Study On The Environmental Behavior Of Carbaryl And Residual Dynamics In Paddy Field Envionment

Environmental behavior of pesticides is an important content of safety evaluation of pesticides; pesticides’residue dynamic research is the basis of guide the scientific using pesticide and defining maximum residue limit. Carbaryl is a kind of insecticide, and plays an important role in agricultural production. In this paper, a method for the residue determination of carbaryl was developed and the environmental behavior including photolysis, soil degradation, absorption and leaching of Carbaryl was investigated, aimed to know the environmental fate and the potential hazards of carbaryl, and provid a scientific basis for its rational use.An analytical method for determining Carbaryl residues in paddy water, soil, plant, rice and rice husk was established by using HPLC and GC-MS, detection results showed satisfactory linear relationship and precision. The average recoveries of Carbaryl in different paddy samples spiked at0.05-5.0mg/kg ranged from73.94%to111.25%, with RSD<9.78%. These results indicated that the developed method could be applied for residue determination of Carbaryl.Residues degradation dynamics of Carbaryl in different paddy samples for two years in three places have been carried out. The results indicated that the degradation dynamics in paddy samples all fit the kinetic equation. In2011, the half-lives of degradation of water, soil and straw in Jiangsu, Jiangxi and Tianjin were0.55～0.92d,4.02～12.67d,1.38～2.77d, respectively; and in2012. were0.54～1.43d,1.02～12.60d,1.87-5.66d, respectively. Final residual results showed that the residues of samples were less than the minimum detectable concentrations after28days on the last use of Carbaryl with the recommended amount in paddy field.The photochemical degradation of Carbryl in various solutions and its influencing factors were studied under the irradiation of high-pressure mercury lamp. Results showed that Carbaryl photolysis rate decreased with increasing of initial concentration. The order of photolytic rates of Carbryl in different organic solvents was:n-hexane>methanol> acetonitrile. The photolytic rate of Carbryl in alkaline buffer solution was much faster than in acid and neutral buffer solution. The presence of NO3-,NO2-and SDS all inhibited Carbryl photodegradation rate, and the H2O2could increase the photolysis rates.The half lives of degradation of Carbryl in yellow soil, black soil, paddy soil, red soil were18.24d、24.75d、31.51d、69.31d, respectively. In aerobic, anaerobic and sterilized conditions, the degradation rate in the four soils showed the following sequence:yellow soil> black soil> paddy soil> red soil. The degradation rate was increased with the pH values rising.The adsorption ability of carbaryl in red soil, yellow soil, paddy soil and black soil were different. The adsorption coefficients of these four kinds of soil were0.127,0.381,9.652,15.54, indicated that the adsorption capacity were black soil> paddy soil> yellow soil> red soil. Organic matter content was the main factor that affects the adsorption capacity of carbaryl in the soils, the adsorption capacity was enhanced with the organic matter content increased in soil.The leaching abitity of carbaryl in different soils were studied by TLC and column leaching. Results showed high leaching ability in red soil, medium in yellow soil, and comparatively low in paddy soil and black soil. Organic matter content played the main factor that affects the leaching capacity of carbaryl in the soils, the leaching was weakened with the organic matter content increased in soil.