The role of sea surface circulation and weather dynamics in the PAH contamination in coastal mussels. A case study in the Southern Tyrrhenian sea

The Gulf of Pozzuoli, a marginal sub-basin of the Tyrrhenian Sea, has a longstanding tradition of bivalve mollusk farming. Despite its historical importance, the area faces significant anthropogenic pressures, particularly from the decommissioned industrial site at Bagnoli. Seasonal monitoring data indicate peaks in mussel contamination by polycyclic aromatic hydrocarbons (PAHs) in late autumn and early winter. This study analyzed the oceanographic and meteorological dynamics driving PAH contamination in 2016, when elevated PAH concentrations were recorded at one farming site. A combination of in situ measurements, satellite observations, numerical model outputs, and Lagrangian simulations was used to examine sea surface circulation, wind patterns, wave dynamics, and particle transport pathways. Contamination events were consistently preceded by approximately one week of northwestward surface currents, likely facilitating pollutant transport from Bagnoli to the farming area. Southerly waves exceeding 1.2 meters in height and periods longer than 8 seconds were recorded prior to contamination peaks, suggesting wave-induced resuspension of PAHs from sediments. These hydrodynamic conditions coincided with prevailing southwesterly winds. The findings support the hypothesis that specific meteorological and oceanographic conditions enhance PAH transport from Bagnoli to the mussel farms, posing risks to aquaculture and public health. Based on previous and current data, the study provides robust conclusions on PAH pollution in the Gulf of Pozzuoli and offers a rationale for improving monitoring and management strategies to mitigate contamination risks in vulnerable coastal areas.