Persistence and sources of polycyclic aromatic hydrocarbons in mangrove sediments of the Tinharé-Boipeba Archipelago (Brazil) two to four years after the 2019 oil spill.

内容摘要

The Tinharé Archipelago (TA), located within an Environmental Protection Area (Bahia, Brazil), is a largely preserved mangrove area. Despite this, it is subject to frequent anthropogenic activities, notably the 2019 oil spill that impacted the Brazilian coastline. This study assessed the concentration of Polycyclic Aromatic Hydrocarbons (PAHs) in sediments collected from three estuaries within the TA islands (Boipeba, Garapuá, and Morro de São Paulo) and evaluated temporal changes in contamination levels. Surface sediments were collected at seven points within each estuary in August 2021 and August 2023. Samples were extracted using organic solvents via an Accelerated Solvent Extraction system. Quantification of the 16 priority PAHs was performed using gas chromatography coupled with mass spectrometry. Total PAHs concentrations ranged from 33.5 to 5746 ng g-1. Garapuá exhibited moderate to high concentrations, while contamination levels in the other areas ranged from low to moderate. Diagnostic ratios suggested shifts in contamination sources, although their interpretation is subject to limitations in weathered sediments. Garapuá (2023) exhibited signatures consistent with petrogenic inputs, possibly associated with weathered oil residues, whereas Boipeba (2021) and Morro de São Paulo (2023) may be contaminated by petroleum combustion sources. Pyrogenic signals from biomass burning were more prevalent Morro de São Paulo (2021) and Boipeba (2023), suggesting local human activities. Despite regional conservation efforts, the persistence of oil-derived PAHs underscores the lasting environmental impact of oil spills. These findings indicate the persistence of petroleum-related contamination in tropical mangrove systems, although the specific contribution of the 2019 oil spill cannot be unequivocally established using PAHs data alone. Continued monitoring is essential to understand contaminant dynamics and guide protection strategies.