VOC emission source strengths of tankers during refuelling activities determined by spectroscopic remote sensing and inverse dispersion modeling

ABSTRACT Tankers are a wide spread and important emission source of VOC’s. Up to now emission data are available frommeasurements inside the storage tanks to investigate explosion protection only. Different emission reduction systemsare under discussion such as vapour recovery units. The environmental impact of these alternatives shall beinvestigated.The VOC emissions of tankers were investigated in a river harbour. Fence-line monitoring by Differential OpticalAbsorption Spectroscopy (DOAS) was performed to investigate different emission sources during activ ities of tankersin harbours. Benzene, toluene and p-xylene concentrations were measured by a mono-static DOAS using 3 retro-reflectors. The inverse method was applied on the basis of these non-intrusive measurements of effluent concentrationsin the exhaust plume and meteorological measurements to determine the emission source strengths. Inversion ofeffluent's dispersion was performed by a Lagrangian model driven by wind fields of the Eulerian model MISKAMconsidering influences from buildings and the orography upon the streaming fields.The emission source strengths were determined from unloading and loading of gasoline, from ventilation of storagetanks of tankers into ambient air which is of common practice if the tankers are operated without load or if the tankersare to be refuelled with a different product than before and from using the land-site gasoline vapour recovery unit in atank farm for ventilation.Keywords: Differential Optical Absorption Spectroscopy, Fourier Transform Infrared Spectrometry, VOC, benzene,fence-line monitoring, emissions of tankers, ventilation of storage tanks, unloading of gasoline, emission sourcestrengths, inverse dispersion modelling