Articles | Volume 16, issue 11
Research article
15 Jun 2016
Research article |  | 15 Jun 2016

Comparisons of urban and rural PM10−2.5 and PM2.5 mass concentrations and semi-volatile fractions in northeastern Colorado

Nicholas Clements, Michael P. Hannigan, Shelly L. Miller, Jennifer L. Peel, and Jana B. Milford

Abstract. Coarse (PM10−2.5) and fine (PM2.5) particulate matter in the atmosphere adversely affect human health and influence climate. While PM2.5 is relatively well studied, less is known about the sources and fate of PM10−2.5. The Colorado Coarse Rural-Urban Sources and Health (CCRUSH) study measured PM10−2.5 and PM2.5 mass concentrations, as well as the fraction of semi-volatile material (SVM) in each size regime (SVM2.5, SVM10−2.5), from 2009 to early 2012 in Denver and comparatively rural Greeley, Colorado. Agricultural operations east of Greeley appear to have contributed to the peak PM10−2.5 concentrations there, but concentrations were generally lower in Greeley than in Denver. Traffic-influenced sites in Denver had PM10−2.5 concentrations that averaged from 14.6 to 19.7 µg m−3 and mean PM10−2.5 ∕ PM10 ratios of 0.56 to 0.70, higher than at residential sites in Denver or Greeley. PM10−2.5 concentrations were more temporally variable than PM2.5 concentrations. Concentrations of the two pollutants were not correlated. Spatial correlations of daily averaged PM10−2.5 concentrations ranged from 0.59 to 0.62 for pairs of sites in Denver and from 0.47 to 0.70 between Denver and Greeley. Compared to PM10−2.5, concentrations of PM2.5 were more correlated across sites within Denver and less correlated between Denver and Greeley. PM10−2.5 concentrations were highest during the summer and early fall, while PM2.5 and SVM2.5 concentrations peaked in winter during periodic multi-day inversions. SVM10−2.5 concentrations were low at all sites. Diurnal peaks in PM10−2.5 and PM2.5 concentrations corresponded to morning and afternoon peaks of traffic activity, and were enhanced by boundary layer dynamics. SVM2.5 concentrations peaked around noon on both weekdays and weekends. PM10−2.5 concentrations at sites located near highways generally increased with wind speeds above about 3 m s−1. Little wind speed dependence was observed for the residential sites in Denver and Greeley. The mass concentration data reported here are being used in ongoing epidemiologic studies for PM in northeastern Colorado.

Short summary
Coarse and fine particulate matter were monitored in Denver and Greeley, Colorado from 2009 to early 2012 as part of the Colorado Coarse Rural-Urban Sources and Health (CCRUSH) study. The study assessed spatial and temporal variability of PM10−2.5 and PM2.5, relationships between pollutants and meteorology, and source patterns in urban and rural environments in semi-arid northeastern Colorado. In future studies, health impacts of PM10−2.5 in urban and rural Colorado communities will be assessed.
Final-revised paper