Measurement of organic and elemental carbon associated with PM2.5 during Pacific 2001 study using an integrated organic gas and particle sampler

In order to investigate the characteristics of carbonaceous components in fine particles in the Lower Fraser Valley of British Columbia, PM2.5 samples were collected twice a day for selected days in August 2001 for the measurement of particle-bound organic and elemental carbon (OC and EC). A denuder-based integrated organic gas and particle sampler (IOGAPS) was employed to minimize sampling artifacts often encountered during filter pack (FP) sampling. During IOGAPS sampling, the gas phase chemicals are removed by an XAD-coated denuder prior to the collection of particles by a quartz filter. The evaporation of the semivolatile organic carbon from the particle-laden filter is quantified by the backup XAD sorbent impregnated filters. A FP sampler was used for a comparison study. OC and EC were measured from filter punches by a thermal and optical transmittance aerosol carbon analyzer. There was no significant difference between the average IOGAPS-EC (0.50 μg C m−3) and FP-EC (0.32 μg C m−3), indicating that the particle loss during the transit in the denuder tube was negligible. The average OC determined by the IOGAPS was 2.80 μg C m−3, about 28% lower than that determined by the FP (3.59 μg C m−3), suggesting that the positive artifacts dominated during the FP sampling. The OC and EC concentrations in Vancouver were comparable with those at other background sites such as Kosan in Korea, but lower than those observed at typical urban sites such as Toronto and Seattle.