Evaluating the Effects of Springtime Dust Storms over Beijing and the Associated Characteristics of Sub-Micron Aerosol

In order to understand the characteristics, sources and processes of non-refractory submicron particles (NR-PM1), an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed to acquire observational data during the spring (April 1 to 30) in Beijing, China, in 2012. Based on PM10, PM2.5 and NR-PM1 mass concentrations observation, satellite images and the back trajectory analysis, one haze and dust storm episodes were recorded during the campaign, in addition, one clean episodes was also added to the comparison as a reference. The NR-PM1 mass concentration was 97 mu g m(-3) during the haze episodes, while it was approximately 12 times and 1.7 times that on the clean and dust episodes, respectively. In addition, the secondary inorganic aerosol (sulfate, nitrate and ammonium) contributed the largest fraction of NR-PM1 (69%) during the haze episodes. The dust storms originated from the northwestern caused the PM10 peaking at 826 mu g m(-3), with an average of 364 +/- 186 mu g m(-3) and higher than the haze episodes (241 mu g m(-3)). In addition, compared to the clean episodes (the NR-PM1 mass was 8 mu g m(-3)), the dust storms caused the average NR-PM1 mass reaching 56 mu g m(-3), corresponding to the secondary components significantly increased, including sulfate (9.5 mu g m(-3)), nitrate (8 mu g m(-3)), ammonium (6 mu g m(-3)) and OOA (6 mu g m(-3)). The backward trajectory clustering analysis indicated the air mass from the southeast (at a frequency more than 30%) contained the higher NR-PM1 concentration (more than 80 mu g m(-3)) corresponding to the higher sulfate, nitrate and ammonium contributions.