Effect of fireworks events on urban background PM2.5 composition:  measurement of trace elements at SORPES during spring festival periods 2016-2018

  Burning firework is a traditional custom in China during Chinese Spring festival period, and the smoke plums releasing from firework burning are responsible for high concentrations of particles (especially trace metals) and gases. In this work，results from in-situ measurements of chemical components of PM2.5 aerosols and trace gases during three successive spring festival campaigns (2016-2018) are reported. The campaigns were carried out at a regional background station, SORPES, located in the western part of the Yangtze River Delta in eastern China.  Table 1. Median value of selected trace metals, PM2.5 mass, organic carbon, elemental carbon, ions and trace gas concentration during firework events (FW) and background (BG) periods in three campaigns.    2016 2017 2018   FW BG FW BG FW BG ug/m3             PM2.5 63 54 40 63 59 43 OC 12 7.7 6.5 7.8 4.7 4.4 EC 3.4 2.7 1.8 2.8 2.4 2.7 K 3.1 0.8 1.0 0.5 1.2 0.2 Cl 1.2 1.6 1.0 1.0 1.5 0.8 SO4 11 12 9.2 12 12 7.3 ng/m3             Sr 60 8.2 16 5.5 35 7.4 Ba 137 14 33 11 87 17 Cu 26 10 9.4 6.1 50 37 As 36 23 11 15 13 11 Pb 139 83 60 75 60 46 Zn 90 109 70 127 73 84 Fe 338 369 150 265 174 318 V 2.3 0.8 1.9 2.2 0.7 0.6 CO(ppm) 0.83 0.53 0.48 0.64 0.56 0.55 SO2(ppb)     2.0 3.6 1.4 2.5 Sr/PM(‰) 1.03 0.2 1.01 0.11 0.98 0.2   Median concentrations of selected PM2.5 chemical species and trace metals are summarized in Table1. Clear elevations of Sr, Ba, Cu, K and Cl were observed during firework event period than background period, while no clear elevation were found for other species. Time series illustrated in Fig.1 suggested that in our case, Sr followed by Ba were recognised as the best fireworks tracers because their concentration were very high during firework episode and comparable with the detection limits of instrument during the background period. Similar founding was also observed in Spain (Moreno et al., 2010). The higher Sr/PM2.5 ratio (Table 1) suggest higher contribution of firework emission pollution to PM2.5 during firework events compare to background period (5 to 10 times). Figure 1. Time series of Sr and Ba during three campaigns in 2016-2018.   Extremely high enrichment factor was determined for Sr, Ba, Cu, Zn and Pb, suggests that they have anthropogenic origin. Mass concentrations of the trace elements and OC, EC data were input into EPA PMF5.0 model to elucidate the possible dominant source. The results suggest that the dominant sources in three campaigns were firework, coal burning, industry, and traffic. Further analysis on PMF and back trajectory statistics are still need to be done.