WATER-SOLUBLE ORGANICS IN ATMOSPHERIC PARTICLES - A CRITICAL-REVIEW OF THE LITERATURE AND APPLICATION OF THERMODYNAMICS TO IDENTIFY CANDIDATE COMPOUNDS

Although organic compounds typically constitute a substantial fraction of the fine particulate matter (PM) in the atmosphere, their molecula r composition remains poorly characterized. This is largely because at mospheric particles contain a myriad of diverse organic compounds, not all of which extract in a single solvent or elute through a gas chrom atograph; therefore, a substantial portion typically remains unanalyze d. Most often the chemical analysis is pet-formed on a fraction that e xtracts in organic solvents such as benzene, ether or hexane; conseque ntly, information on the molecular composition of the water-soluble fr action is particularly sparse and incomplete. This paper investigates theoretically the characteristics of the water-soluble fraction by spl icing together various strands of information from the literature. We identify specific compounds that are likely to contribute to the water -soluble fraction by juxtaposing observations regarding the extraction characteristics and the molecular composition of atmospheric particul ate organics with compound-specific solubility and condensibility for a wide variety of organics. The results show that water-soluble organi cs, which constitute a substantial fraction of the total organic mass, include CZ to C7 multifunctional compounds (e.g., diacids, polyols, a mino acids). The importance of diacids is already recognized; our resu lts provide an impetus for new experiments to establish the atmospheri c concentrations and sources of polyols, amino acids and other oxygena ted multifunctional compounds.