Preprints
https://doi.org/10.5194/egusphere-2023-2684
https://doi.org/10.5194/egusphere-2023-2684
12 Dec 2023
 | 12 Dec 2023

Measurement report: Secondary organic aerosols at a forested mountain site in southeastern China

Zijun Zhang, Weiqi Xu, Yi Zhang, Wei Zhou, Xiangyu Xu, Aodong Du, Yinzhou Zhang, Hongqin Qiao, Ye Kuang, Xiaole Pan, Zifa Wang, Xueling Cheng, Lanzhong Liu, Qingyang Fu, Douglas R. Worsnop, Jie Li, and Yele Sun

Abstract. Aerosol particles play crucial roles in both climate dynamics and human health. However, there remains a significant gap in our understanding of aerosol composition and evolution, particularly regarding secondary organic aerosols (SOA), and their interaction with clouds in high-altitude background areas in China. Here we conducted real-time measurements of submicron aerosols (PM1) using aerosol mass spectrometers at a forested mountain site (1128 m a.s.l.) in southeastern China in November 2022. Our results revealed that organic aerosol (OA) constituted a substantial portion of PM1 (41.1 %), with the OA being primarily of secondary origin, as evidenced by a high oxygen-to-carbon (O/C) ratio (0.85–0.96). Positive matrix factorization resolved two distinct SOA factors: less oxidized oxygenated OA (LO-OOA) and more oxidized OOA (MO-OOA). Interestingly, MO-OOA was scavenged efficiently during cloud events, while cloud evaporation contributed significantly to LO-OOA. The ratio of OA/ΔCO increased with a decrease in the O/C ratio, suggesting that OA remaining in cloud droplets generally maintained a moderate oxidation state. Furthermore, our results indicated a higher contribution of organic nitrates to total nitrate during cloudy periods (27 %) compared to evaporative periods (3 %). Notably, a substantial contribution of nitrate in PM1 (20.9 %) was observed, particularly during high PM periods, implying that nitrate formed in polluted areas interacted with clouds and significantly impacted the regional background site. Overall, our study underscores the importance of understanding the dynamics of secondary organic aerosols and the impacts of cloud processing in regional mountainous areas in southeastern China.

Zijun Zhang, Weiqi Xu, Yi Zhang, Wei Zhou, Xiangyu Xu, Aodong Du, Yinzhou Zhang, Hongqin Qiao, Ye Kuang, Xiaole Pan, Zifa Wang, Xueling Cheng, Lanzhong Liu, Qingyang Fu, Douglas R. Worsnop, Jie Li, and Yele Sun

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2684', Anonymous Referee #1, 04 Feb 2024
  • RC2: 'Comment on egusphere-2023-2684', Anonymous Referee #2, 06 Feb 2024
  • RC3: 'Comment on egusphere-2023-2684', Anonymous Referee #3, 12 Feb 2024
Zijun Zhang, Weiqi Xu, Yi Zhang, Wei Zhou, Xiangyu Xu, Aodong Du, Yinzhou Zhang, Hongqin Qiao, Ye Kuang, Xiaole Pan, Zifa Wang, Xueling Cheng, Lanzhong Liu, Qingyang Fu, Douglas R. Worsnop, Jie Li, and Yele Sun

Data sets

Measurement report: Secondary organic aerosols at a forested mountain site in southeastern China [Data set] Z. Zhang et al. https://doi.org/10.5281/zenodo.10312334

Zijun Zhang, Weiqi Xu, Yi Zhang, Wei Zhou, Xiangyu Xu, Aodong Du, Yinzhou Zhang, Hongqin Qiao, Ye Kuang, Xiaole Pan, Zifa Wang, Xueling Cheng, Lanzhong Liu, Qingyang Fu, Douglas R. Worsnop, Jie Li, and Yele Sun

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Short summary
We investigated aerosol composition, sources, and the interaction between secondary organic aerosol (SOA) and clouds at a regional mountain site in southeastern China. Clouds efficiently scavenge more-oxidized SOA; however, cloud evaporation leads to the production of less-oxidized SOA. The unexpectedly high presence of nitrate in aerosol particles indicates that nitrate formed in polluted areas has undergone interactions with clouds, significantly influencing the regional background site.