Modelling the influence of thermal stratification and complete mixing on the distribution and fluxes of polychlorinated biphenyls in the water column of Ispra Bay (Lake Maggiore)

A 1D coupled hydrodynamic and contaminant fate model was applied to simulate the distribution of polychlorinated biphenyls (PCBs) in the Ispra Bay located in the southern part of Lake Maggiore (Italy). The model succeeded in representing the hydrodynamic processes occurring in the lake such as thermal stratification during summer 2005 followed by the complete mixing of the water column in February 2006. The results of the PCB fate model highlighted that these processes play a key role for the settling of particles and consequently for the distribution of PCBs in the water column as well as for the contaminant flux at the sediment–water interface. On the air–water front, the simulations emphasised that the net atmospheric PCB input fluxes are generally more important during the cold season and show peaks during periods of high wet deposition. Finally, the seasonal variability of the distribution of PCB in the water column was assessed.