Numerical modelling of pollutant fluxes between environmental segments

This doctoral dissertation focuses on numeric modelling of sediment resuspension and transport as well as pollutant fluxes between the sediment, water and air. These processes are an important part of the mass balance of the sediments and pollutants in the aquatic environment. Sediment resuspension is influenced by sea currents and waves, in shallow bays also by maritime traffic. We developed a new model that calculates shear velocities at the sea bottom using information on navigation and the ship's characteristics. The existing three-dimensional mathematical model PCFLOW3D was upgraded with the interface to couple with the wave model SWAN. With it we performed numerous simulations in which we combined different sediment resuspension forcing factors: currents, waves, and navigation. The simulation results show that the most important factor in ordinary meteorological conditions is navigation since the bottom shear velocities were locally by an order of magnitude higher than the ones caused by other forcing factors. With the new model it is also\ud possible to estimate the influence of different vessels on the bottom. In addition we measured the suspended sediments / studied the hysteresis effect on the river Idrijca and tried to estimate the transportation of mercury in the catchment of the Idrijca and the Soča towards the Gulf of Trieste. However, no reliable results could be obtained due to several organisational difficulties. With the use of the improved Gårdfeldt method and GEM we calculated the annual evasion of mercury in the Mediterranean Sea. The obtained high results compared with the results of other studies show that either the processes in the boundary layer, which have not yet been modelled, play a very important role in mercury evasion, or that there are large amounts of mercury in the Mediterranean\ud that have so far not been discovered

Simulation of mercury evasion between air and water with 3-D model PCFLOW3D in the Gulf of Trieste

This diploma paper focuses on evasion of mercury in the Gulf of Trieste and its calculation which is made in two ways. Preliminary simulation was performed by the use of the Excel tool with measured mercury concentrations in the water and air of the Gulf of Trieste area. Modelling simulations were performed by a three-dimensional baroclinic mathematical model PCFLOW3D. Both calculations are based on Wanninkhof's gas exchange model (GEM). The PCFLOW3D model consists of modules which can calculate hydrodynamics, transport and dispersion of suspended sediment including resuspension and transport as well as the dispersion of mercury in its dissolved and particulate forms. In the biogeochemical module we can simulate some transformation processes. The exchange with the bottom sediment and the atmosphere, methylation, demethylation, reduction and oxidation can be taken into account. The data about temperature and salinity conditions, wind, deposition and mercury concentrations in the Gulf of Trieste as well as in the Soča River discharges, temperatures and concentrations of different mercury species were collected and interpreted. On the basis of the seasonally averaged parameters and values in a few shorter sequences, a scenario of one-year simulations was established. The agreement within a factor of two was achieved between the results of the model and the preliminary simulations. Both sets of results helped to improve the annual mercury mass balance of the Gulf of Trieste

Application of numerical models of oil spills in the sea

Uporaba numeričnih modelov ob razlitjih nafte na morj