Tracing oil spill contamination in coastal and estuarine ecosystems using δ ¹³ C and Δ ¹⁴ C isotopes: A review

Abstract Oil contamination in estuarine and coastal ecosystems presents major challenges for environmental monitoring due to the complex mixture of organic matter from biogenic and petrogenic sources. This review synthesizes recent advances and limitations in the combined use of carbon isotopes δ 1 3 C and Δ 14 C to trace petroleum contamination in marine sediments. Sixteen empirical studies were analyzed to evaluate the effectiveness of this dual-isotope approach in identifying fossil carbon, estimating its degradation state, and assessing its environmental persistence. While δ 1 3 C provides insights into organic matter sources and transformation, Δ 14 C offers a sensitive tracer for detecting fossil carbon inputs, even in low concentrations or mixed matrices. The review highlights how their integration strengthens source attribution and enhances the resolution of hydrocarbon monitoring in dynamic coastal settings. An exploratory typology based on Δ 14 C and F m is proposed to semi-quantitatively classify contamination severity and support cross-study comparisons. Despite its potential, the approach faces challenges such as high analytical costs, limited laboratory access, and a lack of methodological standardization. Future efforts should focus on integrating compound-specific isotope analysis, expanding applications in mangrove ecosystems, and refining interpretative models to improve the forensic utility of carbon isotopes in oil spill investigations. This review contributes to the systematization of isotopic methods in environmental forensics and reinforces their role in tracing petroleum-derived carbon in sensitive coastal environments.