Characterization, sources and reactivity of carbonyl volatile organic compounds in North China: Based on long-term observations.

Carbonyl compounds play a pivotal role in the formation of secondary pollutants such as O3 and SOA, significantly impacting air quality and human health. This study extended the observation period compared to previous research, providing a long-term perspective on carbonyl compound variations and their environmental implications. Atmospheric observations were conducted at Beijing (BJ) and Xianghe (XH) during the summer and winter months of 2018, 2019, and 2023 to study the sources and impacts of carbonyl compounds in typical urban areas and peri‑urban areas. Notably, concentrations in the summer of 2023 increased compared to 2018 and 2019. The predominant carbonyl compounds-formaldehyde, acetaldehyde, and acetone-accounted for over 60 % of the total. The mean values of OFP in BJ ranged from 18.55 to 58.61 µg/m3, lower than those in XH (29.82 to 65.48 µg/m3), with formaldehyde and acetaldehyde contributing over 80 % of the total. SOAP exhibited a similar pattern, with values in XH (69.21 to 508.55 µg/m3) significantly exceeding those in BJ (34.47 to 159.78 µg/m3). The PMF model highlighted vehicle exhaust, secondary pollution, and biomass combustion as major sources of carbonyl compounds, emphasizing differences in source contributions between the two regions. This study's comparative analysis over different years and locations provides new insights into the dynamic changes in carbonyl compounds and their environmental importance. These results not only reinforce the importance of carbonyl compounds regulation but also offer a valuable reference for evaluating and refining emission control strategies during this period.