Highly oxygenated molecules and their chemistry in polluted urban environments

Highly oxygenated molecules (HOMs) are important atmospheric oxidation products that may contribute to new particle formation and initial particle growth. Thousands of such compounds were quantified in both winter and summer of 2016 in Beijing by using online nitrate ion chemical ionization time-of-flight mass spectrometry. Positive-matrix factorization of the time series of the high-resolution mass spectra identified at least 10 major groups of gaseous HOMs in Beijing. We compared these PMF factors with the HOMs produced in a Potential Aerosol Mass (PAM) flow reactor in the laboratory from the oxidation of typical biogenic and aromatic precursors under various oxidation conditions. Our results show that four of the ten PMF factors perhaps correspond to biogenic precursors, and another four factors are likely related to aromatic precursors. The chemistry of these aromatic HOMs are discussed based on the results from the PAM experiments.