H-1 NMR application for characterizing water-soluble organic compounds in urban atmospheric particles

Water-soluble organic compounds (WSOC) in urban atmospheric particles separ ated by particle size were analyzed by H-1 NMR. This is the first utilizati on of H-1 NMR for characterizing WSOC in atmospheric particles. The WSOC di ssolved in D2O were analyzed without a separation procedure. Twelve low mol ecular weight WSOC could be identified and their atmospheric concentrations determined. One of these, monomethyl hydrogen sulfate (MHS), was first det ected in an urban area where no oil or coal power plant existed. Methanesul fonic acid (MSA) and hydroxymethanesulfonic acid (HMSA) were detected as ma jor organosulfur compounds. Relatively high concentrations of these low mol ecular weight WSOC were observed in the particle diameter range of 0.43-1.1 mum. Many complex signals at 3-4 ppm in the NMR spectrum were seen only fo r the coarse particle samples (1.1 mum < particle diameter). Mannitol was b elieved 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 tha t a major part of the WSOC in urban atmospheric fine particles is attribute d to ketocarboxylic acids, ketodicarboxylic acids, and dicarboxylic acids.