سميت و پايداري باقيمانده توكسافن در خاك

Persistence and Toxicity of Toxaphene residues in Soil

Introduction: Toxaphene is a persistent chlorinated hydrocarbon insecticide which can bioaccumulate in foodweb and cause serious public health and environmental problems. The technical mixture of toxaphene contains over 800 different congeners with different toxicity and resistance to degradation. This study was carried out to determine the toxicity of toxaphene residues from soil on housefly and the persistence of toxaphene in soil. Methods: Toxaphene residues were extracted from soil samples taken on zero day, 60 days, 1 year, 2 years and 3 years following field application of toxaphene and analyzed by using a gas_ liquid chromatography. Then their toxicity as topical lethal doses for 50 percent of the animals (LD50 Values) were determined in houseflies. Results: Field soil with an orginal Toxaphene residue of 7.1 ppm declined to about 3.5 ppm after 3 years. The ratio of the LD50 (lethal dose for 50 percent of the animal) of zero day, 60 day, 1 year, 2 year and 3 year soil reidues to the LD50 of of technical toxaphene were 1.07, 1.11, 1.23, 1.31 and 1.36. Discussion: The results obtained clarify that the degradation and detoxification of this pesticide in soil is very slow and that toxic components my persist for long period of time.