The Additivity and Stability of Carbon Signatures Obtained by Evolved Gas Analysis

Abstract

Evolved Gas Analysis (EGA) profiles are evaluated as a tool to classify carbonaceous aerosols for source apportionment studies. EGA is a method of characterizing carbonaceous aerosols according to their volatility. In this study the stability and additivity of EGA profiles were examined explicitly for the purpose of determining the applicability of EGA characterization to chemical mass balance techniques. Samples collected in a vehicle tunnel were subsequently exposed to particle-free (filtered) and particle-laden ambient air. The EGA profile did not change for tunnel samples exposed to filtered ambient air. By contrast, for tunnel samples exposed to particle-laden (unfiltered) ambient air, the resultant EGA profile was not the direct sum of the ambient and tunnel profiles. Specifically, the low-volatility carbon peak evolved at a lower temperature than the same peak in the unexposed tunnel samples. The change in evolution temperature was independent of carbon mass loading. Although evolution temperatures...