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Sunken oil mats (SOMs) pose a significant threat to marine ecosystems, yet their long-term fate and weathering processes remain poorly understood. This study investigates the degradation of biomarkers in a SOM sample collected from the Brazilian coast following the long-lasting 2019 oil spill. The SOM clearly distinguished from spilt oil and were attributed to tanker-washing residues. Analysis of its sections revealed a consistent depletion pattern, associated with losses of volatile and photooxidation-sensitive compounds, even in the most preserved inner fractions, this suggests weathering of the oil prior SOM formation. While biodegradation was minor, photooxidation revealed a significant weathering factor, especially for aromatic compounds as indicated by preferential degradation of highly-alkylated tricyclic aromatic sulfur heterocycles, and specific methylpyrenes and benzofluorenes. This study underscore the complex interplay of weathering processes shaping the fate of SOMs and the importance of biomarker-based diagnosis in assessing the origin and ecological impacts of long-lasting oil spills., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study provides an overview of the evaluation of polycyclic aromatic hydrocarbons (PAHs) in the coastal regions of Santos Basin, located in Brazil's Southeast region, the country's most industrialized area. The analysis is based on data compiled from various studies in this area since 2000. A comprehensive literature review was conducted using the SCOPUS database, encompassing peer-reviewed scientific journals from publishers such as Elsevier, Springer, Nature, Wiley, Taylor & Francis, Google Scholar, and ResearchGate. Most of these studies have focused on the sediment compartment due to its role as the primary repository for organic matter and, consequently, PAHs in the marine environment. However, the bioavailability of organic contaminants in sediment is generally lower compared to water and suspended particulate matter, which has received less attention in the context of Santos Basin. The literature search also includes studies evaluating PAH concentrations in organisms to investigate the bioaccumulation rates of these compounds. Data presented in this review primarily originates from coastal and estuarine areas within Santos Basin, with occasional extensions to the continental shelf. The majority of publications are centered on studies conducted in the southeastern Brazilian states of São Paulo and Rio de Janeiro, where the highest levels of PAH contamination across all environmental compartments are typically observed. Santa Catarina, on the other hand, is the coastal region with fewer studies. The regions where most of the studies involving PAHs in the Santos Basin are concentrated in areas where public university research centers are located, a pattern that repeats throughout the Brazilian coast. In areas far from universities, little is known about the environmental status of PAHs., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This review delves into the intricate world of Polycyclic Aromatic Hydrocarbons (PAHs) and their bioaccumulation in marine organisms. It explores how physicochemical attributes of individual compounds, along with metabolic oxidation and elimination processes, influence this bioaccumulation. The review further investigates the risks and toxicity associated with PAHs in marine organisms. Subsequently, sediment and water quality guidelines used to assess the potential for adverse effects from PAH exposure are discussed exposing significant differences in the methodological approaches used to establish the guidelines, which can lead to discrepancies in the values used to compare PAH concentrations and limitations to their use. Emphasis is placed on the criteria employed in establishing these guidelines, rooted in adverse effects data linked to PAHs, and efforts to establish local quality guidelines for a tropical area are described. This exploration serves to enhance our understanding of the complex interplay between PAHs and marine ecosystems, informing more effective environmental management strategies., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)