Degradation of Endosulfan I and Endosulfan II in the Aquatic Environment: A Proposed Enzymatic Kinetic Model that takes into account Adsorption/Desorption of the Pesticide by Colloidal and/or Sediment Particles
The rate of degradation of the α and β isomers of endosulfan, endosulfan I and endosulfan II in distilled water and river water containing river sediment, were investigated over a period of 90 days. An immediate loss of 18 % endosulfan I and 22 % endosulfan II from the water phase of the river water containing river sediment was observed as a result of adsorption by the sediment. Subsequently biphasic linear rates of degradation were observed for both endosulfan I and II in the water phase, as well as the sediment phase of the experiment. Minimal degradation was observed in the distilled water control. An enzymatic kinetic model is presented showing that the biphasic linear rates are consistent with microbial degradation of free and colloidal particle-adsorbed pesticide in the water phase, and colloidal particle- and sediment particle-adsorbed pesticide in the sediment phase of the experiment. The estimation of the biphasic rates of degradation of the pesticide in the water and sediment phases of the system, and the factors affecting the rates of degradation, are discussed.
Keywords: Endosulfan, Degradation Kinetics, Aquatic Environment, Pesticide, Adsorption/Desorption Kinetics