Occurrence of both nonvolatile and semivolatile carbonaceous air particulate markers using thermal desorption-pyrolysis-gas chromatography-mass spectrometry

Abstract

Particulate matter (PM) occurring in the atmosphere is a complex mix of organic species that originate from many sources due to long range transport. Many anthropogenic and biogenic sources have unique chemical components that enable their use as atmospheric markers of emissions. Application of thermal desorption–pyrolysis coupled with gas chromatography-mass spectrometry (TD-Pyr-GC-MS) enabled the characterization of both semivolatile and nonvolatile atmospheric markers in PM, both of which are difficult to characterize using traditional TD or solvent extraction alone. The nonvolatile organic PM fraction was found to be significant based on thermal optical analysis (TOA) quantification, with 73–87% of organic carbon (OC) evolving at temperatures above 400 °C (i.e., Pyr). The semivolatile organic carbon (SVOC) fraction (i.e., TD) of PM featured distinct profiles of alkanes, fatty acids, fatty acid methyl esters and 2-ring polycyclic aromatic hydrocarbons (PAHs), mostly associated with biogenic origin. By contrast, in the Pyr fractions of carbonaceous PM, highly abundant homologous series of n-alkenes, n-alkylbenzenes, PAHs, n-alkanes, and substituted phenols were identified. The occurrence of these compounds is conveyed through newly developed pyrolytic indicators reflecting the breakdown of biogenic sources, e.g., plant lipids, although certain sampling periods showed a contribution of anthropogenic origin. These previously unresolved biogenic and anthropogenic Pyr profiles provide a more representative characterization of atmospheric PM that can help in identifying emission sources.