CaltechAUTHORS
Published February 14, 2023 | Version public
Journal Article Metadata-only

Molecular Understanding of the Enhancement in Organic Aerosol Mass at High Relative Humidity

Creators

Abstract

The mechanistic pathway by which high relative humidity (RH) affects gas–particle partitioning remains poorly understood, although many studies report increased secondary organic aerosol (SOA) yields at high RH. Here, we use real-time, molecular measurements of both the gas and particle phase to provide a mechanistic understanding of the effect of RH on the partitioning of biogenic oxidized organic molecules (from α-pinene and isoprene) at low temperatures (243 and 263 K) at the CLOUD chamber at CERN. We observe increases in SOA mass of 45 and 85% with increasing RH from 10–20 to 60–80% at 243 and 263 K, respectively, and attribute it to the increased partitioning of semi-volatile compounds. At 263 K, we measure an increase of a factor 2–4 in the concentration of C₁₀H₁₆O₂₋₃, while the particle-phase concentrations of low-volatility species, such as C₁₀H₁₆O₆₋₈, remain almost constant. This results in a substantial shift in the chemical composition and volatility distribution toward less oxygenated and more volatile species at higher RH (e.g., at 263 K, O/C ratio = 0.55 and 0.40, at RH = 10 and 80%, respectively). By modeling particle growth using an aerosol growth model, which accounts for kinetic limitations, we can explain the enhancement in the semi-volatile fraction through the complementary effect of decreased compound activity and increased bulk-phase diffusivity. Our results highlight the importance of particle water content as a diluting agent and a plasticizer for organic aerosol growth.

Additional Information

© 2023 The Authors. Published by American Chemical Society. We thank the European Organization for Nuclear Research (CERN) for supporting CLOUD with important technical and financial resources. This research has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 764991 ("CLOUD-MOTION H2020-MSCA-ITN-2017"), the Swiss National Science Foundation (no. 200021_169090, 200020_172602, 20FI20_172622, 206021_198140), the US National Science Foundation (NSF_AGS_1801280, NSF_AGS_1801574, NSF_AGS_1801897, and NSF_AGS_2132089), the German Federal Ministry of Education and Research (CLOUD-16 01LK1601A), and the Presidium of the Russian Academy of Sciences Program "Physics of Fundamental Interactions" 2017–2020. We thank the Jenny and Antti Wihuri Foundation for providing funding for this research and acknowledge Wiebke Scholz' doctoral scholarship from the University of Innsbruck (2021/2). This research was performed before the invasion of Ukraine by Russia on 24 February 2022. Author Contributions. M. Surdu, H.L, D.S.W., D.M.B, C.P.L., D.L., L.C., G.M., W.S., M.W., B.L., A.A.P., F.A., R.B., B.B., P.B., Z.B., L.D., J.D., H.F., X.-C.H., M. Simon, J.S., K.K., K.L., N.G.A.M., H.E.M., D.M., R. Marten, R. Mauldin, T.P., J.P., M.P., B.R., N.S.U., F.V., S.K.W., M.Z-W., A.W., and M.R. prepared the CLOUD facility or measuring instruments. M. Surdu, H.L., D.S.W., D.M.B., C.P.L., D.L., L.C., G.M., W.S., M.W., B.L., A.A.P., F.A., B.B., Z.B., J.D., H.F., X.-C.H., J.S., N.G.A.M., R. Marten, R. Mauldin, J.P., B.R., S.K.W., M.Z.-W., A.W., and M.R. collected the data. M. Surdu, H.L., D.S.W., D.M.B., D.L., L.C., G.M., W.S., M.W., B.L., A.A.P., F.A., M. Simon, R. Mauldin, S.K.W., A.W., M.R., and N.M.D. analyzed the data. M. Surdu, H.L., D.S.W., D.B., M.X., C.P.L., W.S., B.B., K.H., K.L., R. Mauldin, O.M., T.P., F.S., A.H., J.C., A.W., M.R., N.M.D., U.B., and I.E.H. contributed to the scientific discussion. M. Surdu, H.L., D.M.B., W.S., H.S., M.R., N.M.D., U.B., and I.E.H. participated in writing the manuscript. The authors declare no competing financial interest.

Additional details

Identifiers

PMCID
PMC9933880
Eprint ID
119880
Resolver ID
CaltechAUTHORS:20230307-207211000.49

Funding

CERN
Marie Curie Fellowship
764991
Swiss National Science Foundation (SNSF)
200021_169090
Swiss National Science Foundation (SNSF)
200020_172602
Swiss National Science Foundation (SNSF)
20FI20_172622
Swiss National Science Foundation (SNSF)
206021_198140
NSF
AGS-1801280
NSF
AGS-1801574
NSF
AGS-1801897
NSF
AGS-2132089
Bundesministerium für Bildung und Forschung (BMBF)
01LK1601A
Russian Academy of Sciences
Jenny and Antti Wihuri Foundation
University of Innsbruck

Dates

Created
2023-05-10
Created from EPrint's datestamp field
Updated
2023-05-10
Created from EPrint's last_modified field