(2016) reported that water-soluble ions contributed 60% of the PM 2.5 mass during the summer months in Beijing and found that PM 2.5 samples were significantly acidic during hazy days. It has been shown that NH 4 +, NO 3 − and SO 4 2 − represent the major ions of PM 2.5 in the Beijing atmosphere accounting for 9.8%, 12.0% and 16% of the PM 2.5 mass (R.J. Water-soluble ions are important components of PM 2.5 (Yao et al., 2002, Chan and Yao, 2008, Gao et al., 2015). Hence, detailed investigations of the chemical and physical characteristics of PM 2.5 advance our understanding of their sources and formation mechanisms (Yao et al., 2002, Guo et al., 2010, Huang et al., 2014, Huang et al., 2014). However, the sources and formation processes of PM 2.5 in the atmosphere are not well constrained and differ from region to region. Of particular concern is particulate matter with an aerodynamic diameter ≤2.5 μm (PM 2.5) having a significant impact on human health, global climate change and regional visibility (Pope and Dockery, 2006, IPCC, 2007, Huang et al., 2014). In the past few years, Beijing is frequently suffering from haze events as do numerous cities in China (Chan and Yao, 2008 R.J. The sulfur and oxygen isotopes of the sulfate point to coal combustion as the major source of sulfate in PM 2.5 from the Beijing area. Notably, the air mass during the pollution control period originated mainly from north and northeast and changed to southerly directions thereafter. It is inferred that the decrease in concentration of sulfate in PM 2.5 mainly results from variations in air mass transport. 17.2 ± 6.0) in PM 2.5 during the air pollution control period and the non-source control period exhibit no significant differences, which suggests that despite a reduction in concentration, the sulfate source remains identical for the two periods. In contrast, the mean values of δ 34S sulfate (4.7 ± 0.8‰ vs. The results exhibit a decrease in concentration of water-soluble ions in PM 2.5 including aerosol sulfate. The water-soluble ions as well as sulfur and oxygen isotopes of sulfate in PM 2.5 collected between August 19 and Septem(n = 31) were analyzed in order to trace the sources and formation processes of PM 2.5 in Beijing. This distinct event provides an excellent opportunity for investigating the impact of such measures on the chemical properties of particulate matter with an aerodynamic diameter ≤2.5 μm (PM 2.5 ).

Strict pollution control measures have been carried out in Beijing prior to and during the 2015 China Victory Day Parade in order to improve air quality. Air pollution by particulate matter is a serious problem in Beijing.

2015 victory day parade