C to C hydrocarbon measurements in the two largest 3 9 cities of Greece, Athens and Thessaloniki. Calculation of hydrocarbon emissions by species. Derivation of hydroxyl radical concentrations

Non-methane hydrocarbon concentrations ŽNMHC. were determined in samples collected in electropolished canisters aboard a Falcon aircraft in Athens and Thessaloniki. Some canisters were also collected on the ground in Athens. Chemical analysis by cryoconcentration permitted the speciation of NMHC. The aircraft samples allowed the determination of the background concentrations in the periphery of each city. Concentration ratios were compared with other European cities. The aromatic hydrocarbon fraction dominates the measured species. Using the simple box model modified to account for the chemical destruction of each hydrocarbon, the emissions for each species were determined in Athens and Thessaloniki. The hydroxyl radical concentrations were calculated using hydrocarbon concentration ratios in the urban areas and at a downwind distance.