainly physical adsorption.