¹H NMR Application for Characterizing Water-Soluble Organic Compounds in Urban Atmospheric Particles

Abstract

Water-soluble organic compounds (WSOC) in urban atmospheric particles separated by particle size were analyzed by 1H NMR. This is the first utilization of 1H NMR for characterizing WSOC in atmospheric particles. The WSOC dissolved in D2O were analyzed without a separation procedure. Twelve low molecular weight WSOC could be identified and their atmospheric concentrations determined. One of these, monomethyl hydrogen sulfate (MHS), was first detected in an urban area where no oil or coal power plant existed. Methanesulfonic acid (MSA) and hydroxymethanesulfonic acid (HMSA) were detected as major organosulfur compounds. Relatively high concentrations of these low molecular weight WSOC were observed in the particle diameter range of 0.43-1.1 microns. Many complex signals at 3-4 ppm in the NMR spectrum were seen only for the coarse particle samples (1.1 microns < particle diameter). Mannitol was believed to exist in the coarse particles as a major polyol corresponding to these signals. On the other hand, a large broad signal, observed at 2.5-3 ppm, was mostly present in the fine particles. Finally, it was believed that a major part of the WSOC in urban atmospheric fine particles is attributed to ketocarboxylic acids, ketodicarboxylic acids, and dicarboxylic acids.