Characterization and Nonparametric Regression of Rural and Urban Coarse Particulate Matter Mass Concentrations in Northeastern Colorado

The Colorado Coarse Rural Urban Sources and Health study (CCRUSH) is an ongoing study of the relationship between coarse particulate mass concentrations (PM10–2.5, particulate matter with diameter between 2.5 and 10 μm) and selected health effects. For two urban monitoring sites in Denver, CO, and two comparatively rural sites in Greeley, CO, hourly mass concentrations of PM10–2.5 and fine particulate matter (PM2.5, diameter less than 2.5 μm) have been measured by using dichotomous tapered element oscillating microbalances (TEOMs) with Filter Dynamics Measurement Systems (FDMS). This paper presents air quality results from just over a year of PM2.5 and PM10–2.5 measurements. Average PM2.5 concentrations ranged from 7.7 to 9.2 μg m−3 across the four sites with higher concentrations in Denver than Greeley. Average PM10–2.5 concentrations ranged from 9.0 to 15.5 μg m−3 with the highest values at the site in northeast Denver. Temporal variability in PM10–2.5 was higher than that in PM2.5 concentrations at all four sites. The two Greeley sites displayed moderate spatial correlation for PM2.5 and high correlation for PM10–2.5, whereas the two Denver sites showed lower spatial correlation for both PM sizes. PM10–2.5 concentrations in Denver were highest with winds from the direction of the city's urban core. PM10–2.5 concentrations in Greeley were moderately elevated with winds from the southwest to the northwest, coming from Denver and other large Front Range communities. Wind speed regressions for PM10–2.5 at the Denver sites primarily exhibited resuspension effects, while PM10–2.5 concentrations in Greeley showed relatively complex wind speed dependence.