Investigating Ozone Stability: Ogawa Holding Time Experiment in Seattle, WA

Ozone is a naturally occurring gas in the stratosphere. Near to Earth’s surface ozone is toxic in high concentrations and created by chemical reactions between sunlight and automobile emissions such as nitric oxide. Understanding the stability of ozone through Ozone Ogawa samples will improve data analysis of ozone in the environment. Given data on similar experiments assessing the effect of holding times on NO2 samplers, we hypothesized that there would be no significant differences in the measured concentrations for exposed Ozone Ogawa samplers at varying storage times. We investigated the stability of ozone by exposing 18 double sided Ozone Ogawa passive badge samplers to ambient air in Seattle for two weeks. Samplers were hung approximately eight feet from ground level and were protected by a cover to keep samplers dry during exposure. After two weeks, all samplers were retrieved. Four badges were immediately extracted into water and analyzed using ion chromatography (IC). Sixteen of the retrieved badges were immediately stored at 2-4°C, whereas the remaining sixteen badges were extracted into water and stored in vials at 2-4°C for future analysis. After one, two, four, and eight weeks of storage, four exposed Ogawa samplers were extracted and analyzed by IC, along with four of the stored extracts. Our data showed that the differences in average ozone concentrations with time between completion of sampling and extraction are not statistically significant. Therefore, with no significant differences in the measured concentrations, Ozone Ogawa samplers can be safely stored up to eight weeks for analysis.