Non-methane hydrocarbons (NHMCS) variability in the Eastern Mediterranean

Non-methane hydrocarbons (NMHCs) are important constituents of the atmosphere that contribute both to the oxidation capacity of the atmosphere and to the formation of the secondary organic aerosol. In Europe, over the last decades, many efforts have been devoted to the assignment of NMHCs sources and although NMHCs role is well established large uncertainties in their emissions still exist. Measurements of NMHCs in the atmosphere of the Eastern Mediterranean are very scarce in the literature and, therefore, the present work is willing to provide an assessment of individual NMHCS sources on both spatial and temporal basis in the Eastern Mediterranean. Intensive campaigns of several days took place each month by in situ continuous hourly measurements of NMHCS from C-2 to C-8 in different locations on the island of Crete, Greece (marine, rural and urban areas). All samples were analysed for 45 HMHCS with a gas chromatographic (GC) system equipped with a flame ionisation detector (FID). A simple statistical analysis of the relationship between various hydrocarbon pairs indicates influences from common sources. The average measured hydrocarbon concentrations show seasonal variations in agreement with previous published measurements. Evidence for both chemical processing and source dominating the variability of NMHCs mixing ratios were obtained. Chlorine atom concentrations were indirectly derived from changes in the patterns of the measured NMHCs. The result of the present study suggests that the Cl-atom induced reaction may be as well of considerable importance in the troposphere of the region.