AVS 64th International Symposium & Exhibition
    Applied Surface Science Division Wednesday Sessions
       Session AS+BI+MI+NS+SA+SS-WeM

Paper AS+BI+MI+NS+SA+SS-WeM1
Photolysis of Pyruvic Acid in Aqueous Solution as a Source of Aqueous Secondary Organic Aerosol

Wednesday, November 1, 2017, 8:00 am, Room 13

Session: Beyond Traditional Surface Analysis: Pushing the Limits
Presenter: Yao Fu, Pacific Northwest National Laboratory
Authors: Y. Fu, Pacific Northwest National Laboratory
X.F. Yu, Pacific Northwest National Laboratory
F. Zhang, Pacific Northwest National Laboratory
Z.H. Zhu, Pacific Northwest National Laboratory
J.M. Chen, Fudan University
X.Y. Yu, Pacific Northwest National Laboratory
Correspondent: Click to Email
Pyruvic acid are found in fogs, aerosols and clouds. The sunlight driven reaction pathways of pyruvic acid in the aqueous phase are more elusive compared to its well-known gas phase chemistry. Aqueous solutions containing pyruvic acid in a microchannel after different UV photolysis times up to 8 hours have been studied by in situ liquid time-of-flight secondary ion mass spectrometry (ToF-SIMS) for the first time. Both positive and negative ion mode mass spectra provided complementary information of the photochemical aging products at the solution surface. Compared with previous results using bulk approaches (i.e., NMR, ESI-MS), our unique liquid surface molecular imaging enables the observation of photochemical products of pyruvic acid at the aqueous solution surface including oxidation products (i.e., acetic acid, oxalic acid, formic acid, lactic acid), oligomers (i.e., dimethyltartaric acid), and water clusters (i.e., (H2O)nH+, (H2O)nOH-) with submicrometer spatial resolution. Spectral principal component analysis is used to determine similarities and differences among various photochemical aging samples. SIMS three-dimensional chemical mapping permits visualization of the surface mixing state at the molecular level. For example, oligomers and oxidation products become more significant shown in the chemical spatial mapping with increased photolysis time. In situ molecular imaging of the pyruvic acid aqueous solution surface provides new understanding of complex photochemical reactions as an important source of aqueous secondary organic aerosol (SOA) formation in atmospheric chemistry.