Molecular characteristics and potential source of urban PM2.5-bound water-soluble organic matter in Shanghai during springtime

Abstract

Water-soluble organic matter (WSOM) is complicated component in atmospheric fine particulate matter (PM2.5) and has attracted increasing attentions due to their effects on air quality, climate change, and human health. In this study, the molecular characteristics and potential source of PM2.5-bound water-soluble organic matter in Shanghai during springtime were investigated using ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) coupled with electrospray ionization (ESI) source in negative ion mode. A total of 2537 monoisotopic molecular formulas were assigned in WSOM, and CHO, CHON, CHOS and CHNOS compounds were main components. Highly unsaturated CHO (DBE = 5.01−7.30) and CHON (DBE = 3.66−10.1) compounds were found in good weather days, while the highly oxygenated multifunctional CHOS compounds (O/C = 0.50−0.88) increased in slightly polluted days. Van Krevelen diagrams revealed that carbohydrates, lignin species, and protein species were the most abundant classes in all samples, which their relative abundance accounted for 81.8%. Comparison of our results with previously published data on atmospheric PM2.5 indicated that the biogenic aerosol and local industrial emission presented a larger impact on molecular compositions of WSOM in this region. These findings present a comprehensive overview of WSOM in Shanghai, which helps to understand their characteristics and sources.