Intra-urban spatial variability of PM2.5-bound carbonaceous components

Mingjie Xie; Teresa L Coons; Steven J Dutton; Jana B Milford; Shelly L Miller; Jennifer L Peel; Sverre Vedal; Michael P Hannigan

doi:10.1016/j.atmosenv.2012.05.041

Intra-urban spatial variability of PM_2.5-bound carbonaceous components

Atmos Environ (1994). 2012 Dec:60:486-494. doi: 10.1016/j.atmosenv.2012.05.041.

Authors

Mingjie Xie¹, Teresa L Coons¹, Steven J Dutton², Jana B Milford¹, Shelly L Miller¹, Jennifer L Peel³, Sverre Vedal⁴, Michael P Hannigan¹

Affiliations

¹ Department of Mechanical Engineering, College of Engineering and Applied Science, University of Colorado, Boulder, CO 80309, USA.
² National Center for Environmental Assessment, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
³ Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO 80523, USA.
⁴ Department of Environmental and Occupational Health Sciences, School of Public Health and Community Medicine, University of Washington, Seattle, WA 98195, USA.

Abstract

The Denver Aerosol Sources and Health (DASH) study was designed to evaluate associations between PM_2.5 species and sources and adverse human health effects. The DASH study generated a five-year (2003-2007) time series of daily speciated PM_2.5 concentration measurements from a single, special-purpose monitoring site in Denver, CO. To evaluate the ability of this site to adequately represent the short term temporal variability of PM_2.5 concentrations in the five county Denver metropolitan area, a one year supplemental set of PM_2.5 samples was collected every sixth day at the original DASH monitoring site and concurrently at three additional sites. Two of the four sites, including the original DASH site, were located in residential areas at least 1.9 km from interstate highways. The other two sites were located within 0.3 km of interstate highways. Concentrations of elemental carbon (EC), organic carbon (OC), and 58 organic molecular markers were measured at each site. To assess spatial variability, site pairs were compared using the Pearson correlation coefficient (r) and coefficient of divergence (COD), a statistic that provides information on the degree of uniformity between monitoring sites. Biweekly co-located samples collected from July 2004 to September 2005 were also analyzed and used to estimate the uncertainty associated with sampling and analytical measurement for each species. In general, the two near-highway sites exhibited higher concentrations of EC, OC, polycyclic aromatic hydrocarbons (PAHs), and steranes than did the more residential sites. Lower spatial heterogeneity based on r and COD was inferred for all carbonaceous species after considering their divergence and lack of perfect correlations in co-located samples. Ratio-ratio plots combined with available gasoline- and diesel-powered motor vehicle emissions profiles for the region suggested a greater impact to high molecular weight (HMW) PAHs from diesel-powered vehicles at the near-highway sites and a more uniformly distributed impact to ambient hopanes from gasoline-powered motor vehicles at all four sites.

Keywords: Co-located samples; Motor vehicle influence; Organic molecular marker; PM2.5; Particulate matter; Spatial variability.

Grants and funding

R01 ES012197/ES/NIEHS NIH HHS/United States