Residual Dynamics And Environmental Behavior Of Niclosamide In Lakeshore Grass Soil

Study the residual degradation dynamics and the possible degradation intermediates of molluscicide niclosamide in lakeshore grass soil of Poyang Lake, the law and the mechanism of its natural degradation are analyzed and discussed. Pesticide was applicated by using the actual mode, through site selection and site layout, effects of sunshine, rainfall, soil characteristics, topography and other natural factors to the migration and the natural degradation of niclosamide was studied. Soil samples were collected three consecutive depths, use methanol as the extractant, through ultrasonic extraction-vacuum filtration-evaporative concentration, use high performance liquid chromatography(HPLC) determine niclosamide and its degradation intermediates in soil. Process the experimental data, and draw out the change trends of niclosamide and its degradation intermediates in soil.The experimental results indicate: the migration of niclosamide is reversible and repeatable in soil; In rainy season, rainfall makes a great effect on migration of niclosamide in soil; In dry season, The moisture content of soil becomes the main limiting factor to the migration of niclosamide; The leaching of rainfall can effectively remove the residue of niclosamide in soil; Strong sunshine restricts the degradation of niclosamide in soil through restraining the activity of microbial; Environment like uncovered sandy soil of low biomass or soil that is lack of water circulation is not conducive to the remove of niclosamide; Niclosamide can be hydrolyzed into 2-Chloro-4-nitroaniline and 5-Chlorosalicylic acid, 5-Chlorosalicylic acid can be converted to 2,5-Dihydroxybenzoic acid, but 2-Chloro-4-nitroaniline is difficult to be converted to 2-Chloro-4-nitrophenol under natural environment.