Contribution of nitrate and carbonaceous species to PM2.5 observed in Canadian cities

At a variety of Canadian monitoring sites, carbonaceous compounds were esti mated to account for an average of 50% of fine particle mass. These estimat es were determined by subtracting the total fine particle mass associated w ith inorganic compounds from the total fine mass determined gravimetrically . This approach, which yields an upper limit estimate of the total amount o f carbon-related mass was necessary since particulate carbon was not measur ed in the Canadian National Air Pollution Surveillance (NAPS) network. In t his paper, total carbon estimates are evaluated against organic and element al carbon measurements at locations in the Greater Vancouver area and Toron to. In addition, particle nitrate measurements at seven Canadian locations are used to determine the importance of nitrate relative to total mass and to examine the sampling artifacts due to the loss of particle nitrate from Teflon filters used in the NAPS dichotomous samplers.