Multi-Pollutant Concentration Patterns of Poor Air Quality Poster
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(Previously cleared.) Recent changes in source emissions and concentration patterns of air quality indicators include declines in nationwide emissions of sulfur dioxide and nitrogen oxides, increases in wildland fire emissions and atmospheric ammonia concentrations, fluctuations in intercontinental transport of ozone precursor emissions, compression of the national ozone concentration distribution, and shifts in the season of highest concentration for both ozone and particulate matter with diameter smaller than 2.5 micrometers (PM2.5). We examine the impacts of these changes on the relative abundance of air pollutant concentrations as a function of season and airshed at times and locations with poor air quality. Air quality indicators like PM2.5, ozone, and nitrogen oxides are always present as part of a multi-pollutant mixture. For example, we identify at least 10 geographically diverse airsheds that include monitors reporting greater than 90th percentile concentration for at least 3 well-established air quality indicators. We further evaluate national air quality monitoring network data, including pollutant concentrations as well as diagnostic ratios between indicators from these airsheds on their poorest air quality days. We investigate: 1) what are the strongest associations between air quality indicators for each season and airshed and what factors influence their relationship? 2) how consistent is the relative abundance of air quality indicators within and across seasons and airsheds, and what factors influence this consistency? 3) how many readily recognizable patterns of relative abundance are there across seasons and airsheds, and when and where are they most likely? The overall objective is the practical identification of a set of consistent multi-pollutant concentration profiles representative of current air pollution characteristics, and a quantitative assessment of their frequency and consistency within and across seasons and airsheds. The views expressed are those of the authors and do not necessarily reflect the views or policies of the EPA.