Particulate matter (PM) in Masterton, New Zealand, a rural community with a population of 20 000, was studied
during the winter to gain an understanding of the carbonaceous species and their influence on PM concentrations. The
average PM10 concentration during the winter was 21.0±14.8 μg m–3, of which 64% was PM2.5. PM2.5 concentrations
were found to be the main cause of elevated PM10 concentrations, and were responsible for exceedances of the New
Zealand National Environmental Standard for PM10. Carbonaceous species were 47 and 77% of the total PM10 and
PM2.5, respectively. Organic carbon (OC) concentrations were always higher than elemental carbon (EC) concentrations.
OC and EC concentrations showed excellent correlation with PM2.5 concentrations, suggesting that combustion
processes were the dominant source of PM. Stable isotope analysis yielded δ13C values ranging from –24.9 to –27.6‰,
which is indicative of wood combustion. Analysis of particle–phase PAHs by thermal desorption GC/MS yielded an
average total PAH concentration of 38.9±25.9 ng m–3, accounting for 0.3% of the PM2.5. Analysis of all of the results
revealed that residential wood burning for domestic heating was the main source of PM pollution in Masterton. The
results of this study suggest that a PM10 standard alone, particularly in areas where wood combustion is common, may
not be providing an adequate level of protection for the exposed population.