Ecological Toxicology Studies Of Mesotrione On Soil Microorganism And Earthworm (Eisenia Fetida)

Mesotrione is a triketones herbicide that is mainly used in corn fields to control the broad-leaved weeds.The herbicide is weak acid.Its aqueous solution has strong stability,difficult to photolysis,volatile,and other herbicides have certain physical compatibility,developed a hybrid preparations,and widely use.The improper use of herbicides or long-term a large number of repeated use,can cause harm to the ecological environment of the soil.To evaluate the safety of mesotrione on the soil environment,studies were conducted concerning its influences on soil enzymes and soil microorganisms by conventional physiological and biochemical methods and combining with the terminal restriction fragment length polymorphism(T-RFLP),RT-PCR.In addition,the oxidative stress and DNA damage in the earthworm Eisenia fetida induced by mesotrione were also investigated.The main results were summarized as follows:1?In this studies,using plate count method to determine the different concentrations of mesotrione on the number of microorganisms in the soil.Results show that the number of soil bacteria,fungi and actinomycetes in the 0.1,1.0 and 5.0mg/kg mesotrione treated soil were inhibited than those in the control groups at 20 d,With the incubation time prolonged,the number of bacteria actinomycetes were gradually returned the control levels at 20 d,but the number of fungi were inhibited.On the whole,the experiment set under the concentration of methyl ketone sulfone grass on the soil microbial toxicity is small.2?In this studies,effect of mesotrione on soil enzyme activities under the laboratory simulation conditions was investigated.Three enzymes,i.e.,Urease,acid phosphatase,?-glycosidase,were selected.The results found that the activities of ureas in the 0.1 and 1.0mg/kg mesotrione treated soil were higher after inhibited than those in the control groups.the activities of ureas in the 5.0mg/kg mesotrione treated soil were inhibited than those in the control groups.But the activities of ureas were returned the control levels at 20 d.The activities of acid phosphatase in the 0.1mg/kg mesotrione treated soil were inhibited than those in the control groups at 2d,but it were gradually higher.The activities of acid phosphatase in the 5.0mg/kg mesotrione treated soil were higher than those in the control groups at 5d,but it were gradually inhibited.The activities of ?-glycosidase in mesotrione treated soil were higher after inhibited than those in the control groups,but it were gradually returned the control levels at 20 d.3?Toxic effects of mesotrione on the diversity of soil microbial community structure were evaluated through T-RFLP methods.The present results indicated that mesotrione change the dominant structure of the soil microbial community,but the diversity of the soil microbial community structure were decreased by the mesotrione and the banlance were disturbed.4?The results of RT-PCR indicate that in addition to the processing of 0.1mg/kg group in 5days mesotrione has a promoting effect on AOB-amoA,the copy number of AOA-amoA gene and AOB-amoA gene were decreased by the rest of concentration of mesotrione at different concentrations,and this inhibition have a significant dose-effect relationship.5?Oxidative stress and DNA damage in the earthworm Eisenia fetida induced by mesotrione were investigated in the OECD soil.Compared to the control,the ROS level was higer at the time of treatment;the SOD activity increased on the 14 thd but decreased on the after 14d;the CAT?POD and GST activity increased on the 21 thd but returned the control levels at 20d;the MDA contents were decreased in 0.1mg/kg,others are no difference with the control.the MDA contents were higer at 14 and 21d;it was returned the control levels at 28 d expect 2.5mg/kg;Comet experiment is more sensitive,methyl ketone sulfone grass under the treatment of 28 days,caused the earthworm body cavity of cell DNA damage,and the longer,the greater the concentration,the more serious the damage,and present a significant dose-effect relationship.This study also shows that different kinds of biomarkers of common use,and can correctly evaluate the environmental contaminants the ecological toxicity in soil,provide theoretical support for soil pollution condition monitoring.