Research Of Microbial Combined With Chemical Ways To Degrade Trifluralin In Agricultural Water

Trifluralin is a widely used pesticide in agriculture and fisheries,however it inevitably causes pollution and residual issues.The degradation of pesticides in environment has been a focus of academic research in recent years.The commonly used ways to degradae pesticides include biological,physical and chemical methods.In this research,we studied the dynamics of trifluralin degradation in simulated aquaculture water based on the establishment of a method measuring the content of trifluralin in water.We isolated a strain FJ-01 which was capable of degrading trifluralin in aquaculture water efficiently from the sediment got from shrimp and crab ponds using trifluralin for many years.We focused on cell colony morphology and 16SrDNA sequence analysis of FJ-01.Then the appropriate pH,water temperature,brightness ratio and inoculation were determined.In addition,we selected percarbonate as a chemical oxidant to degrade trifluralin and tried to find out the appropriate dosage and optimal duration of action when it was combined with FJ-01.At last,we used zebrafish as a test organism to see the ecotoxicity of the degradation products of the three different ways to degrade trifluralin in water.The results show that:1.We use gas chromatography to analyze the content of trifluralin in aquaculture water.The detection limit and low limit of the method is 0.15μg·L-1 and 0.42μg·L-1,with the recovery rate of 82.88%-108.19%.This method could be used to accurately monitor the dynamics of trifluralin in aquaculture water.2.trifluralin has some residual effects in water.The half-life of trifluralin in aquaculture water is within 35 days.Initial concentration,water temperature and illumination time are important factors affecting trifluralin degradation.3.The filtered strain FJ-01 is initially identified as Leucobacter sp.based on cell colony morphology and 16SrDNA sequence analysis.4.Considering the actual situation of aquaculture,suitable conditions for Leucobacter sp strain to degrade trifluralin is:pH 6.0～8.5,water temperature 22～30℃,brightness ratio 12:12,inoculation 0.01%when the initial concentration of trifluralin is 0.05mg·L-1.5.Chemical oxidants like percarbonate and oxone have a good chemical degradation effect on trifluralin degradation.The amount 0.15～0.30 mg·L-1 can make the initial concentration of trifluralin at 0.05 mg·L-1 and 0.50 mg·L-1 to degrade efficiently.The degradation rate of is more than 33%.The degradation occurs mainly within 5 hours after contacting with the water body.6.The degradation rate of trifluralin is up to 69.44%~75.87%using 0.01%FJ-01 combined with 0.15 mg·L-1 percarbonate within 5 days.The degradation effect is significantly better than single microbial degradation or chemical oxidation.7.Ecotoxicity test shows that the three ways(microbial,chemical and microbial combined with chemical ways)to degrade trifluralin in water cause no death of the tested fish.What’s more,the fish shows no abnormal behavior or morphological changes,which indicates that the degradation process does not have acute or subacute toxic effects on fish.8.The dynamic changes of SOD and MDA in fish muscle shows that the degradation process of the three different ways causes no significant oxidative damage to the tested fish since there is no significant changes in SOD and MDA of fish.Studies have shown that microbial combined with chemical ways to degrade trifluralin is an efficient way.It can open up a new way for the degradation of pesticides in water.