Fluorescence of natural seawater exposed to oil pollution

The natural seawater contains both dissolved and suspended organic substances originating from natural sources and human activities – like the marine transport fleet among other. To specify the type and quantity of vitally valid as well as dangerous for properly functioning marine ecosystems substances complicated and sophisticated chemical instrumentation and methodologies must be used. Only a small number of seawater components it is possible easily to determine their concentrations – for example, the salt content is determined directly in the bulk of water through simultaneous measurement of electrolytic conductivity and temperature of water. It is worth to search similarly quick method for oil substances directly in the seawater. Taking into account seawater organic pollutants originating from natural sources inter alia crude oils, the presence of refinery petroleum substances due to their fluorescence in ultra-violet light can be determined based on fluorescence spectroscopy. The aim of this paper is to search fluorescence features of oil substances dissolved in natural seawater based on excitation-emission spectroscopy. In the paper fresh and oily contaminated seawater taken from the coastal area of the Baltic Sea were used. As an oil pollution ‘Petro-baltic’ oil were applied. The natural seawater, at first was laboratory exposed to low extremely amount of oil and then it was examined by fluorescence under UV light. The seawater from vicinity of Gdynia (Poland) were tested as fresh and after artificially contaminated by different amount of oil (from 0.5 to 500 ppm). Spectrofluorometer Hitachi F-7000 FL was applied to measure excitation-emission spectra (EEMs). Low amounts of oil (up to several ppm) cause increasing of main peak in excitation-emission spectra (EEMs). Addition of larger amounts of oil results in appearance new peaks, which originate from fluorescence of soluble fractions of oil artificially added to examined water. These specific features of oil describe the spectroscopic signatures of oil, which is the basis to development operational method of the source of oil pollution identification.