Occurrence, source apportionment, and nutrient correlations of petroleum hydrocarbons in coastal sediments of Xiaogan Island, China

Petroleum hydrocarbon (PHC) pollution in coastal environments is a critical ecological concern, yet its biogeochemical interaction with sedimentary nutrients remains underexplored. This study investigated the occurrence, source apportionment, and environmental correlations of alkanes and polycyclic aromatic hydrocarbons (PAHs) across 36 sediment samples from the intertidal, supratidal, and subtidal zones of Xiaogan Island, China. Results indicated generally low pollution levels (Class I marine sediments), with total alkanes (0.015–155.08 μg/g dw) and PAHs (0.011–688.80 ng/g dw) exhibiting localized enrichment in surface and intertidal sediments. Diagnostic ratios revealed a highly complex, mixed-source profile encompassing marine, terrestrial, natural, and anthropogenic inputs with limited long-range transport. Crucially, while PHCs and nutrients lacked significant linear correlation , Redundancy Analysis (RDA) uncovered non-linear clustering mechanisms, separating NO3⁻/SO4²⁻ and NH4⁺/PO4³⁻ into distinct interactive groups. These findings challenge conventional linear assessment models, providing an innovative baseline for regional environmental management and offering new perspectives on the complex behaviors of PHCs in coastal mudflats.