Univariate and multivariate exploration of urban carbonaceous aerosol data have revealed some interesting and important facets of aerosol carbon characteristics, sources and modeling assumptions. Data were obtained fr...
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Univariate and multivariate exploration of urban carbonaceous aerosol data have revealed some interesting and important facets of aerosol carbon characteristics, sources and modeling assumptions. Data were obtained from wintertime sampling in Albuquerque-a time and location for which the two-source (motor vehicle, woodburning) aerosol carbon hypothesis is believed valid. Carbon isotopic tracers (C-14, C-12) provided a unique, absolute and direct means for tracing and quantifying fossil carbon and wood carbon contributions to the total aerosol carbon. Lead and mineral-corrected potassium served as unique, but indirect and uncalibrated (non-absolute) tracers for the two carbonaceous aerosol sources. Results for the two models showed excellent consistency for daytime carbon and good agreement for most samples, but the indirect tracer model underpredicted woodcarbon aerosol at night. Multivariate data exploration, including temperature as well as both elemental and organic (polycyclic) tracers suggested that the regression lack of fit, and excess nocturnal wood carbon were due to a third 'statistical'' component in the data. which in turn reflects a chemical non-linearity, apparently associated with volatility. Important conclusions from analysis of the combined isotopic, elemental and organic data from this study are that: (1) high molecular weight, condensed polycyclic hydrocarbons [benzo (ghi) perylene and coronene] appeared to be effective tracers for motor-vehicle carbon;and (2) at least two independent aerosol carbon components derived from woodburning, one of which-presumably involving volatile-to-aerosol carbon condensation-was uncoupled from elemental (K) tracer emissions from woodburning. Finally, some insight was gained into the process of characterizing urban and regional aerosol ''fingerprints'' on the basis of the observed variance-covariance structure of their isotopic and elemental composition. This was illustrated for the wintertime Albuquerque atmosphe
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