Temperature-induced volatility of molecular markers in ambient airborne particulate matter

摘要: Abstract. Molecular markers are organic compounds used to represent known sources of particulate matter (PM) in statistical source apportionment studies. The utility molecular depends on, among other things, their ability PM volatility under realistic atmospheric conditions. We measured the particle-phase concentrations and temperature-induced commonly-used California's heavily polluted San Joaqin Valley. Concentrations elemental carbon, levoglucosan, polycyclic aromatic hydrocarbons were not reduced by mild (~10 K) heating. In contrast, both hopane/sterane n -alkane reduced, especially during summer sampling events at urban site. These results suggest that hopanes steranes have effective saturation ~1 μg m −3 , therefore can be considered semi-volatile. an individual compound on its inherent properties (primarily vapour pressure) interactions between itself any potential absorbing phase. behavior -alkanes is consistent with predicted for absorption suberic acid (a C 8 diacid) using a group contribution modelling method. Observations also matched absorbent whose composition based recently-obtained high-resolution aerosol mass spectrometer factors (approximately 33% "hydrocarbon-like" 67% oxygenated aerosol). evaporation -alkanes, hopanes, heating rural and/or winter experiments could explained more phase along non-absorptive partitioning mechanism, such as adsorption soot. This suggests large most important if relatively non-polar exists. While activity coefficients may close unity, assumption ideality (e.g., hopanes) result errors calculations.