HR: 0800h
AN: A51A-0029    [Abstracts]
TI: Atmospheric Aging of Semi-volatile Pesticides: Real Time Monitoring of Cypermethrin Photo- oxidation Using FTIR
AU: * Segal-Rosenheimer, M
EM: segalm@tx.technion.ac.il
AF: Department of Civil and Environmental Engineering, Technion - Isreal Institute of Technology, Technion City, Haifa, 32000, Israel
AU: Dobuwski, Y
EM: yaeld@tx.technion.ac.il
AF: Department of Civil and Environmental Engineering, Technion - Isreal Institute of Technology, Technion City, Haifa, 32000, Israel
AB: Pesticides are highly toxic compounds that unlike other pollutants are intentionally introduced, in large quantities, to the environment. The vast majority of them are applied to agricultural lands, but they are also widely used in urban areas as herbicides, insecticides and fungicides. Pesticides may be promoted into the atmosphere during their application via drift of aerosols, as well as by volatilization or dust erosion from treated surfaces after application. In the atmosphere, semi-volatile pesticides may remain as pure aerosols or become adsorbed upon background aerosols or surfaces. During transport or as deposited thin films, they undergo chemical degradation processes due to interaction with atmospheric oxidants and/or solar radiation. Although previous studies indicate that a major portion of applied pesticides wind up in the atmosphere, this is the medium about which we know the least regarding pesticides' fate. Quantitative data regarding aging processes of these hazard air pollutants are important in order to asses their environmental fate and impact. The present study investigates the heterogeneous reaction of thin film of cypermethrin, a common used insecticide, with atmospheric ozone and UV radiation. The reactions are monitored in real time using novel apparatus that combines ATR/FTIR and Long-path IR gas cell for examining the condensed and gas phases, respectively. The obtained data, including oxidation rate constants and photochemical quantum yields, are used to determine atmospheric lifetime of cypermethrin and its probability to reach non-target regions. Kinetic results from the oxidation of cypermethrin with different concentrations of ozone show that its atmospheric half-life time, with regard to ozone, is in the same order of magnitude as other known degradation processes in the soil and water compartments. Also is shown that some of the condensed phase products are more water soluble than the parent molecule, hence having higher potential to be more mobile in soil and to reach groundwater. The main gas-product detected was phosgene, which is a nerve gas. This might raise a question of using cypermethrin as an indoor insecticide (as currently done), especially in poorly ventilated environments. Solar radiation was shown to have a large effect on cypermethrin with half life of only several days. Some of the condensed photo-degradation products were similar to the ozonation ones and hence, are assumed to have the same environmental impact. Photo-degradation gas products were found to be carbon dioxide, carbon monoxide and formic acid, which after their formation may participate in additional atmospheric reactions. Thus, the present results suggest that photolysis plays a dominant role in cypermethrin's outdoor environmental fate, while ozonolysis plays a larger role indoors. In both cases, some of the degradation products are toxic and are likely to further pose an environmental risk that needs to be considered.
DE: 0317 Chemical kinetic and photochemical properties
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting