Wintertime Distributed Ozone Measurement in Utah's Uintah Basin during UBWOS 2012
Abstract
Recent wintertime measurements in two basins in the Rocky Mountains with significant fossil fuel production have revealed serious air quality concerns with respect to ozone (O3). Wintertime O3 levels greater than the current National Ambient Air Quality Standard (NAAQS) of 75 ppbv, expressed as a daily maximum 8-hr average, were observed first in the Upper Green River Basin of western Wyoming in 2005 and then in the Uintah Basin of eastern Utah in early 2010. This abstract reports on a part of the Uintah Basin Winter Ozone 2012 Study (UBWOS 2012) designed to better understand the temporal and spatial extents of elevated O3 in the Basin. A prior study in the Basin during winter 2010/2011 investigated the temporal and spatial extent of O3. Ten monitoring sites were setup throughout the Basin using 2B Technology 205 Ozone Monitors; data from six other monitoring sites around the Basin were also gathered. Hourly averaged O3 over 120 ppbv were recorded in many locations. Levels above the 75 ppbv 8-hr NAAQS were observed at 14 of the 16 sites, with 11 sites logging more than 3 exceedences. Two sites recorded 25 exceedences. The highest O3 and greatest number of exceedences occurred in areas with the greatest fossil fuel production density. Elevated O3 was also found in population centers but with a different diurnal pattern due to local sources. The follow-on study conducted during winter 2011/2012 expanded the number of ozone monitoring sites to 30 to provide better spatial coverage; 19 were operated by the investigators and 11 were operated by other groups. In contrast to the previous study, no elevated O3 levels were recorded at any location. The highest 1-hr O3 level observed was 65.8 ppbv and the highest 8-hr average level was 62.9 ppbv. The most significant difference between the two winters was the weather - winter 2010/2011 had snow cover from December through mid-March and experienced 6+ multi-day temperature inversion periods, while winter 2011/2012 had very little snow cover and did not experience any significant multi-day temperature inversion periods. Studies in Wyoming list snow cover and persistent ground-based temperature inversions as two key factors leading to elevated wintertime O3. Daily maximum O3 levels throughout the Basin were spatially consistent. Maximum O3 increased from 35-45 ppbv in early January to 55-65 ppbv in mid-March, which is likely tied to increasing solar radiation. Population center sites exhibited the highest diurnal variation of all sites with differences between daily maximums and minimums usually greater than 30 ppbv. Low elevation rural sites showed a diurnal pattern similar to but slightly lower in magnitude than that observed in population centers. Significant early morning decreases in O3 at these low elevation rural sites were delayed by ~24 hours after a mixing event compared to the population centers. Higher elevation sites along the northern and southern fringes of the Basin exhibited diurnal patterns with 5-10 ppbv differences between daily maximums and minimums, indicative of measurements of free tropospheric O3 rather than ozone influenced by activities in the Basin.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A23B0224M
- Keywords:
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- 0365 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: composition and chemistry