关中城市一次重污染过程中大气碳质气溶胶变化特征及来源解析OA

To investigate the pollution characteristics and pollutant sources of carbonaceous aerosols during a heavy pollution episode in five cities of the Guanzhong cities,OC(organic carbon)and EC(elemental carbon)in the atmosphere of the five cities in the Guanzhong cities in November 2023 were taken as the research objects.The variations in mass concentrations of carbonaceous aerosols in each city of the Guanzhong cities were analyzed by means of the minimum OC/EC ratio method,potential source contribution factor(PSCF)analysis method and backward trajectory cluster analysis method.Whether OC and EC had the same source was inferred through the correlation and ratio between them.The organic carbon pollution characteristics of each city at different pollution stages were deduced based on the SOC/OC ratio.The relationship between polluting gases and the formation of carbonaceous aerosols was revealed by using the correlation between carbonaceous aerosols,polluting gases and meteorological factors.In addition,the traceability of pollutants was conducted by combining meteorological data.The results showed that the average mass concentrations of PM2.5,OC and EC in the Guanzhong region during the study period were(50.1±23.7),(9.2±3.5)and(1.7±0.8)μg/m3 respectively;Xianyang was affected by the most severe pollution,while Baoji suffered from the lightest pollution.Highly significant positive correlations were observed between OC and EC in all cities,indicating a high degree of homology.Based on the OC/EC ratios,all the five cities were found to be jointly affected by motor vehicle emissions,industrial emissions and coal combustion emissions,with obvious secondary transformation processes.According to the SOC/OC ratios,Xi'an and Xianyang were mainly impacted by primary organic carbon(POC),whereas Baoji,Tongchuan and Weinan were predominantly affected by secondary organic carbon(SOC)during the pollution period.Air masses from the southwest direction exerted the greatest influence on all cities during the pollution period,while air masses from the northwest direction dominated in the non-pollution period.Mutual transmission and influence of carbonaceous aerosols were confirmed among the five cities.The high-value centers of potential sources of carbonaceous aerosols were mainly distributed in the region itself,adjacent cities,western Gansu Province,northeastern Sichuan Province and southern Shaanxi Province.