Use of Stable Tracer Studies To Evaluate Pesticide Photolysis at Elevated Temperatures
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- 作者：Vincent R. Hebert ; Cindy Hoonhout ; and Glenn C. Miller
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2000
- 出版时间：May 2000
- 年：2000
- 卷：48
- 期：5
- 页码：1916 - 1921
- 全文大小：85K
- 年卷期：v.48,no.5(May 2000)
- ISSN：1520-5118
文摘
New methods were developed to determine photolysis rates of medium-weight pesticides in the gasphase using elevated air temperatures and solid-phase microextraction (SPME). A 57-L glasschamber was constructed that utilized collimated xenon arc irradiation that could heat chamberair to increase the amount of pesticide in the gas phase. Gas-phase photolysis rates were determinedat various air temperatures by comparing the rate of loss of each of the tested pesticides to aphotochemically stable tracer, hexachlorobenzene. Interval sampling of gas-phase constituents wasperformed using SPME immediately followed by GC-ECD or GC-MSD analysis. The two pesticidesunder examination were the dinitroaniline herbicide trifluralin and the organophosphorus insecticidechlorpyrifos. The gas-phase photolysis for trifluralin was found to be rapid with half-lives of 22-24min corrected for sunlight. These results were comparable to photochemical lifetime estimates fromother investigators under sunlight conditions. Elevating temperatures from 60 to 80 
C did notaffect photolysis rates, and these rates could be extrapolated to environmental temperatures. From60 to 80 C, gas-phase chlorpyrifos photolysis lifetimes were observed to range from 1.4 to 2.2 hcorrected for sunlight and will thus be important together with hydroxyl radical reactions forremoving this substance from the atmosphere. At these elevated temperatures, pesticides and tracercompounds were found to be substantially in the gas phase, and possible effects on reaction ratesfrom wall interactions were minimized.Keywords: Photolysis; pesticide; SPME; atmosphere
C did notaffect photolysis rates, and these rates could be extrapolated to environmental temperatures. From60 to 80 C, gas-phase chlorpyrifos photolysis lifetimes were observed to range from 1.4 to 2.2 hcorrected for sunlight and will thus be important together with hydroxyl radical reactions forremoving this substance from the atmosphere. At these elevated temperatures, pesticides and tracercompounds were found to be substantially in the gas phase, and possible effects on reaction ratesfrom wall interactions were minimized.Keywords: Photolysis; pesticide; SPME; atmosphere