Degradation Kinetics of Some Organophosphorus Insecticides in Aksu River, Antalya

Abstract

The degradations of four organophosphorus insecticides were determined in water samples collected from the Aksu river in Antalya region in Turkey in April 2002. Water samples were spiked with an initial concentration of 50 μg/L of pesticides chlorpyrifos, azinphosethyl, phorate and ethion. The effects of temperature, adsorption, biodegradation, photo degradation and volatilization to the degradation of pesticides in real Aksu river water were investigated over 8 week period. The degradation kinetics was monitored in closed bottles stored in dark at three different temperatures (T = 10, 25 and 40°C) and in a system exposed to natural sunlight (at variable temperature). Aksu river water samples had been conditioned to each parameter before addition of the known amount of insecticides. For the identification of the insecticides, liquid-liquid extraction with dichloromethane followed by GCNPD was used. Half-lives of the insecticides were determined for each parameter. It was observed that half-lives of insecticides are varying depending on the environmental conditions. It was determined that the most effective way for degradation of azinphos-ethyl and ethion is photodegradation. Biodegradation and adsorption were significantly effective on degradation of chlorpyrifos. Phorate was found to be the fastest degrading insecticide under all circumstances.