Degradation Of Octachlorodipropyl Ether(S-421) In Tea

Because of its low price and high efficiency,octachlorodipropyl ether(S-421)is widely used as the synergist of carbamates,organic chlorine insecticides and pyrethroids.At present, the S-421 in our country is still widely used in mosquito coils and other household insecticide products.Some studies showed that S-421 widely exists in the environment and agricultural products.However,the fate and degradation of S-421 in the ecological environment are rare known.This article presents the degradation of S-421 in tea by heating and radiation,and the residues of S-421 in tea under field conditions.Preliminary results shown that,heating treatment can effectively reduce the residues of S-421 in tea.The longer the treatment or higher the temperature,the betters its degradation efficiency.The degradation rate for tea polluted with low S-421 concentration(0.3mg kg^-1) reached more than 50%when heating for 1h at 120℃while tea with 6 mg kg^-1S-421 was only 20 percent.However,the degradation rate of the high concentration reached 25～30μg kg^-1min^-1,which is more than 10 times of the low concentration.Irradiation can effectively degradate S-421.The S-421 degradated more than 50%when S-421 solution irradiated by 5 kGy,then degradation did not increase significantly with the radiation dose.Effect of irradiation for degradiation of S-421 in tea was lower than the pure solution,and indicates that tea polyphenols play a role in protection from irradiation degradiation.The S-421 content in fresh leave collected from tea garden without applied any pesticide recently were in the range 0.06-0.089mg kg^-1,and no obvious differences were found between the old leaves and new buds or between species.The results indicated that the S-421 in the tea may mainly come from the atmosphere.