44G-23 |
Studies on the determination of the degradation products and pathways of mancozeb and ethylene thiourea (ETU) by ozone and chlorine dioxide |
E. S. HWANG, Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, 458 Bevier Hall, 905 S. Goodwin Avenue, Urbana, IL 61801 and J. N. Cash, Department of Food Science and Human Nutrition, Michigan State University, 304 G. M. Trout Building, East Lansing, MI 48824. Ozone and chlorine dioxide (ClO2)have been widely used for the oxidation of organic compounds at water treatment plants and were consequently investigated for their capacity to degrade organic pesticides. Use of these compounds is increasing, mainly because they are known to be relatively less toxic and produce fewer disinfection by-products compared to chlorine compounds. The objective of this study was to determine the degradation products of mancozeb and ETU and elucidate the possible degradation pathways in solutions as a result of ozone and ClO2 treatments. This study was developed in a solution at 100 ppm mancozeb and ETU during 60 minutes. Two different oxidizing agents used in this study were (1) ozone @ 3 ppm and (2)ClO2 @ 20 ppm. Degradation products were detected with high resolution GC/MS. The total analysis was combined with rapid gas chromatographic separation and time-of-flight mass spectrometry (TOFMS) with an election ionization source. Mancozeb lead to m/z 144 ion fragmentation, which is 5-imidazoledithiocarboxylic acid, as a major degradation product. ETU showed M+102 which corresponds to its mass, was stable in distilled water and did not undergo hydrolysis during 60 minutes. Ozonation of mancozeb produced ETU as a major product. Treatment of ETU with ozone produced several degradation compounds. From prolonged ozonation, the CS2 or CS group was removed. Although mancozeb and ETU were degraded by ClO2, this oxidant was less effective than ozone at the concentration used in this study. However, it is anticipated that mancozeb and ETU would be completely degraded by the ClO2 treatment if the concentration of ClO2 is increased above the 20 ppm that used in this study. These results suggest that ozone and ClO2 were effective on the degradation of pesticides. Consequently, further studies are required to assess the toxic effects as a results of chemical oxidation.
Session 44G, Toxicology & Safety Evaluation
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