SIMPLIFIED REPRESENTATION OF THE BIOFOULING FOR TRANSPORT MODELING OF GEOSYNTHETIC FRAGMENTS IN THE CONDITIONS OF THE BALTIC SEA

Fragments of a gabion mesh coating are one of the types of plastic pollution in the World Ocean. Gabions located onshore are subjected to destructive wave action, and plastic coating fragments with positive buoyancy are carried by currents over considerable distances. The trajectories of fragments in the sea depend on their hydrodynamic properties. Entering the marine environment, any solid body undergoes biofouling. It means that a layer of micro- and then macro-algae appears on the surface of the substrate. Naturally, the appearance of a biofilm leads to a change of the hydro-physical properties. The paper proposes a method for calculating the volume of biomaterial on a coating fragment depending on the time spent in the marine environment. It is assumed that the concentration of microalgae in water is constant, and each microalgae particle has a known volume. The number of microalgae on a fragment of the coating can increase both due to the difference in the speeds of movement of microalgae and the fragment, and due to the primitive exponential growth in the number of microorganisms in the colony. The system of equations for finding the volume of biomaterial on a model object – a cylinder of finite length is resolved. Based on the known volume of biomaterial, we can calculate dependencies of the thickness of the biofilm and the effective diameter of the object “coating fragment + biofilm” against the time spent in the marine environment. The modeling results are compared with experimental data on biofouling in the coastal zone of the Gulf of Gdansk of the Baltic Sea. The obtained dependences of the effective diameter on time are supposed to be used for subsequent modeling of the movement trajectories of the gabion mesh fragments in the Baltic Sea.

plastic, biofouling, buoyancy, Baltic Sea