期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：32
DOI：10.1073/pnas.2201729119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Unique in the marine boundary layer, new particle formation involves iodine-oxide nucleation; however, challenges remain in explaining the growth. Condensation of organic vapors has been suggested as the most probable mechanism, but condensation growth requires condensing organic molecules of low effective volatilities. Here, we show, through a combination of laboratory experiments, ambient field measurements, and model studies, that exposure of iodine-oxide nanoparticles to organic vapors may lead to accelerated particle growth through heterogeneous reactions forming low-volatility organic acids and alkylaminium salts in the particle phase. Moreover, we show that a notable fraction of iodine is recycled back into the gas phase during particle growth, providing insights into iodine-organic multiphase reactions for marine new particle formation.
The gas-phase formation of new particles less than 1 nm in size and their subsequent growth significantly alters the availability of cloud condensation nuclei (CCN, >30–50 nm), leading to impacts on cloud reflectance and the global radiative budget. However, this growth cannot be accounted for by condensation of typical species driving the initial nucleation. Here, we present evidence that nucleated iodine oxide clusters provide unique sites for the accelerated growth of organic vapors to overcome the coagulation sink. Heterogeneous reactions form low-volatility organic acids and alkylaminium salts in the particle phase, while further oligomerization of small α-dicarbonyls (e.g., glyoxal) drives the particle growth. This identified heterogeneous mechanism explains the occurrence of particle production events at organic vapor concentrations almost an order of magnitude lower than those required for growth via condensation alone. A notable fraction of iodine associated with these growing particles is recycled back into the gas phase, suggesting an effective transport mechanism for iodine to remote regions, acting as a “catalyst” for nucleation and subsequent new particle production in marine air.
关键词：enmarine new particle formationheterogeneous reactioniodineintermediate oxidized organics
