Target and Suspect Analysis with High-Resolution Mass Spectrometry for the Exhaustive Monitoring of PCBs and Pesticides in Posidonia oceanica Meadows and Sediments

This study enables the simultaneous monitoring of persistent organics pollutants (POPs) in the relevant marine seagrass Posidonia oceanica (L.) Delile (P. oceanica), without causing damage and preserving their ecological integrity and their key ecosystem services, and in marine sediments. Two classes of POPs that suppose a current threat to the environmental health status are investigated: polychlorinated biphenyls (PCBs) and pesticides. Comparisons between tissues and sediment compartmentation are studied for the first time. For these purposes, the sediments, P. oceanica leaves and, as a novelty, rhizomes, were studied. Samples were analyzed by gas chromatography coupled with high-resolution mass spectrometry (GC-Q-Orbitrap MS) for a comprehensive study. Eco-friendly methods were developed and validated for the determination of 38 POPs, 25 PCBs and 13 priority pesticides. The results showed that, when detected, regulated contaminants were localized mainly in the long-lived rhizomes, and 7 PCBs (the most abundant being PCB 44) and 4 priority pesticides (trifluralin, chlorpyrifos, isodrin and o,p’-DDT) were seen. Additionally, a retrospective analysis (suspect screening) was conducted, exhibiting up to 13 current-use pesticide residues in leaves and rhizomes alike. The results suggest that P. oceanica might be acting as a sink to contaminants in coastal areas and that rhizomes, due to their longer lifespan, reflect past and legacy contamination.