Key points are not available for this paper at this time.
Radiocarbon (14C) analyses of PM2.5 (particulate matter with an aerodynamic diameter of 2.5 μm or less) of both ambient and source samples from the Northern Front Range Air Quality Study (NFRAQS) in Colorado were performed. The 14C analyses were undertaken to provide direct fossil vs modern (biomass) carbon source discrimination data for a subset of summer and winter 1996−1997 samples collected within the Denver metropolitan area. Samples were prepared for 14C accelerator mass spectrometry measure ments using techniques specially developed for small samples, i.e., <100 μg C. For the days and sampling periods analyzed the median and interquartile range of the winter blank corrected fraction of modern carbon was 23% (16−34%) at Welby and 27% (25−37%) at Brighton. The summer samples exhibited a more mixed signature with a median and interquartile range of 47% (9−70%). Source samples yielded 14C signatures consistent with expectation. We conclude fossil-derived sources contribute substantially in both seasons and at both locations; however, the biomass carbon component dominates episodically in the summer.
Klinedinst et al. (Wed,) studied this question.