Distribution Characteristics and Source Analysis of Carbonaceous Aerosols Before and After the Spring Festival in the Guanzhong Plain

Abstract

The spatio-temporal variation characteristics and potential sources of carbonaceous aerosols in the Guanzhong Plain during the Spring Festival in 2023 were analyzed using inverse distance weighting spatial interpolation （IDW）, secondary organic carbon （SOC） estimation, and potential source contribution factor analysis （PSCF）, with the OC and EC in the PM2.5 of five cities： Xi'an, Baoji, Xianyang, Weinan, and Tongchuan as the research objects. The results showed that in terms of time distribution, ρ（OC） was as follows： after the Spring Festival [（18.6 ±11.0） μg·m-3] &gt; during the Spring Festival [（16.2 ±15.1） μg·m-3] &gt; before the Spring Festival [（10.0 ±8.3） μg·m-3], and ρ（EC） was as follows： after the Spring Festival [（2.2 ±1.2） μg·m-3] &gt; during the Spring Festival [（1.7 ±1.5） μg·m-3] &gt; before the Spring Festival [（1.4 ±1.1） μg·m-3], which indicated that OC and EC concentrations were the most severe after the Spring Festival. In terms of spatial distribution, ρ（OC） was as follows： Xianyang [（21.4 ±17.3） μg·m-3] &gt; Baoji [（15.8 ±12.8） μg·m-3] &gt; Xi'an [（13.6 ±11.3） μg·m-3] &gt; Weinan [（11.6 ±9.1） μg·m-3] &gt; Tongchuan [（10.0 ±8.3） μg·m-3], and ρ（EC） was as follows： Xianyang [（2.1 ±1.4） μg·m-3] &gt; Weinan [（1.8 ±1.4） μg·m-3] &gt; Xi'an [（1.8 ±1.2） μg·m-3] &gt; Tongchuan [（1.6 ±1.4） μg·m-3] &gt; Baoji [（1.2 ±0.9） μg·m-3]. Overall, Xianyang had the most severe PM2.5 and carbon aerosol pollution, whereas Tongchuan had the least pollution. IDW results showed that the high-value center of OC and EC concentration [ρ（OC） &gt; 27.3 μg·m-3, ρ（EC） &gt; 2.9 μg·m-3] was in the middle of the plain, the low-value center of OC and EC concentration [ρ（OC） <7.0 μg·m-3, ρ（EC） < 1.0 μg·m-3] was in the northern plain, and the distribution of OC was higher in the west and lower in the east, whereas the distribution of EC was higher in the east and lower in the west. The proportion of SOC in OC was as follows： after the Spring Festival （51.7%） &gt; during the Spring Festival （41.1%） &gt; before the Spring Festival （36.8%）. The SOC/OC values of each city and the contribution rate of SOC of each city to the Guanzhong Plain indicated that Tongchuan, Baoji, and Xianyang were greatly affected by the secondary conversion of organic carbon. The correlation of OC and EC before, during, and after the Spring Festival （r = 0.85, r = 0.98, and r = 0.94, respectively） indicated a high degree of homology between them. Carbonaceous aerosols had a certain correlation with humidity and wind speed before and during the Spring Festival but had a weak correlation with meteorological factors after the Spring Festival. Carbonaceous aerosols generally were strongly correlated with CO and NO2, and the correlation was strongest after the Spring Festival, whereas the correlation with SO2 was strongest during the Spring Festival. The potential source areas of carbonaceous aerosols in the five cities were mainly concentrated in the local and surrounding areas of southern Gansu, northern Shaanxi, and southern Shaanxi. They were also affected by long-distance transportation from the northwest before the Spring Festival.