Fossil- and bio-mass combustion: C-14 for source identification, chemical tracer development, and model validation

Carbonaceous gases and aerosols emitted during fossil- and bio-mass combustion processes have significant impacts on regional health and visibility, and on global climate. ¹⁴C accelerator mass spectrometry (AMS) has become the accepted standard for quantitatively partitioning individual combustion products between fossil and biospheric sources. Increased demands for source apportionment of toxic gases/vapors such as carbon monoxide and benzene, and toxic aerosol species such as polycyclic aromatic hydrocarbons, however, have led to increased needs for chemical source tracers. As a result, the application of atmospheric ¹⁴C measurements has been extended to the discovery of new chemical tracers and the validation of the related apportionment models. These newer applications of ¹⁴C are illustrated by recent investigations of: 1) sources of excessive concentrations of carbon monoxide and benzene in the urban atmosphere during the winter, as related to combustion source control strategies; and 2) the development/validation of potassium and hydrocarbon tracer models for the apportionment of mutagenic aerosols from biomass (wood) burning and motor vehicle emissions. Among the important consequences of these studies are new insights into potential limitations of elemental tracer models for biomass burning, and the impact of bivariate (isotopic, mass) chemical blanks on atmospheric ¹⁴C-AMS data.