Year-Round Testing of Coastal Waters of the Gulf of Gdańsk in the Baltic Sea for Detecting Oil in a Seawater Column Using the Fluorescence Method

Progressive climate changes and the increase in the occurrence of extreme weather phenomena indicate the need to take action to mitigate the negative effects of climate change. One of the main factors affecting climate change is the state of waters that transport heat. Oil pollution present in the water contributes to the absorption of radiation and physico-chemical changes in the sea, which has an impact on the marine ecosystem. This indicates the need to develop methods for effective oil spill detection. This study aimed to improve the methods of early detection of threats related to oil spills in the marine environment, especially when the source of oil may be invisible in the depths of the sea. Therefore, the method based on the fluorometric index is proposed, and its effectiveness for oil detection in seawater is studied. The study has answered the question of how biological activity during a whole year influences the effectiveness of oil detection by the proposed fluorometric index method. Therefore, for the calculation of the fluorometric index, the changes in the seawater fluorescence spectrum in the ultraviolet range were determined, which occurred under the influence of diffusion of some oil components in the sea. The principle of detection of oil contaminants based on the excitation-emission fluorescence spectrum is described. For the measurements, natural seawater samples used in the laboratory were exposed to a mixture of crude oil and oils commonly found in navigation. The effectiveness of oil substance detection using the fluorometric index in the biologically productive and unproductive seasons was analyzed for seawater in the vicinity of Gdynia and Gdansk ports in Poland in northern Europe. The results of excitation-emission spectra and fluorometric index indicate that the changes in the biological activity during the year do not affect the detectability of oil present in seawater for the considered oil-to-water ratio. Summarize the sensitivity analysis of the method indicates the possibility of detection of oil contamination regardless of the season. The obtained results pave the way for the construction of an underwater device to detect oil in the vicinity of such a detector.