PAHs and petroleum markers in the atmospheric environment of Alexandria City, Egypt

To evaluate the chemical fingerprint of hydrocarbons in airborne organic matter in the arid environment of Alexandria City, Egypt, the compositions of aliphatic and aromatic compounds were determined in suspended particulate material collected from a street undergoing heavy traffic in central Alexandria and in bulk deposition samples collected from a site representing an area increasingly influenced by human and industrial activities. Qualitative and quantitative characterizations of individual compounds were based on gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) analyses. More than 100 organic compounds are quantified in each sample, including n-alkanes, isoprenoids, polycyclic aromatic hydrocarbons (PAHs), sulfur-bearing heterocyclics, steranes/diasteranes, terpanes and aromatic steroids. The use of hydrocarbon profiles and ratios for identifying sources and processes is discussed. The molecular distribution of alkanes revealed that the main source of these compounds is from petroleum contamination with trace input of vascular plant wax. The PAH profiles, especially the relative abundance of alkyl-PAHs and sulfur-containing heterocyclics, showed that PAHs are chiefly derived from traffic sources. The results further indicated that diesel vehicles are more important PAH sources than gasoline vehicles. In addition, the source fingerprint of fossil fuel biomarkers such as steranes, terpanes and aromatic steroids agreed well with the fingerprint of unburned lubricating oil, which are probably contributed to vehicle exhaust emissions.