Comparison of fluorometric signatures of oil residues in both marine environment and in organic diluent

The significant part of petroleum substances is transferred to the marine environment after technical activities (inevitable exploitive spills, illegal discharges). However a certain part of petroleum in seawater coming from the natural sources. Therefore, to develop the safety of natural marine environment it is necessary to track not only the anthropogenic pollutants but also the natural sources of petroleum. To distinguish both source of oil the fluorescence properties of oil can be used as the tools to oil identification. The aim of the study is to describe the optical properties of crude oil after it contact with aquatic environment based on fluorescence spectroscopy. For the study, crude oil ‘Petrobaltic’ type potentially found in marine environment due to coming from natural source was applied. To dissolve oil, two different solvent – hexane and Baltic seawater form the Gdynia coast were used. To measure the excitation-emission spectra (EEMs) of oil spectrofluorometer Hitachi F-7000 FL was applied. In the paper, we discuss the changes of oil EEMs in two cases for oil dissolved in n-hexane and for oil dissolved in seawater for various oil concentration. Obtained EEMs for oil dissolved in seawater indicate that EEMs spectrum contain the main peak – describing by the wavelength – independent fluorescence maximum, which was detected for oil dissolved in n-hexane (typical for this kind of oil). However, the intensity of oil fluorescence decreases after oil contact with seawater. This approach could allow expanding the description of complex mixtures of oils as a possible tool proposed for identification the type and origin of oil found in marine environment.