Effects Of Urea On The Adsorption Of Sulfonlurea Herbicides On Three Kinds Of Minerals And The Interaction Between Sulfonlurea Herbicides And Catalase

Chlorsulfuron,metsulfuron-methyl and bensulfuron-methyl,the most important sulfonlurea herbicides,which are widely used in China,are widely used for controlling grasses,broadleaf and brush weeds in crops.The rate of degradation of them in soil is strongly dependent upon pH,moisture content,temperature of the soil and so on. Residue of them in soil can significantly influence the growth rates of some crops,and even do great harm to next crops.Adsorption of sulfonlurea herbicides by soil minerals and effects of urea,interaction between sulfonlurea herbicides and catalase and phytotoxicity of the sulfonlurea herbicides to next crops were studied by high pressure liquid chromatography(HPLC),batch,fluorescence spectroscopy,fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),atomic force microscope(AFM) etc.These studies have important significances in theory field and practice for probe into environment action of sulfonlurea herbicides in soil,as well as for degrading the harm of the residue of sulfonlurea herbicides in soil to next crops.Some main results and progressions are illustrated as follows:1.The adsorption of sulfonylurea herbicides by kaolinite,goethite,amorphous alumina and the effects of urea on the adsorption were examined with equilibrium adsorption method.The results indicated that the adsorption was according to the Langmuir equation,the maximum absorbing capacities were that amorphous alumina＞goethite＞kaolinite,the maximum absorbing capacities for three kind of sulfonylurea herbicides in the same minerals were that chlorsulfuron＞metsulfuron-methyle＞bensulfulon-methyl.When urea was used,the absorbing capacities on the goethite and amorphous alumina decreased by all different order of urea used;but increased on the kaolinite,especially by adding urea with sulfonylurea herbicides simultaneously.The results studied by FTIR,XRD,TG and AFM showed that compounds of the sulfonylurea herbicides binding respectively with urea will be formed when three sulfonylurea herbicides used respectively with urea simultaneously.2.FTIR spectroscopy was applied to investigate the interaction of Sulfonlurea herbicides and urea.It was shown that sulfonlurea herbicides and urea form compounds through hydrogen bind between the C=O,O=S=O and N-H,and compounds exist in the more polar conformation,which make the solubility of sulfonlurea herbicides bigger,and sulfonlurea herbicides do good to action of herbicide and do great harm to next crops.3.The binding of sulfonlyurea herbicides to CAT and effects of urea in aqueous were studied using fluorescence spectroscopy and UV-vis absorption spectroscopy.It was shown that herbicides have a strong ability to quench the CAT fluorescence mainly through a static quenching procedure.The binding constant K and the number of binding site n were calculated according to the flurescence quenching results.For clorsufuron, K=8.69×10⁵ L·mol^-1 and n=1.16;for metsufuron methyl,K=1.01×10⁶ L·mol^-1 and n=1.20, for bensulfulon-methyl,K=3.52×10⁶ and n=0.77.Based on the mechanism of energy transfer,the distances between accepter herbicide and CAT were obtained.The distance r(clorsufuron)=5.60nm,r(metsufuron methyl)=4.26nm and r(bensulfulon methyl)=3.95nm.It is clear that the binding of metsufuron methyl with catalase is stronger than that of clorsufuron and bensulfulon methyl stronger than that of metsufuron methyl.It is inferred that binding site between herbicides and CAT was Tyr-214.After interaction between herbicides and CAT,the hebicides don't influence on the activity of CAT;on the contrary,the CAT make herbicides be easily adsorbed by plants and make the interaction between herbicides and acceptor stronger.4.The toxicity of the clorsufuron,metsufuron methyl and bensulfuron methyl to next crops were tested by average length using rap e(Brassica juncea).Results showed that the concentration of herbicides and urea,the pH of buffer,and the average root length of rape conform to equations,for clorsufuron y=6.30929-0.07049x₁-0.128379x₂ -0.33333x₃(R²=0.9968),for metsufuron methyl y=18.37279-0.22005x₁-0.29842x₂ -1.47667x₃(R²=0.9951),for bensulfuron methyl y=7.29809-0.10970x₁-0.10179x₂-0.05500x₃(R²=0.9978),and greater of the concentration of sulfonlyurea herbicides,urea and the pH,shorter of the average root length of rape,sulfonlyurea herbicides do greater harm to next crops.