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Emission source strengths of gasoline-filling processes determined by open-path spectroscopic techniques and inverse modeling

Up to now emission source strengths of diffuse and heterogenous emission of important VOCs are not well known especially from gas stations and gasoline tank farms. To estimate the total emission of these sources non-intrusive measurements were performed by a differential optical absorption spectroscopy (DOAS) system to determine the path- integrated concentrations of exhaust compounds downwind of the source through the whole exhaust plume. Simultaneously, the meteorological parameters were measured for modeling the dispersion of the plume inversely to obtain the emission source strengths of these compounds. The emissions by road traffic were determined by an additional open-path DOAS measurement. Measurement campaigns were performed during different wether conditions and at different sources which were characterized by well defined and easy air flow conditions. The emission source strengths were calculated with the Gaussian model PAL. The determined total emission of gas stations with gasoline vapor recovery system are about 20 mg benzene per kg refueled gasoline and the emission from refueling activities vary between 1 and 9 benzene per kg refueled gasoline depending on the technical behavior of the gasoline vapor recovery system. These values which were found from measurements during times with a and without refueling activities show a high amount of diffuse emissions. The emission rates from a gasoline taken farm were measured on an open path through the middle of that area and a maximum of 8 (mu) g/(m2s) was determined.