TY - JOUR
T1 - Ozonolysis of fatty acid monolayers at the air–water interface: organic films may persist at the surface of atmospheric aerosols
AU - Woden, Benjamin
AU - Skoda, Maximilian W. A.
AU - Milsom, Adam
AU - Gubb, Curtis
AU - Maestro, Armando
AU - Tellam, James
AU - Pfrang, Christian
N1 - Funding Information:
Financial support. This research has been supported by the Natural
Publisher Copyright:
© 2021 American Society of Mechanical Engineers (ASME). All rights reserved.
PY - 2021/2/1
Y1 - 2021/2/1
N2 - Ozonolysis of fatty acid monolayers was studied to understand the fate of organic-coated aerosols under realistic atmospheric conditions. Specifically, we investigated the effects of temperature and salinity on the degradation of oleic acid at the air–water interface and the persistence of the aged surfactant film at the surface. The presence of a residual film is of atmospheric importance, as surface monolayers affect the physical properties of the droplets and because of the role they play in cloud formation. This occurs via several effects, most notably via surface tension reduction. The interplay between atmospheric aerosol loading and the formation, nature, and persistence of clouds is a key uncertainty in climate modelling.Our data show that a residual surface film, which we suspect to be formed of nonanoic acid and a mixture of azelaic and 9-oxononanoic acids, is retained at the interface after ozonolysis at near-zero temperatures but not at room temperature. Given the low-temperature conditions used here are atmospherically realistic, the persistence of a product film must be considered when assessing the impact of unsaturated fatty acid partitioned to the air–water interface. The presence of stable (non-oxidisable) reaction products also opens the possibility of build-up of inert monolayers during the aerosol life cycle with potential implications for cloud formation. Furthermore, we measured the kinetic behaviour of these films and found that the reactions are not significantly affected by the shift to a lower temperature with rate coefficients determined to be (2.2 ± 0.4) × 10−10 cm2 s−1 at 21 ± 1 ∘C and (2.2 ± 0.2) × 10−10 cm2 s−1 at 2 ± 1 ∘C.
AB - Ozonolysis of fatty acid monolayers was studied to understand the fate of organic-coated aerosols under realistic atmospheric conditions. Specifically, we investigated the effects of temperature and salinity on the degradation of oleic acid at the air–water interface and the persistence of the aged surfactant film at the surface. The presence of a residual film is of atmospheric importance, as surface monolayers affect the physical properties of the droplets and because of the role they play in cloud formation. This occurs via several effects, most notably via surface tension reduction. The interplay between atmospheric aerosol loading and the formation, nature, and persistence of clouds is a key uncertainty in climate modelling.Our data show that a residual surface film, which we suspect to be formed of nonanoic acid and a mixture of azelaic and 9-oxononanoic acids, is retained at the interface after ozonolysis at near-zero temperatures but not at room temperature. Given the low-temperature conditions used here are atmospherically realistic, the persistence of a product film must be considered when assessing the impact of unsaturated fatty acid partitioned to the air–water interface. The presence of stable (non-oxidisable) reaction products also opens the possibility of build-up of inert monolayers during the aerosol life cycle with potential implications for cloud formation. Furthermore, we measured the kinetic behaviour of these films and found that the reactions are not significantly affected by the shift to a lower temperature with rate coefficients determined to be (2.2 ± 0.4) × 10−10 cm2 s−1 at 21 ± 1 ∘C and (2.2 ± 0.2) × 10−10 cm2 s−1 at 2 ± 1 ∘C.
UR - http://www.scopus.com/inward/record.url?scp=85100303370&partnerID=8YFLogxK
U2 - 10.5194/acp-21-1325-2021
DO - 10.5194/acp-21-1325-2021
M3 - Article
SN - 1680-7316
VL - 21
SP - 1325
EP - 1340
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
IS - 2
ER -