Study On The Environmental Behavior Of Fluensulfone

Fluensulfone is a new heterocyclic fluoroalkenylsulfone nematicide developed by Andoma Company.It has a new mechanism of action,is friendly to non-target organisms,has no cross resistance with other commodities,and is widely used in agricultural production.However,long-term use may have adverse effects on human health and ecological balance.In order to understand the degradation law of fluensulfone in the environment and evaluate its safety to the ecosystem,the environmental behavior of fluensulfone in the aspects of hydrolysis,photolysis,soil degradation and soil adsorption and migration was studied by using the indoor simulation test method.The results are as follows:1.The effects of various factors such as temperature,pH,and environmental factors on its hydrolysis were investigated.The results showed that at 25℃,the degradation rate of fluensulfone was the highest under acidic conditions,with the shortest degradation half-life.At35℃,the degradation rate was the fastest under acidic conditions,and the degradation rate was basically the same under neutral and alkaline conditions.This trend also existed at 50℃.With the increase of temperature,the degradation rate of fluensulfone in water increases.The addition of surfactants SDBS and CTAB at concentrations of 100 and 300 mg/L can promote the hydrolysis of fluensulfone,and when the concentration is 500 mg/L,it changes from promotion to inhibition.Compared with distilled water,lake water and rainwater have a catalytic effect on the hydrolysis of fluensulfone,but degradation in them is difficult to degrade pesticides.Humic acids promote the hydrolysis of fluensulfone,and the higher the concentration,the greater the degradation rate.2.The influences of pH,light source,inorganic ions,humic acid and different water bodies on the photolysis of fluensulfone were explored.The results show that the half-lives of fluensulfone under 500 w xenon lamp,20 w ultraviolet lamp and sunlight are 6.07、0.17 and17.07 h,respectively.The photolysis rate of fluensulfone under ultraviolet lamp is much faster than that under xenon lamp and sunlight.In the buffer solution,the photolysis rate of fluensulfone is pH4>pH7>pH9 from large to small,but the photolysis rate is very small.Humic acid inhibited the photolysis of fluensulfone,and the inhibition effect increased with the increase of concentration.Different concentrations of Fe³⁺showed inhibitory effect on photolysis of fluensulfone,and the inhibitory effect increased gradually with the increase of Fe³⁺concentration.The photolysis effect of NO₃^-at different concentrations on fluensulfone was inhibited.The inhibition effect gradually increased when the concentration was 5 mg/L,and gradually decreased when the concentration was 10 mg/L.SDBS and CTAB showed an overall inhibitory effect on the photolysis of fluensulfone,and the inhibitory effect of CTAB was stronger than that of SDBS.The inhibitory effect of both of them was gradually strengthened in a certain concentration range,and weakened after exceeding this range.With the increase of initial concentration,the photolysis rate decreases and the half-life increases.The photolysis of different water bodies took distilled water as the reference object,and the photolysis of fluensulfone was inhibited in groundwater,lake water and rain water.The inhibition effect was in the order of lake water>rain water>groundwater from the largest to the smallest.The photodissociation of different water bodies under sunlight has the longest half-life in lake water,followed by distilled water,and the half-life of groundwater and rainwater is basically the same.3.The effects of soil type,soil moisture content,sterilization and removal of organic matter on soil degradation of fluensulfone were studied.The half-life of fluensulfone in paddy soil is the shortest,followed by black soil,moist soil and brown soil.The half-life in red loam is the longest,and the half-life in these five kinds of soil is 37.3,53.7,55.9,56.4 and 61.3 d,respectively.Within a certain range,the higher the water content is,the faster the degradation rate is.Under waterlogging conditions,the sulfoxide contained in soil dissolves in water to form a hydrolysis mode and does not degrade,indicating that the effect of bacteria in water environment on the degradation of pesticides is less than that of bacteria in soil.The effect of microorganism on soil degradation of fluensulfone was less than that of organic matter.4.The adsorption and migration characteristics of fluensulfone in soil were studied.The results showed that the Weber-Morris model was more consistent with the adsorption kinetics of fluensulfone.The adsorption was faster within 12 h,the adsorption was balanced at 48 h,and the adsorption capacity increased from small to large at 48 h.For red loam<brown soil<aquic soil<black soil<paddy soil,the correlation coefficients of the five soils were directly proportional to the adsorption capacity,and the larger the correlation coefficient was,the larger the adsorption capacity was.Freundlich model can well fit the adsorption characteristics of fluensulfone in five soils.Except red soil,the 1/n values of black soil,brown soil,aquic soil and paddy soil are all less than 1,indicating that there are favorable conditions for the adsorption of fluensulfone in these four soils.Pearson correlation analysis showed that there was a significant positive correlation between adsorption capacity and organic matter content in each soil（P<0.05）.In the thin layer chromatography experiment,the specific shift values of fluensulfone in black soil,red loam,brown soil,moist soil and paddy soil are 0.42,all less than 0.65,indicating that fluensulfone belongs to the medium mobile pesticide,which is consistent with the above conclusion that fluensulfone is difficult to adsorb in soil,and it has a high possibility to pollute groundwater through runoff and other ways.