Properties of the Baltic crude oil in the oil-in-water emulsion form : excitation-emission spectra

Due to the fact that marine environment contamination by oil substances are not uncommon, it is necessary to improve the ability of determine their origin. Therefore, research on the possibility of recognizing the type of oil using its individual characteristic manifested in the processes of fluorescence excitation has been undertaken. Oil pollutants present in seawater mainly coming from ship drives, tankers, pipelines or sea bottom seeps, moreover oil leaks from offshore extraction equipment also are possible. For this reason, the crude oil extracted from the Baltic Sea deposit in the Polish Maritime Areas has been chosen for tests. Fluorescence properties of water containing small amounts of oil (concentrations from 5.59 to 55.4 ppm) in the form of oil-in-water emulsion were tested. Individual samples were assigned matrices of fluorescent values for different wavelengths, while excited by monochromatic light also for different wavelengths. The obtained matrices were visualized as a contour maps and 3D charts. For considered concentrations of crude oil dispersed in water, the wavelength-independent fluorescence maximum was determined. Obtained result indicates that in the studied wavelength range, the total fluorescence intensity is proportional to the oil concentration only for the lowest oil concentrations. The analysis of the objective parameter of the difference between the shapes of spectra indicates the similarity of the spectral shape for the lowest oil concentrations. These results are the methodological suggestion, that for the purpose of identifying the type of oil dispersed in water, spectra should be determined for sequences of different dilutions, until the excitation-emission spectra shapes become independent from the oil concentration.