Past and present contaminants in sediment samples collected from Bizerte lagoon and inflowing rivers, Tunisia: Occurrence and potential risks.

The aim of the present study was to conduct an exploratory survey of legacy persistent organic pollutants and emerging compounds in sediment samples from Bizerte lagoon and its inflowing rivers to determine contamination patterns according to anthropogenic activities carried out in the area. Compounds studied included organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), organophosphorus flame retardants (OPFRs), organophosphorus pesticides (OPPs), phthalates, alkylphenols (APs), bisphenol A (BPA) and nicotine. Almost all the targeted compounds (54 out of 59) were detected in the 15 sediments analyzed. ∑PAHs were predominant and ubiquitous in both Bizerte lagoon and river sediments, with average concentrations between 210 ± 186 and 159 ± 64.4 ng g dw, respectively, and the preliminary diagnostic ratios and multivariate analysis showed the predominance of PAHs of pyrolytic origin. PCBs (5.55 ± 3.28 and 6.57 ± 4.06 ng g dw, in Bizerte lagoon and river sediments, respectively) and DDTs (2.72 ± 3.40 and 5.42 ± 2.97 ng g dw), despite being forbidden, were widespread but detected at trace concentrations and reflect their past use in Tunisia. ∑OPFRs (2.91 ± 4.32 and 7.28 ± 7.17 ng g dw), and BPA (0.65 ± 0.82 and 1.30 ± 1.06 ng g dw) were the least detected compounds, while APs and phthalates were only punctually quantified both in sediments from the Lagoon (OP, DMP, DiBP and DEHP) and rivers (OP, DEP and DiBP). The use of Sediments Quality Guidelines (SQGs), Toxic Equivalent Factor (TEF) and the Risk Quotient (RQ) revealed that among the 7 categories of micropollutants studied, pesticides and PAHs were the substances that posed the highest environmental risks to aquatic organisms (fish, invertebrates and algae) in surface sediments of Bizerte lagoon and inflowing rivers. The research highlights a pressing need for stricter and long-term monitoring to allow regulatory control over chemical use and disposal to protect aquatic life.