Comprehensive observations of carbonyls in the Northern slope of the Tianshan Mountains: Characteristics, reactivity and sources
摘要
Ambient carbonyls were critical precursors of ozone (O3) and secondary organic aerosols. This study carried out an observation experiment including 30 species of carbonyls, other pollutants, and meteorological parameters at an urban site of Changji city in the Northern Slope of the Tianshan Mountains, China, from August 18 to September 6, 2021. The results showed that the total concentration of 30 carbonyls (Σ30carbonyls) was 20.76 µg/m3. The top three contributors were acetone (12.53 µg/m3), formaldehyde (4.06 µg/m3), and acetaldehyde (0.64 µg/m3), accounting for 82.98% of Σ30carbonyls. Comparisons with other studies indicated that the overall pollution level in Changji was comparable to northern industrial cities, while the relatively high concentrations of acetone and glyoxal deserve attention. The O3 production sensitivities were in the VOCs-limited regime during the daytime and gradually shifted from the VOCs-limited to the transitional regime from morning to afternoon. Based on the OH radical reactivity and the ozone formation potential analysis, the top five carbonyls contributing to O3 formation accounted for 75.14% and 86.83% of the total contributions, respectively. Among these, formaldehyde, acetaldehyde, and glyoxal were main active species affecting O3 formation. Machine learning analysis revealed that formaldehyde was primarily influenced by primary emissions, acetone and glyoxal were primarily influenced by secondary formation, while methylglyoxal was primarily influenced by atmospheric transport. The ratio analysis indicated that the formation of carbonyls in Changji resulted from multiple factors dominated by anthropogenic sources. Overall, this study provides evidence and clues for mitigating carbonyls and O3 pollution in the urban area of the northern slope of the Tianshan Mountains.