Degradation Dynamics Of Three Kinds Of Commonly Used Fungicides In Wheat Fields And Their Toxicity To Soil Microorganisms

Effects of pesticides on soil microbial respiration has become an important index to evaluate the safety of pesticides on the ecological environment. Wheat is the main grain crop in Shandong province. In the whole growth period, wheat has many kinds of diseases. Such as wheat sheath blight, powdery mildew and rust, wheat scab and so on. It is still the main measures to control the above diseases by using fungicides. Due to the relatively few studies of effects of wheat fungicides on soil microorganism in the wheat field. This study selected 3 kinds of fungicides is widely used in the production:carbendazim, tebuconazole, and difenoconazole? Determination of 3 kinds of fungicides on 2 kinds of soil (high level yield field, middle level field soil) with CO2 absorption method respiration, and determine the level of toxicity of 3 kinds of fungicides on microbial degradation, meanwhile analysis of 3 kinds of fungicides in the soil with high level efficiency liquid chromatography, safety evaluation of 3 kinds of fungicides on the environment. The main results are as follows:1. The effects of 3 fungicides on soil microbial respiration in 2 wheat fields (high level yield field, middle level field) were determined by CO2 absorption method. The results showed that tebuconazole is to promote the effect on microbial respiration,100 mg/kg concentration treatment showed the phenomenon of inhibition after stimulation. The effect of difenoconazole on microbial respiration was low concentration promoted respiration and high level concentration inhibited respiration. Carbendazim respiration of microorganisms in general is inhibited, and the low concentration inhibit respiration on the first stage and then promoting respiration. According to the national standard, three kinds of fungicides are low toxicity to soil microorganism. Toxicity comparison result were:Carbendazim> Difenoconazole> Tebuconazole.2. A residue analytical method was set up for analysis tebuconazole in soil. The residues of tebuconazole in soil was detected by high performance liquid chromatography(HPLC) with Ultraviolet absorption detector(UV). The adoption of acetonitrile/water=75/25 (V/V) as mobile phase, UV detector to 225 nm were measured. The recovery rates of 1 mg/kg,10 mg/kg,100 mg/kg three concentration of tebuconazole respectively was 90.51%?95.97%? 100.85%. Coefficient of variation respectively 1.61,5.56,3.54.3. Study to establish a method for determination of difenoconazole content of HPLC in soil.The methanol/water=85/15 (V/V) as mobile phase, using Agilent Zorbax sb-c18 liquid phase chromatographic column separation, UV detector to 235 nm were measured. The recovery rates of 1 mg/kg,10 mg/kg,100 mg/kg three concentration of difenoconazole were 88.90% 90.39% and 91.08%, coefficient of variation for 4.39,4.94,3.21.4. Study to establish a method for determination of carbendazim content of HPLC in soil.The methanol/water=65/35 (V/V) as mobile phase, using Agilent Zorbax sb-c18 liquid phase chromatographic column separation, UV detector to 282 nm were measured. The recovery rates of 1 mg/kg,10 mg/kg,100 mg/kg three concentration of carbendazim were 87.13%?94.95%?95.21%, coefficient of variation for 3.75,5.50,4.71.5. The three fungicides are arranged according to the dissolution rate of the soil is carbendazim> Tebuconazole> Difenoconazole.The results of the study will lay a good foundation for the rational use of these three fungicides.