Impact of emissions controls on ambient carbonyls during the Asia-Pacific Economic Cooperation summit in Beijing, China

Beijing and its surrounding areas implemented a series of stringent measures to ensure good air quality during the Asia-Pacific Economic Cooperation (APEC) summit. These measures included restrictions on traffic, constructions, and industrial activities. The diurnal variations of carbonyls, 24-h PM2.5, and its chemical species were investigated before, during, after APEC, and the 2015 summer. The average concentrations of carbonyls, formaldehyde, acetaldehyde, and acetone were decreased by 65.2%, 78.6%, 41.5%, and 55.6% during APEC, respectively. The concentrations of propene equivalent, the ozone formation potential, and the contribution to OH· removal by carbonyls during APEC were approximately 27–33% of those during the preceding interval. The temporal variation of carbonyls during APEC was similar to that of other air pollutants, except for O3; however, the diurnal variation of carbonyls was consistent with that of O3, with the highest values at noon and the lowest ones at night during APEC. Large variations in C1/C2 (0.95–9.41) and C2/C3 (5.70–15.71) were observed during the sampling period. The correlations analysis, diagnostical ratios, and diurnal variations of carbonyls indicated that primary sources were not an important source and secondary formation was the dominant source of atmospheric carbonyls during the entire period. The control measures not only reduced primary carbonyl emissions but also dramatically reduced secondary carbonyl precursors, such as NOx and volatile organic compounds (VOCs), resulting in the low level of carbonyls during APEC. In addition, the potential health effects of carbonyls were evaluated and the cancer risk from formaldehyde and acetaldehyde was significantly higher before APEC than during the other intervals.