Abstract. To quantify the total, direct and indirect impacts of fireworks individually, size-resolved PM samples were collected before, during and after a Chinese folk festival (Chinese New Year) in a megacity in China. Through chemical analysis and morphological characterisation, a strong influence of fireworks on the physicochemical characteristics of PM 10 and PM 2.5 was observed. The concentrations of many species exhibited an increasing trend during the heavy-firework period, especially for K + , Mg 2+ and Cr; the results of the non-sea-salt ions demonstrated an anthropogenic influence on K + and Mg 2+ . Then, source apportionment was conducted by receptor models and peak analysis (PA). The total influence of the fireworks was quantified by positive matrix factorisation (PMF), showing that the fireworks contributed higher fractions (23.40 % for PM 10 and 29.66 % for PM 2.5 ) during the heavy-firework period than during the light-firework period (4.28 % for PM 10 and 7.18 % for PM 2.5 ). The profiles of the total fireworks obtained by two independent methods (PMF and peak analysis) were consistent, with higher abundances of K + , Al, Si, Ca and organic carbon (OC). Finally, the individual contributions of the direct and indirect impacts of fireworks were quantified by chemical mass balance (CMB). The percentage contributions of resuspended dust, biomass combustion and direct fireworks were 36.8 ± 8.37 %, 14.1 ± 2.82 % and 44.4 ± 8.26 %, respectively, for PM 10 and 34.9 ± 4.19 %, 16.6 ± 3.05 % and 52.5 ± 9.69 %, respectively, for PM 2.5 , in terms of the total fireworks. The quantification of the total, direct and indirect impacts of fireworks in the ambient PM gives a original contribution for understanding the physicochemical characteristics and mechanisms of such high-intensity anthropogenic activities.