On average, carbonaceous species made up 77% of the PM2.5
and 66% of the carbonaceous aerosol was OC. Both, OC (r2=0.96)
and EC (r2=0.96) concentrations showed excellent correlation with
PM2.5 concentrations during the study. The large contribution of
carbonaceous species to ambient PM2.5 and the excellent correlations
of OC and EC to PM2.5 suggest that combustion sources are
the dominant contributors to PM2.5. While motor vehicle emissions
are a source of carbonaceous aerosol, the strong correlations of OC
and EC with PM2.5, the stable isotope analysis discussed below and
results from a receptor modeling study (Ancelet et al., 2012)
indicate that residential wood combustion is the dominant source
of the carbonaceous aerosols measured in this study. The highest
TC contributions to PM2.5 concentrations were found on days when
the NES was exceeded or nearly exceeded. On these days, TC made
up 81% of the PM2.5 on average, with a maximum contribution of
89%. The contribution of TC to ambient PM2.5 in this study was
similar to that observed in Libby, Montana (Ward et al., 2011).