Source Apportionment of Particulate-PAHs Using 13C Molecular Isotopic Approach
Résumé
Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous organic compounds widely found in all environmental compartments. The main concern of PAHs is that some of them are reported to have carcinogenic and mutagenic properties. In the atmosphere, they are mainly emitted as by-products of organic matter and fossil fuel incomplete combustion such as, domestic heating, automobile fuel combustion, wood burning and other industrial processes. Once released into the atmosphere, they are present on both gaseous and particulate phases and may be submitted to photodegradation and/or chemical oxidation by O3, OH or NOx. In order to differentiate and apportion PAH sources, several approaches of source assessment are proposed in the literature like, for instance, the molecular PAH concentration ratios. Recently, the use of 13C molecular isotopic composition has been developed to improve the molecular approach, commonly used to characterize atmospheric particulate-PAH sources. The first step of the method consists in measuring the 13C/12C isotopic composition of particulate PAHs from specific sampling sites (urban, rural, traffic), well characterized emissions (ship soot, kerosene burner, coal fly ash...) or reference materials (urban dust, diesel soot) . It is important, in a second step, to check the influence of atmospheric physico-chemical processes on the PAH isotopic composition values such as the heterogeneous reactivity with atmospheric oxidants, photolysis and particle transport. In this work, will be presented and discussed the last results of our group on the use of molecular isotopic composition as an interesting source tracer of atmospheric particulate-PAHs, 13C/12C PAH ratios being measured by using gas chromatography/combustion/isotopic ratio mass spectrometry (GC/C/IRMS).