Characteristics of fine particulate matter in Linyi during the 24th Olympic winter Games: An insight into the components, sources, transport pathways, and source distribution

To maintain air quality and mitigate pollution during the 24th Olympic Winter Games, strict control measures were implemented in Beijing and surrounding areas, including Linyi. Fine particulate matter (PM2.5) sampling was conducted in the urban area of Linyi between November 10th, 2021, and February 20th, 2022. This sampling period was divided into a no-control period (NCP) and a control period (CP). The PM2.5 concentration decreased by 25.0% during the CP, whereas the atmospheric oxidation increased. This led to the formation of secondary components of PM2.5. Although the conversion rate of the precursors into secondary components was increased during the CP, the nitrate (NO3 ) and ammonium (NH4+) concentrations were reduced due to emission reduction. Elemental carbon (EC) and primary organic carbon concentrations were also decreased, whereas the organic carbon (OC)/EC ratio and proportion of secondary organic carbon in PM2.5 increased. Total detected inorganic element concentrations decreased by 23.6% during the CP. The results of source apportionment revealed that secondary sources were the leading PM2.5 contributors during both periods. Vehicle pollution prevention and control should be strengthened as no restrictions on private-car travel during the CP. Controlling combustion and industrial sources had a significant impact on air quality during the CP. Biomass burning and industrial emissions declined from 20.7% to 16.1% (NCP) to 2.0% and 9.1% (CP), respectively. Backward trajectories revealed that air masses largely originated from local regions during both periods, with the highest PM2.5 concentrations found in air masses from the north (NCP) and east (CP) of Linyi. Potential source regions were also identified. The location of these regions showed that local and regional collaborative control of PM2.5 is urgently needed, particularly in northern and southern Linyi (NCP) and eastern Linyi (CP).