Identification of Particulate Matter Sources on an Hourly Time-Scale in a Wood Burning Community

Particulate matter (PM) sources at two different sites in a rural town in New Zealand were investigated on an hourly time-scale. Streaker samplers were used to collect hourly, size-segregated PM_10–2.5 and PM_2.5 samples that were analyzed for elemental content using ion beam analysis techniques. Black carbon concentrations were determined using light reflection and PM₁₀ concentrations were recorded using colocated continuous PM monitors. PM₁₀ concentrations at both sites displayed a diurnal pattern, with hourly PM₁₀ concentration maxima in the evening (7 pm–midnight) and in the morning (7–9 am). One of the monitoring sites experienced consistently higher average PM₁₀ concentrations during every hour and analysis indicated that katabatic flows across the urban area contributed to the increased concentrations observed. Source apportionment using positive matrix factorization on the hourly data revealed four primary PM₁₀ sources for each site: biomass burning, motor vehicles, marine aerosol and crustal matter. Biomass burning was the most dominant source at both sites and was responsible for both the evening and morning PM₁₀ concentration peaks. The use of elemental speciation combined with PM₁₀ concentrations for source apportionment on an hourly time-scale has never been reported and provides unique and useful information on PM sources for air quality management.