GEOCHEMICAL INVESTIGATIONS OF ORGANIC MATTER CONTAINED IN AMBIENT AEROSOLS AND RAINWATER PARTICULATES (ACID, HYDROCARBONS, DEPOSITION, AIR POLLUTION, AROMATIC).

摘要

Geochemical techniques have been applied to organic matter in ambient aerosols and rainwater particulates. Two comparative studies were conducted with sample acquisitions from West Los Angeles, California, during 1982. Determinations of (1) ambient concentrations for the acid, neutral, and acid + neutral lipid species, (2) mass loadings of the unresolved-to-resolved components, and (3) major homolog series, were carried out for all sample extracts. Close examination of these bulk parameters provides useful chemical distinctions which permit discussion of the sources, fates, and spatial distributions of the atmospheric lipid fraction.; Source materials are primarily anthropogenic in origin for the fine and total atmospheric aerosols and for the rainwater particles. Petroleum and combustion residues are the dominant lipid components. Biological materials consisting of bacterial lipids and plant waxes are present, generally in subordinate amounts. Rain particulate extracts are an exception, where bacterial fatty acids can comprise up to 65% of the total mass of extractable organic carbon.; Seasonal variations are evident for the fine and total atmospheric aerosols. Winter maxima and summer minima concentrations have been determined for both the neutral and acid + neutral fractions. These data suggest that photochemical processes do not generate the major fraction of airborne particulate organic carbon.; Total ambient aerosols collected before, during, and after discrete storm events, show slight reductions in atmospheric lipid concentrations for the later storm periods. This observation suggests that wet-depositional processes produce minor effects on the overall ambient levels of extractable organic carbon. Proportions of acid-to-neutral species isolated from rainwater particulates, show marked decreases for the final storm episodes, and correspond to reductions of the bacterial fatty acid components. Washout of airborne bacteria is suggested by these data. Conversely, the acidic fractions for the simultaneous total ambient aerosol samples, exhibit increased levels during rainfall conditions, and indicate the accumulation of organic acids which are associated primarily with the fine particle mode.