Daytime and nighttime PM2.5 samples were collected from an urban community in Tianjin. The major chemical components in PM2.5, including metal elements, polycyclic aromatic hydrocarbons and inorganic water-soluble ions, were monitored. A positive matrix factorization (PMF) model was used to apportion the potential sources of PM2.5 under different weather conditions. When the Air Quality Index (AQI) was below 200, the concentrations of BaA, BbF, BkF, Na and NO3- during the nighttime were higher than those during the daytime. PMF analysis indicated that secondary aerosols (37.3%), biomass burning (26.7%) and coal combustion (26.0%) were important sources of PM2.5 in the urban residential community when the AQI was greater than 200. When the AQI was less than 200 in the urban residential community, the main sources of PM2.5 in the urban residential community were secondary aerosols (50.7%) and fossil fuel combustion (47.2%). The pollution status of PM2.5 in the residential community of the urban area was serious, and the source apportionments of the PM2.5 samples in the urban area were different under different weather conditions.
Keywords: Air Quality Index; Daytime and nighttime; PM2.5; PMF; Source apportionment.