Abstract
Pyruvic acid (PA) is a ubiquitous 2-oxocarboxylic acid in the atmosphere. Its photochemical process at the air-liquid (a-l) interface has been suggested as an important source of aqueous secondary organic aerosols. We investigated the photochemical reaction pathways of PA at the a-l interface using synchrotron-based vacuum ultraviolet single-photon ionization mass spectrometry (VUV SPI-MS) coupled with the System for Analysis at the Liquid Vacuum Interface (SALVI) microreactor. Results from mass spectral analysis and the determination of appearance energies (AEs) indicate that photolysis of PA can generate radicals, then they recombine with carboxylic acids and simple molecular oligomers. Furthermore, the preliminary products could form larger oligomers via radical reaction or esterification in the presence of hydroxyl and carboxyl functional groups. Mass spectral comparison shows that most photochemical reactions would complete within 4 h. The expanded photochemistry-driven reaction flowchart of PA is proposed based on the newly discovered products. Our results reveal that the interfacial PA photochemical reactions have different mechanisms from the bulk liquid due to the interfacial properties, such as molecular density, composition, and ion concentration. Our findings show that in situ mass spectral analysis with bright photon ionization is useful to elucidate the contribution of a-l interfacial reactions leading to aqSOA formation.
| Original language | English |
|---|---|
| Article number | 172729 |
| Journal | Science of the Total Environment |
| Volume | 930 |
| DOIs | |
| State | Published - Jun 20 2024 |
Funding
Funding for XS was provided by Natural Science Foundation of Shandong Province, grant number ZR2022QB137. Funding for XYY was supported by the strategic Laboratory Directed Research and Development (LDRD) of the Physical Sciences Directorate of the Oak Ridge National Laboratory (ORNL). ORNL is managed by UT-Battelle, LLC, for the U. S. Department of Energy (DOE) under contract number DE-AC05-00OR22725. This research used resources of the Advanced Light Source (ALS), a Department of Energy (DOE) Office of Science User Facility under con-tract no. DE-AC02-05CH11231. Programmatic support for BX and OK was from the Office of Basic Energy Sciences of the U.S. DOE under Contract No. DE-AC02-05CH11231 at the Lawrence Berkley National Laboratory (LBNL), through the Gas Phase Chemical Physics Program and Condensed Phase, Interfaces, and Molecular Sciences Program. The authors thank Miss Rachel Komorek, Dr. Jiachao Yu, and Dr. Tyler Troy for their assistance in device fabrication, sample preparation, and data analysis. The authors also thank Dr. Musa Ahmed of LBNL for support of this research and access to the ALS beamline. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). Funding for XS was provided by Natural Science Foundation of Shandong Province , grant number ZR2022QB137 . Funding for XYY was supported by the strategic Laboratory Directed Research and Development (LDRD) of the Physical Sciences Directorate of the Oak Ridge National Laboratory (ORNL). ORNL is managed by UT-Battelle, LLC, for the U. S. Department of Energy (DOE) under contract number DE-AC05-00OR22725. This research used resources of the Advanced Light Source (ALS), a Department of Energy (DOE) Office of Science User Facility under con-tract no. DE-AC02-05CH11231. Programmatic support for BX and OK was from the Office of Basic Energy Sciences of the U.S. DOE under Contract No. DE-AC02-05CH11231 at the Lawrence Berkley National Laboratory (LBNL), through the Gas Phase Chemical Physics Program and Condensed Phase, Interfaces, and Molecular Sciences Program. The authors thank Miss Rachel Komorek, Dr. Jiachao Yu, and Dr. Tyler Troy for their assistance in device fabrication, sample preparation, and data analysis. The authors also thank Dr. Musa Ahmed of LBNL for support of this research and access to the ALS beamline.
Keywords
- Air-liquid interface
- Aqueous secondary organic aerosol (aqSOA)
- Photochemical aging
- Pyruvic acid
- SALVI
- VUV SPI-MS