Environmental hazards, risks, and management options of in situ burning residues from oil spills: A systematic review and future perspectives

In-situ burning (ISB) represents a rapid and operationally efficient method for responding to marine oil spills, although the environmental consequences of its residues remain incompletely understood. This review synthesizes existing evidence on the composition, fate, and effects of ISB residues, with particular focus on the understudied processes of marine oil snow (MOS) formation and benthic deposition. ISB residues differ chemically from parent oils, typically showing enrichment in higher-molecular-weight and oxygenated compounds. However, substantial uncertainties persist concerning their environmental persistence, transport dynamics (including sinking, resuspension, and integration with MOS), and ecotoxicological impacts on pelagic and benthic organisms. These knowledge gaps are exacerbated by the scarcity of standardized sampling and toxicity testing protocols, which often fail to adequately capture particle-mediated exposure pathways. We propose a three-part framework: (i) multi-temporal remote sensing imagery for residue detection and early warning systems; (ii) high-resolution chemical characterization extending beyond parent polycyclic aromatic hydrocarbons (PAHs), coupled with standardized water-accommodated fraction (WAF) and particle-associated toxicity assays; and (iii) fate and transport models tailored to incorporate ISB residue parameters for operational applications. Standardization of analytical methods and model parameters with existing regulatory frameworks will enable quantitative trade-off analyses between atmospheric emissions and subsurface/benthic contamination risks. Ultimately, this framework elucidates scenarios in which ISB may alleviate acute dissolved-phase exposures while potentially redirecting risks toward chronic, sediment-associated pathways, thereby advancing evidence-based strategies for sustainable oil-spill response.