Characterization of lead-containing atmospheric particles in a typical basin city of China: Seasonal variations, potential source areas, and responses to fireworks.

Lead (Pb) in individual aerosol particles was measured using a single particle aerosol mass spectrometer at an urban site in Chengdu, a typical basin city of China, for four one-month periods in 2016–2017 – one period for each season. The highest mass concentrations of particulate matter (PM) and gaseous species (CO, NO, NO2, and SO2) were observed in winter. Cluster analysis was applied to Pb-containing particles, and eight major classes were identified based on mass spectral features. The contribution of these classes to the total Pb-containing particles varied seasonally – for example, Pb-nitrate (PbNO3) particles showed a higher contribution in spring and winter (47%), while Pb-sulfate (PbSO4) particles exhibited a higher contribution in summer and autumn (14%–19%). The size range of particles also changed with seasons as a result of different sources and formation mechanisms under different climatic conditions. A weighted potential source contribution function (WPSCF) analysis suggested that the potential source areas of Pb-containing particles were mainly located to the northeast, east, southeast, and south of Chengdu, and their contribution intensity and coverage area significantly varied in the four seasons. Although almost all pollutants decreased during the Spring Festival holiday (SF) period, fireworks caused the most serious PM and SO2 pollution episodes during the whole study period. During the SF period, the contributions of industrial and traffic-related particles (Pb-organic + elemental carbon (PbOE) and PbNO3 particles) decreased, whereas those of Pb-chloride (PbCl), Pb-metal (PbM), and Pb-sulfate + nitrate (PbSN) particles increased due to fireworks. Results from this study may provide valuable information for a deeper understanding of Pb in particles and evaluation its impacts on atmospheric environment and human health.