Submitted to: Proceedings of American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2005
Publication Date: 9/1/2005
Citation: Potter, T.L., Manning, T., Folsom, D., Hardin, L., Wauchope, R.D. 2005. Tebuconazole ozonation in water: by-products and dissipation kinetics [abstract, oral presentation]. The 230th American Chemical Society National Meeting. Washington, DC. 209C oral. Interpretive Summary:
Technical Abstract: Oxidative destruction of pesticides with ozone has significant potential as a treatment technology. Complete removal and or substantial reduction of pesticide residues in raw drinking water, wastewater, soil, and on surfaces of fruits and vegetables have been reported; however, predicting the extent and efficacy of treatment remains difficult. Reaction rates with ozone and by-product formation have been reported for only a small fraction of the hundreds of pesticide active ingredients in use. In this study we examined the reaction kinetics of the triazole fungicide tebuconazole with ozone by monitoring dissipation of the parent and accumulation and decay of reaction by-products in distilled-deionized water and well water by HPLC-APCI-MSn. Dissipation data were well described by pseudo-first order kinetics (r2=0.977 to 0.999) with the rate constant increasing about 10X as the pH was increased from 3 to 9. Fourteen by-products were identified whose structures suggested two degradation pathways; initial cleavage of the compound’s t-butyl group or oxidation of its chlorophenyl ring. The later was predominant. The principal by-product accounting >50% of all products was presumably derived by complete oxidation of chlorophenyl group to yield a '-hydoxy acid that subsequently cyclized to produce a '-lactone. This is the same compound that was recently described as the principal product of tebuconazole aerobic soil metabolism. Results show that ozonation may effectively remove tebuconazole from water inadvertently contaminated by tebuconazole. However relatively stable by-products were formed. Their complete destruction requires further investigation.