Source Apportionment of n-Alkanes and Polycyclic Aromatic Hydrocarbons (PAHs) in Surface Sediments of the Makuran Coast (Sirik-Jask), Gulf of Oman: An Integrated Biomarker Approach

Introduction: Rising hydrocarbon pollution in coastal sediments raises environmental concerns, but biomarker-based evaluations are still lacking in the Makuran area. Growing industrial development along the Sirik–Jask coastline, including port expansion and petrochemical projects, has raised alarm over sediment pollution, but the origins and extent of hydrocarbon inputs remain largely unknown. Methods: In this study, surface and intertidal sediment samples were collected from five stations along the Sirik-Jask coast. The samples were freeze-dried, homogenized, and extracted using Soxhlet for n-alkanes (C12-C34) and polycyclic aromatic hydrocarbons (PAHs), followed by GC-MS analysis. Also, Molecular diagnostic ratios and distribution patterns were applied to identify the origin of hydrocarbon pollutants. Results: n-Alkane concentrations ranged from 3967.48±1290.71 to 28676.33±4046.17 (μg/g dw), while PAHs ranged from 1143.35±156.11 to 8059.95±656.15 (ng/g dw), classifying most stations as highly contaminated. Intertidal sediments consistently accumulated higher hydrocarbon burdens than adjacent coastal zones. Low molecular weight PAHs accounted for over 80% of the total PAH burden, and diagnostic biomarker ratios across all samples converged on a predominant petrogenic origin for sedimentary hydrocarbons throughout the study area. Conclusion: According to established sediment quality guidelines, most stations showed high levels of contamination. This research provides the initial biomarker-based baseline information on hydrocarbon pollution in Makuran coastal sediments. The results reveal the region’s exposure to oil-derived contaminants and reinforce the importance of continuous environmental monitoring and strategic mitigation efforts to preserve marine ecosystems.