Study On Environmental Behavior Of Thifensulfuron-methy

Thifensulfuron-methy is a new kind herbicide of sulfonylurea. It is a synthesis inhibitor for side-chain amino acids. It can prevent and wipe out field broadleaf weeds of cereal effectly and is being widely used now. With the extensive use of thifensulfuron-methy, there may be residual in the environment. It may have some influence to biological and environment, even to human health. Thus it is of great practical significance to study the degradation behavior of thifensulfuron-methy in environment for reasonable use of the pesticide in our country and environment and the safety evaluation of ecology.This review have studied the soil degradation, hydrolysis, photolysis, water-sediment degradation of thifensulfuron-methy by simulation test in lab, and got the conclusions as follows:(1) It has established a analytical method of HPLC to determine the residual of thifensulfuron-methy in water, soil and sediment samples. Water samples extracted by dichloromethane, and soil and sediment samples were extracted with acetonitrile. Since the soil and water samples have little impurities, there is no need to purify. While the sediment samples need to be cleaned up by Florence lithium silica chromatographic column. And then detected by Ultraviolet. The spiked recoveries in the samples were in the range of81.32%～99.65%and the RSD range is0.89%～3.21%. Minimum detectable level in standard samples was5.0×10-10g, and the lowest detectable concentration was0.05mg/kg. The results show that the method meets the demands of pesticide residue analysis.(2) The degradation dynamic of thifensulfuron-methy in soils followed the first-order kinetics. The degradation rate of thifensulfuron-methy in the three soils was fluvoaquic soil>paddy field soil>krasnozem, with the corresponding half-lives2.7,5.6,9.8d in aerobic condition, and7.6,11.1,13.7d in the anaerobic, respectively. Soil microorganism and pH was influenced for the degradation of thifensulfuron-methy in soils. In the above two environments, the half-life for degration of thifensulfuron-methy in3different kind soils for trial are both less than30d. According to the standard set by guidelines on environmental safety assessment for chemical pesticides, thifensulfuron-methy is belonged to easily degradable pesticide in soil.(3) Hydrolysis of thifensulfuron-methy in different buffers followed the first-order kinetics. The hydrolysis rate of thifensulfuron-methy in different buffers was pH4> pH9> pH7, with the corresponding half-lives93.67h(3.9d),385.08h (16.05d),2310.45h (96.27d) at25℃, and3.91h,12.31h,103.45 h (4.31d) at50℃, respectively. Temperature and pH was influenced for the hydrolysis of thifensulfuron-methy in different buffers. In this experiment, the half-life is the longest when the tempreature is25℃, pH is7and it is2310.49h(96.27d). According to the standard set by guidelines on environmental safety assessment for chemical pesticides, Thifensulfuron-methy is a kind of herbicide easily hydrolyzed in25℃(pH=4,9) and50℃(pH=4,7,9) buffers, while difficult to hydrolysis in25℃(pH=7) buffers.(4) The photolytic half-life of thifensulfuron-methy in pure water is2.30h and there is almost no degradation in the dark comparision set contemporary. The photolysis rate in illumination is much faster than its degradation in dark. Thifensulfuron-methy is a kind of herbicide easy to photolysis. Soil surface photolysis test in7days shows that its photolysis rate in illumination has no significant differences with that in dark. Thifensulfuron-methy is a kind of herbicide difficult to photolysis in soil surface.(5) The degradation dynamic of thifensulfuron-methy in the water-sediment system followed the first-order kinetics. In aerobic condition, the degradation half-life of thifensulfuron-methy in the West Lake water-sediment system and Canal water-sediment system are12.79d and15.17d. While in anaerobic condition, they are14.87d and17.42d. The degradation rate of thifensulfuron-methy in the West Lake water-sediment system is higher than it in the Canal water-sediment system, and that in the water-sediment system in anaerobic condition is inferior to in aerobic condition. Mcrobial degradation to total degradation ratio is greater in the West Lake water-sediment system than that in the Canal water-sediment system, and it is less in aerobic condition than that in anaerobic condition of the two water-sediment systems. Mcrobial degradation to total degradation ratio is small in the water-sediment system and it is mainly hydrolysis.