Chemical Characteristics of PM2.5 during 2015 Spring Festival in Beijing, China

Air pollution especially of PM_(2.5) pollution is a serious problem in Beijing. In order to quantify the effect of a festival in which pollution was expected to be reduced, we collected and analyzed PM_(2.5) samples in urban Beijing during the 2015 Spring Festival (from February 9^(th) to March 6^(th) 2015). We divided the sampling period into three phases: non-haze, haze and firework days. The average concentration of PM_(2.5) was highest on firework days at 248.9 μg m^(-3), followed by haze days (199.9 μg m^(-3)) and non-haze days (90.8 μg m^(-3)). The air quality of non-haze days during the holiday was better than that during non-holiday periods. Secondary inorganic ions (SO_4^(2-), NO_3^- and NH_4^+) were enriched on the haze days, while those on firework days contained large amounts of Cl^- and K^+, but small amounts of NO_3^- and NH_4^+. Ratios of NO_3^-/SO_4^(2-), SO_4^(2-)/K^+ and Cl^-/K^+ effectively distinguished the characteristics of PM_(2.5) between firework events and haze days. Ion balance calculations indicated that the acidity of PM_(2.5) from firework days was higher than that from haze and non-haze days. A method using enrichment factors (EF) found that crustal elements (EF 10 on all three types of days) included Ca, Al, Fe, Na, Co, Ni, P, Ti, and V; firework elements (EF 10 on firework days, significantly higher than haze days) were made up of Ba, Cr, Cu, Mg, Pb, S, Si, and Zn; common anthropogenic pollution elements (EF 10 in all three types of days) were As, Cd, Cu, Pb, S, Sb, Zn. Differences in chemical characteristics indicated that holidays such as the Spring Festival can affect air pollution patterns in two ways: a decrease in the population and vehicles but an increase in activities such as firework displays.