Modeling the operational oil spills from shipping in the Adriatic Sea

In the present work, we focus on chronic oil pollution from ships since even small amount of toxic oil compounds has immediate adverse biological effects. Moreover, routinely released hydrocarbons tend to cumulatively exceed volumes of the largest historical oil spills.

We perform stochastic simulations of virtual oil spills from ships in the Adriatic 2017–2020 applying the EMODnet vessel densities as a proxy for starting locations. MEDSLIK-II oil spill model is run using the high resolution (1/24 degree) currents and sea surface temperature provided by the Copernicus Marine Service and the ECMWF winds with a horizontal resolution of 1/8 degree.

Chronic exposure to operational oil spills is reported in terms of hazard indices for 5 vessel groups: (1) the pleasure and passenger ships that comprise ~47.2% of the total number of ships in the model domain; (2) cargo and service vessels with a contribution of ~24.2%; (3) fishing fleet with ~21.5%; (4) tankers with ~5.9%; and (5) remaining ships with ~1.2%.

The highest hazard indices from all ships are found in the northernmost part of the basin and along the coastlines of Italy, Croatia, and Slovenia. Near several major ports (Trieste, Koper, Venice, Split, Rijeka, Pescara, Brindisi, Durres, Zadar, Šibenik, and Dubrovnik), they are also elevated at the sea surface and on the coastlines. Conversely, the southern Adriatic exhibited the lowest values of hazard indices.

Comparative analysis of the integrals over the territorial waters of Italy and Croatia shows that the Croatian coastal waters are more chronically polluted than the Italian ones, despite their host less ships than the coastal waters of Italy. The reason for such an inconsistency is probably related to the differences in efficiency of circulation when the pollution from ships quickly dissipates along the Italia coast and tends to stagnate near the Croatian coast. Cargo and service ships are identified to be the main polluters in the Italian coastal waters. While in the Croatian coastal waters, most of the oil is received from the pleasure and passenger ships, particularly, from coastwise shipping. Offshore waters are found to be significantly less polluted than the coastal ones, with the main contribution from fishing, cargo and service vessels.

The results obtained can be considered representative of future events since the vessel density distribution and the amount of oil operationally spilled are assumed to be typical of the present state and not to change dramatically in the future. The historical meteo-oceanographic datasets 2017–2020 used are supposed to correspond to a realistic sample of possible weather and sea state conditions. The hazard indices computed can be used to improve the strategy of satellite and aerial surveillance, in-situ sampling, and ecotoxicological research in the Adriatic.

The presentation summarizes the results obtained in the framework of the FIRESPILL Project (Fostering Improved Reaction of cross-border Emergency Services and Prevention Increasing safety LeveL) funded under the Interreg V-A Italy-Croatia CBC 2014–2020 Programme (AP2–Security and Resilience).