[Analysis of Pollution Characteristics and Primary, Secondary Contributions of Firework Burnings in Qingdao During the Spring Festival].

Atmospheric pollution frequently occurs in northern China during winter heating period, wherein nitrate became the dominant driver for PM _2.5 accumulations. However, sulfate accumulation was found to be significantly higher than that of nitrate during firework burning events and exhibited different pollution characteristics. Online data available from February 2, 2019 to February 10, 2019, including observation data measured from AIM-IC in suburban Qingdao and meteorological data from national automatic monitoring station, were analyzed. The results showed that particulate accumulation, dust and firework burning events were observed. The primary contribution rates of the most intensive firework burning to PM _2.5 and PM ₁₀ were 69.8% and 63.8%, respectively. In contrast to a severe accumulation of nitrate during the particulate accumulation event, the sulfate formed prior and exhibited more severe accumulation than nitrate during the firework burning events. The primary contribution factors n (SO ₄ ^2- )/ n (K ⁺ ) and n (NO ₃ ^- )/ n (K ⁺ ) of firework burnings was 1.2 and 1.3 (molar ratios), respectively. The secondary contribution factors were 2.1 and 1.6 times, under relatively stable meteorological conditions. However, during the transit of dry and cold air, the value of secondary contribution factors decreased substantially and exhibited nearly the same values as the primary ones.