Atmospheric formaldehyde, acetaldehyde, and acetone in five major Chinese cities : photochemical characteristics, sources, and joint ozone-carbonyl control strategies

Abstract

Formaldehyde, acetaldehyde, and acetone are the most abundant carbonyl-containing volatile organic compounds (VOCs), with aldehydes posing health risks and acting as important photochemical intermediates that contribute to tropospheric ozone (O<inf>3</inf>) pollution. This study intercompared the characteristics of three carbonyls from simultaneous sampling in five major Chinese cities in the summer of 2018 and further assessed their sources, photochemical behavior, and environmental impacts using modeling approaches. Observations showed that Beijing (9.6 ± 0.1 ppbv) and Wuhan (5.2 ± 0.1 ppbv) exhibited the high formaldehyde concentrations, followed by Shanghai, Chengdu, and Lanzhou. Model simulation revealed the anthropogenic alkenes accounted for over 50 % formaldehyde in Beijing and Lanzhou, while isoprene influenced 10–20 % in other cities. Other VOC species contributed 1–2 % each, highlighting the complexity of VOC contributions for formaldehyde. In contrast, acetaldehyde and acetone were mainly produced from propene and α/β-pinene, respectively (about 50 % each), with the top ten VOCs accounting for around 90 %. Furthermore, carbonyls were quantified for O<inf>3</inf> formation across the cities, with the highest in Beijing (33 %) and the lowest in Lanzhou (6 %). The comparison of their isopleths suggestsed that O<inf>3</inf> reduction strategies can also effectively reduce carbonyls. Finally, source apportionment combined with chemical mechanisms traced sources of primary and secondary carbonyls, showing that vehicle emissions rich in alkenes were the largest contributors to the secondary aldehyde formation in all five cities. Including their primary contributions, vehicles accounted for 40–50 % of total aldehydes, followed by solvent usage. For acetone, biogenic sources dominated over anthropogenic ones. These findings deepen our understanding of carbonyl photochemistry and possible future mitigation strategies.