posted on 2024-01-08, 05:45authored byDandan Li, Wei Huang, Dongyu Wang, Mingyi Wang, Joel A. Thornton, Lucía Caudillo, Birte Rörup, Ruby Marten, Wiebke Scholz, Henning Finkenzeller, Guillaume Marie, Urs Baltensperger, David M. Bell, Zoé Brasseur, Joachim Curtius, Lubna Dada, Jonathan Duplissy, Xianda Gong, Armin Hansel, Xu-Cheng He, Victoria Hofbauer, Heikki Junninen, Jordan E. Krechmer, Andreas Kürten, Houssni Lamkaddam, Katrianne Lehtipalo, Brandon Lopez, Yingge Ma, Naser G. A. Mahfouz, Hanna E. Manninen, Bernhard Mentler, Sebastien Perrier, Tuukka Petäjä, Joschka Pfeifer, Maxim Philippov, Meredith Schervish, Siegfried Schobesberger, Jiali Shen, Mihnea Surdu, Sophie Tomaz, Rainer Volkamer, Xinke Wang, Stefan K. Weber, André Welti, Douglas R. Worsnop, Yusheng Wu, Chao Yan, Marcel Zauner-Wieczorek, Markku Kulmala, Jasper Kirkby, Neil M. Donahue, Christian George, Imad El-Haddad, Federico Bianchi, Matthieu Riva
Highly
oxygenated organic molecules (HOMs) are a major
source of
new particles that affect the Earth’s climate. HOM production
from the oxidation of volatile organic compounds (VOCs) occurs during
both the day and night and can lead to new particle formation (NPF).
However, NPF involving organic vapors has been reported much more
often during the daytime than during nighttime. Here, we show that
the nitrate radicals (NO3), which arise predominantly at
night, inhibit NPF during the oxidation of monoterpenes based on three
lines of observational evidence: NPF experiments in the CLOUD (Cosmics
Leaving OUtdoor Droplets) chamber at CERN (European Organization for
Nuclear Research), radical chemistry experiments using an oxidation
flow reactor, and field observations in a wetland that occasionally
exhibits nocturnal NPF. Nitrooxy-peroxy radicals formed from NO3 chemistry suppress the production of ultralow-volatility
organic compounds (ULVOCs) responsible for biogenic NPF, which are
covalently bound peroxy radical (RO2) dimer association
products. The ULVOC yield of α-pinene in the presence of NO3 is one-fifth of that resulting from ozone chemistry alone.
Even trace amounts of NO3 radicals, at sub-parts per trillion
level, suppress the NPF rate by a factor of 4. Ambient observations
further confirm that when NO3 chemistry is involved, monoterpene
NPF is completely turned off. Our results explain the frequent absence
of nocturnal biogenic NPF in monoterpene (α-pinene)-rich environments.