PAHs in Sediments from Amazon Mangrove and Oyster Farming Areas: Sources, Ecological Risks and Potential Toxicity

Area of Science:

• Environmental Chemistry
• Marine Biology
• Ecotoxicology

Background:

• Mangrove ecosystems are vital interfaces between terrestrial and marine environments.
• Polycyclic Aromatic Hydrocarbons (PAHs) are persistent organic pollutants with diverse anthropogenic and natural sources.
• Assessing PAH contamination in Amazonian mangroves is crucial due to their ecological and socioeconomic importance.

Purpose of the Study:

• To quantify sixteen polycyclic aromatic hydrocarbons (PAHs) in mangrove sediments across three Amazonian municipalities.
• To identify and apportion the sources of PAH contamination.
• To evaluate the ecological risks associated with PAH levels and potential transfer to oysters.

Main Methods:

• Sediment sampling from three Amazonian municipalities (Curuçá, Augusto Corrêa, Salinópolis).
• Quantification of sixteen PAHs using analytical chemistry techniques.
• Source apportionment using diagnostic ratios and multivariate statistical analysis.
• Toxicity assessment using carcinogenic equivalents and ecological risk indices.

Main Results:

• ∑PAH concentrations ranged from 4.55 to 1303 ng g⁻¹ dry sediment, indicating low to moderate contamination.
• PAH levels were highest in Curuçá, followed by Salinópolis, and lowest in Augusto Corrêa.
• Estimated sources: 30% fossil fuel combustion, 59% biomass/coal burning, 11% petrogenic/natural.
• Dibenzo[a,h]anthracene exceeded ecological risk thresholds in Curuçá and Salinópolis.

Conclusions:

• Biomass/coal burning is the dominant source of PAHs in the studied Amazonian mangroves.
• While overall carcinogenic toxicity is low, specific PAHs pose ecological risks in certain areas.
• There is a potential risk of PAH transfer from suspended sediments to oysters, particularly in Curuçá and Salinópolis.