Characteristics of polar organic compounds from diesel truck emissions measured by FT-ICR MS.

Water-soluble organic compounds (WSOC) and dichloromethane: methanol-soluble organic compounds (DMSOC) in polar organic compounds (POCs) present in emissions from a diesel truck were characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The main compositions and molecular structures of WSOC and DMSOC were investigated and classified into three groups based on their elemental compositions: CHO, CHON, and S-containing compounds (CHONS and CHOS) (namely WSOC CHO ; WSOC CHON ; WSOC OS ; DMSOC CHO ; DMSOC CHON and DMSOC OS). The main results are as follows. (1) The order of groups in WSOC and DMSOC in terms of peak response was CHO (WSOC: 52.2% and DMSOC: 64.5%), CHON (WSOC: 43.4% and DMSOC:25.9%), and S-containing compounds (WSOC: 4.35% and DMSOC: 9.57%). (2) The relative response of compounds with low H/C and O/C ratios and double-bond equivalents (DBE) > 10 in WSOC CHO was twice that of DMSOC CHO , indicating that the WSOC emitted by diesel trucks might contain many highly condensed benzene rings. Compounds with H/C = 2 and DBE = 1 in DMSOC CHO showed a strong relative response, presumably due to a fatty-acid structure, which might be used as a tracer to distinguish emissions from diesel trucks and other pollution sources. (3) The strongest relative response in WSOC CHON was for C 11 H 7 O 5 N 2 with an aromaticity equivalent (Xc) = 2.5 and DBE = 9, suggesting that dinitrophenol or methyl nitrophenol might be present. Moreover, C 39 H 76 O 8 N 1 with Xc = 0 and DBE = 2 was dominant in DMSOC CHON , suggesting the presence of carboxylic acids. (4) In both WSOC and DMSOC, long-chain aliphatic and organic sulfate compounds accounted for the largest proportion of S-containing compounds. However, the contents of condensed hydrocarbons and aromatic rings in DMSOC OS were higher than those in WSOC OS , which suggests that DMSOC OS has a strong optical absorption ability. Thus, this study effectively determined the POC compounds of diesel truck emissions and their possible structures, providing data for assessing the environmental effects of using diesel trucks. [Display omitted] • Molecular structures emitted from truck were differences between WSOC and DMSOC. • Condensed benzene and fatty acid were dominated in WSOC CHO and DMSOC CHO. • Dinitrophenol or methyl nitrophenol assumed as tracers for trucks emissions. [ABSTRACT FROM AUTHOR]