A Study On The Sorption Behavior Of Fenvalerate On Marine Sediments

Sorption/desorption of organic pollutants with soil/sediment plays an important role in their transport, fate and bioavailability in natural environment. Sorption and desorption of organic compounds are influenced by such factors as their physico-chemical properties, constituents of sorbents, environmental conditions and coexistent organic compounds. In this thesis, the effects of physical chemical property of sediments, temperature, salinity and pH on sorption of pesticides onto sediments were investigated. The mathematic models of sorption were discussed.It was revealed that there were three stages for the sorption of fenvalerate to sediment. At the first stage there was a fast sorption between the sediment and fenvaleerate. A slow sorption phase occurred between the first to the third hour, followed by a equilibrium of sorption/desorption at the last.It was shown that the sorption isotherms of fenvalerate onto sediments were mainly controlled by the organic contents in sediments. The isotherms can be described very well by linear or Freundlich models, with better fitting results at higher organic contents in sediments. While the sorption isotherms of fenvalerate on sediments can only be described well by Langmuir model at lower organic contents.The conditions of overlying water can affect the sorption behaviors too. The experiment results indicated that temperature was the major factor to affect the sorption behavior of fenvalerate; the sorption capacity of fenvalerate onto sediment was enhanced with decreasing the temperature. The sediment's Kd declined with decreasing pH, which might be a result of the instability of fenvalerate at a higher pH value. It was also shown that the sediment's ability to adsorb fenvalerate was improved by increasing the ion strengthen of the overlying water. The granularity of sediment can also influence the amount of sorption on itself. With decreasing the sediment granularity, its ability to adsorb fenvalerate was increased, owing to the availability of more adsorption surfaces and more organic carbon exposed on the surfaces.