Organic matter of the troposphere — V: Application of molecular marker analysis to biogenic emissions into the troposphere for source reconciliations

Organic matter in tropospheric aerosols is derived from two major sources and is admixed depending on the geographic area. These sources are biogenic detritus and anthropogenic emissions. The biogenic materials in the solvent-extractable organic matter are comprised predominantly of higher plant waxes, with lesser amounts of resin and microbial detritus and the anthropogenic components are primarily vehicular emissions (e.g. oils, soot, etc.) and input from combustion (e.g. charcoal, thermally-altered biogenic matter, etc.). Both biogenic detritus and anthropogenic emissions contain organic compounds (C₁₂–C₄₀₊), which can be identified with unique and distinguishable distribution patterns. Molecular composition analysis has been applied to such extracts after suitable chemical separation into subfractions (i.e. hydrocarbons, ketones, aldehydes, carboxylic acids, alcohols, and wax esters). Both homologous compound series and specific natural products (e.g. phytosterols, terpenes, etc.) are identified as molecular markers.Aerosols from rural and remote areas in the western United States, South America, Nigeria and Australia have been analyzed and all contained predominantly plant waxes. The loadings of hydrocarbons ranged approximately from 10–1400 ng/m³ of air, of fatty acids from 10–450 ng/m³ and of fatty alcohols from 10–1650 ng/m³. These higher molecular weight lipids primarily from flora comprise a major component of the organic carbon in rural and remote aerosols. They are thus important indicators for regional biogenic sources in the global cycling of organic carbon.Presented in part at the International Symposium on Biosphere-Atmosphere Exchange, Mainz, E.R. Germany, March 16–22, 1986, for Part IV see Simoneit et al. (1988) Atmos. Environ.22, 983–1004.