Abstract: We investigated by ICP-MS the trace elemental compositions of PM2.5 in Beijing after the implementation of the ‘action plan’ for comprehensive control of air pollution. The results showed that PM2.5 mainly contained 7 trace elements, Zn, Mn, Ba, Pb, Cr, Cu and Ti, with Zn ranked the highest in content. The water-soluble form of Zn, Cd, Tl, Cs or Rb accounted for more than 80% of its total content in PM2.5, revealing that most trace elements occur water-soluble in fine particles. Interestingly, trace elemental contents (10-6) in PM2.5 samples decreased with increasing PM2.5 pollution levels, whereas, mass concentrations (ng·m-3) increased with increasing pollution levels, the same trend as PM2.5 mass concentration. It indicated that the content of trace elements in PM2.5per unit mass is only related to the composition of particles, not the concentration of particles. The trace elements in PM2.5 during the sampling period were mainly from soil dust (48.27%), combustion sources and industrial emissions (16.16%) and vehicle brake and tire wear (10.03%), followed by automobile exhaust (5.84%), construction dust (4.88%) and other sources (3.68%). Compared with the results before the action for comprehensive air pollution control, the mass concentration of trace elements in PM2.5 after the action decreased significantly, with the greatest decrease of 80.3% at high pollution level.

Key words: Beijing City, the action for comprehensive control of air pollution, PM2.5, trace elements, ICP-MS