Very low sulfur fuel oil spilled from the MV Wakashio in 2020 remains in sediments in a Mauritius mangrove ecosystem nearly three years after the grounding.

The oil spill resulting from the grounding of the MV Wakashio on a reef off the coast of Mauritius in July 2020 was the world's first major spillage of Very Low Sulfur Fuel Oil (VLSFO) since the implementation of a Global Sulfur Cap from January 2020. In this study, we examine sediments collected in March 2023 from two Mauritius mangrove systems. Analyses by both gas chromatography-mass spectrometry and comprehensive two-dimensional gas chromatography confirmed, by comparison of molecular biomarkers, the presence of Wakashio VLSFO in one of the mangrove systems. The spilled oil had undergone extensive weathering resulting in substantial losses of toxic mono- and polycyclic aromatic compounds. Applying WebGNOME-ADIOS oil spill models to compare the fate of Wakashio VLSFO with traditional fuels suggests that more of the VLSFO would evaporate, naturally disperse, and undergo sedimentation compared to traditional fuels that were more likely to remain floating.