IVL Swedish Environmental Research Institute

The report summarizes the results and conclusions from environmental monitoring of coastal meadows and stranded macroalgae/seagrass following the grounding of the RORO vessel Marco Polo in Pukaviksbukten on 22 October 2023, which resulted in a major spill of approximately 150 tonnes of heavy fuel oil (HFO). The investigation was conducted by IVL Swedish Environmental Research Institute on behalf of the County Administrative Board of Blekinge, with the aim of assessing the remaining levels of oil contamination in coastal soils and stranded macroalgae/seagrass, as well as evaluating temporal changes in contaminant concentrations within the algal/seagrass material. Sampling was performed in both oil-exposed and reference areas during the period 2024–2025. The analyses included BTEX, PAH16, alkylated PAHs, and TPH, with a particular focus on polycyclic aromatic compounds (PACs) as indicators of oil pollution. Soil samples were collected at three depth intervals from the sites Rökemarken, Lörbykladd S, Spraglehall N, Spraglehall S, and Furumo (reference site), while stranded macroalgae/seagrass samples were collected from Djupekås, Töppet, Lörbykladd S, Spraglehall N, Spraglehall S, and Torhamn (reference site).

All analyses were performed by an accredited laboratory (ALS Scandinavia AB). The results demonstrate a heterogeneous distribution of oil contamination along the coastline. The highest concentrations in soil were detected at Spraglehall N, where levels of heavy PAH compounds (PAH-H) in the upper soil layer (0–15 cm) exceeded the Swedish EPA limit value for sensitive land use (KM) by up to sevenfold. Other sampling sites exhibited lower, yet elevated, concentrations. Deeper soil layers (15–25 cm) generally showed low contaminant levels. Oil residues were detected in stranded macroalgae/seagrass at all sampling sites, with the highest initial concentrations at Töppet (38.7 mg/kg wet weight). A decline in concentrations was observed over time, except at Djupekås where levels increased between 2024 and 2025, suggesting continued deposition of oil-contaminated algal/segrass material. The contaminant profiles were dominated by alkylated PAHs. Despite extensive remediation efforts, the oil spill continues to affect the coastal ecosystem in Pukaviksbukten. Contaminant levels at Spraglehall N pose a potential risk to grazing livestock and may contribute to secondary contamination of surrounding environments. Continued long-term environmental monitoring is recommended, particularly at Djupekås and Spraglehall, as well as improved integration between remediation measures and environmental follow-up to enhance understanding of pollutant persistence and ecological impacts.