Characterization of water-soluble organic compounds in atmospheric aerosol: A new approach

A new methodological approach is proposed to characterize aerosol water-sol uble organic compounds (WSOC). Real aerosol and fog water samples were subj ected to a procedure based on a combination of chromatographic separations, functional group investigation by proton nuclear magnetic resonance (HNMR) , and total organic carbon determination. The complex mixture of aerosol/fo g WSOC was separated by a chromatographic procedure into three main classes of compounds: (1) neutral/basic compounds; (2) mono- and di-carboxylic aci ds; (3) polyacidic compounds. Characterization by HNMR spectroscopy showed that fraction 1 is mainly composed of polyols or polyethers, fraction 2 is mainly composed of hydroxylated aliphatic acidic compounds, while fraction 3 is composed of highly unsaturated polyacidic compounds of predominantly a liphatic character, with a minor content of hydroxyl- groups. Quantitative data on the three classes of compounds were then derived from total organic carbon analysis, showing that the three separated fractions together accou nt for 77% (in terms of C) of the total WSOC concentration of a fog water s ample. Further quantitative information on the functional groups present in the three separated fractions can be obtained from HNMR spectra. This newl y proposed approach to aerosol WSOC characterization provides comprehensive and synthetic information on aerosol organic composition which can be help ful for modeling purposes and is also particularly useful when aerosol chem ical mass closure is pursued.