The Migration And Transformation Of Typical Pyrethroids In Bohai Coastal Environment

In this study, three typical pyrethroid insecticides, deltamethrin, cypermethrin and fenpropathrin were chosen as the study objects. The behaviors of adsorption, chemical degradation and biological degradation of them in Bohai coastal zone were investigated with gas chromatography and gas chromatography- mass spectrometry. The effects of additional short chain carbon sources and chemical reducing agent on the anoxic degradation of the pyrethroids in sediment of Bohai Sea were also studied.The results show that, the behaviors of single adsorption and mixed adsorption of the pyrethroids on the coastal sediments match pseudo-second-order kinetics and the chemical adsorption plays a major role. In the single adsorption, deltamethrin is most easily adsorbed, cypermethrin is the second, and fenpropathrin is the last. Competition happens in the mixed adsorption of three pyrethroids on the coastal sediments. The adsorptions include surface adsorption and distributional effects.The anoxic degradation kinetics of the pyrethroids in sediment of Bohai Sea match pseudo-first-order kinetics no matter they exist separately or mixedly. When the pyrethroids coexist in the coastal sediment, the biological degradation plays a major role, while chemical degradation plays a minor role. The existence of fenpropathrin can promote the degradations of. cypermethrin and deltamethrin. But the coexistence of cypermethrin and deltamethrin inhibits the mutual degradation.With the addition of appropriate concentration of glucose and sodium acetate, the anoxic degradations of three pyrethroids are promoted effectively. Without the additional carbon sources, FeSO4·7H2O restrains the anoxic degradation of fenpropathrin, cypermethrin and deltamethrin in sediment of Bohai sea. With the existence of glueose and sodium acetate, FeSO₄·7H₂O promotes the anoxic gradation of fenpropathrin obviously in sediment of Bohai Sea, but the effects of FeSO₄·7H₂O on cypermethrin and deltamethrin's degradation are small relatively, which is due to the different molecular structures of cypermethrin and deltamethrin.