Source apportionment of PM_2.5 for 25 Chinese provincial capitals and municipalities using a source-oriented Community...

Source contributions to fine airborne particulate matter with aerodynamic diameters <2.5μm (PM_2.5) during 2013 were determined for 25 Chinese provincial capitals and municipalities using a source-oriented version of the Community Multiscale Air Quality (CMAQ) model. Based on the hierarchical clustering analysis of the observed PM_2.5 concentrations, the 25 cities were categorized into nine groups. Generally, annual PM_2.5 concentrations were highest in the cities in the north (81-154μgm^-3) and lowest in the cities close to seas in the south and east (27-57μgm^-3). Seasonal PM_2.5 observations in the cities were generally higher in winter than in the other seasons. Industrial or residential sources were predicted to be the largest contributor to PM_2.5 for all the city groups, with annually fractional contributions of 25.0%-38.6% and 9.6%-27%, respectively. The annual contributions from power plants, agriculture NH₃, windblown dust, and secondary organic aerosol (SOA) for the city groups were 8.7%-12.7%, 9.5%-12%, 6.1%-12.5%, and 5.4%-15.5%, respectively. Meanwhile, the annual contributions from transportation, sea salt, and open burning were relatively low (<8%, <2%, and <6%, respectively). Secondary PM_2.5 accounted for 47%-63% of total annual PM_2.5 concentrations in the cities and contributed to as much as 70% of daily PM_2.5 concentrations on PM_2.5 pollution days (daily concentrations>75μgm^-3). Industrial or residential sources were generally the largest contributor on PM_2.5 pollution days for all the city groups in each season, except that open burning, SOA, and windblown dust could be more important on some days, particularly in spring. The results of this study would be helpful to develop measures to reduce annual PM_2.5 concentrations and the number of PM_2.5 pollution days for different regions of China.