Cruise ships flow rate emission evaluated by means of a passive DOAS instrument

The emissions of the cruise ships, in terms of nitrogen dioxide (NO2) and sulphur dioxide (SO2), are evaluated with the DOAS scanning spectrometer TropoGAS (Tropospheric Gas Analyser Spectrometer) developed at ISAC CNR in close collaboration with the CGE-UE. The slant columns amounts of the above mentioned compounds are obtained with the application of the Differential Optical Absorption Spectroscopy (DOAS) technique to the spectral measurements carried out with the TropoGAS instrument. This last is linked with an optical fibre to a simple scanning optical system allowing for measurements in multiple axis configurations. The measurements are carried out across the Giudecca Channel in Venice, during two field campaigns performed in July and in October 2007. The instrumental setup, the DOAS method and the technique for the evaluation of the ships emissions, are described. The results of flow rate emissions for NO2 and SO2 are presented and discussed. Their mean values are about 12g/s and 4 g/s for NO2 and SO2 respectively.