Characteristics of carbonaceous aerosols in four northern Chinese cities during the 2022 Winter Olympics

To study the impact of control measures during the 2022 Winter Olympics on carbonaceous aerosols, samples of fine particulate matter (PM2.5) were collected in Zhangjiakou, Baoding, Shijiazhuang, and Handan in northern China from January to March 2022. The impacts of different intensities of control measures on organic carbon (OC) and elemental carbon (EC) in the four cities were analyzed. Compared with those in the precontrol period, the decreases in the PM2.5 concentrations in the four cities during the strict control period were ranked in the order of Zhangjiakou (53%), Handan (41%), Shijiazhuang (38%), and Baoding (36%); the decreases in the OC concentrations were ranked in the order of Zhangjiakou (40%), Shijiazhuang (22%), Baoding (21%), and Handan (16%); and the decreases in the EC concentrations were ranked in the order of Zhangjiakou (51%), Baoding (35%), Shijiazhuang (3%), and Handan (36%). The EC concentration in Handan increased rather than decreased throughout the strict control period. In Zhangjiakou, the reduction in secondary organic carbon (SOC) and primary organic carbon (POC) began notably before the strict control period, whereas in Baoding and Shijiazhuang, it began after the precontrol period. The efficiency of the control measures in lowering SOC was as follows: Baoding (38%), Zhangjiakou (32%), Handan (18%), and Shijiazhuang (12%). SOC formation was influenced by strict control measures that reduced pollution from coal combustion and vehicle exhaust in Zhangjiakou, Baoding, and Shijiazhuang. Conditional probability function (CPF) analysis and the potential source contribution factor (PSCF) were used to analyze the potential source regions of EC and OC during the four periods in each city. Transport from Inner Mongolia, Shanxi, the Beijing‒Tianjin‒Hebei region, and northern Henan primarily influenced the presence of EC and OC during the four periods in each city. This study provides theoretical suggestions for cities to optimize their emission control strategies.