Sarah Epstein’s (’20) Senior Research

Sarah Epstein (’20) presented her Independent Study project entitled “Pesticides in the Atmosphere: The Heterogeneous Ozonolysis of Triticonazole” at The College of Wooster’s Senior Research Symposium. Her presentation is the manifestation of countless hours of research, collaboration, and creative expression.

Pesticides are an emerging environmental concern as they are widely used across the globe to help farmers eradicate pests, weeds, and other unwanted organisms that may harm their crops. This present study examined the heterogeneous ozonolysis of triticonazole, a broad-spectrum fungicide, by conducting the ozonolysis degradation and monitoring the reaction using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, determining the reaction kinetics and rate constants through RStudio analysis, and characterizing the degradation products using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). The second order rate constant appeared dependent on ozone concentration; k2 = (8 ± 1) x 10-17 cm3 ⋅ molecule-1 ⋅ s-1 at ~ 400 ppb of ozone, and k2 = (3.54 ± 0.06) x 10-17 cm3 ⋅ molecule-1 ⋅ s-1 at ~850 ppb of ozone which indicated that the reaction mechanism and pathway potentially changed when exposed to low versus high ozone concentration. The characteristic lifetime of triticonazole was determined to persist in the atmosphere due to heterogeneous ozonolysis for 6.9 – 9.5 hours under pristine atmospheric conditions, and for 41-57 min under polluted atmospheric conditions, which compared to other triazole fungicides was not long at all. Using reverse phase chromatography, positive mode LC-QTOF-MS, and analyzing the data with Qualitative Analysis, 20 potential products were found by their retention time, m/z value, and proposed chemical formula (if applicable). However, in silico mass spectral analysis methods must be performed to generate molecular structures and formulas of the degradation products to understand the atmospheric implications of the heterogeneous ozonolysis of triticonazole.