A mathematical three-dimensional model was developed by combining a physically complete block of circulation with modules of transport and transformation of detritus and polychlorinated biphenyls (PCBs). This z-coordinate model has a horizontal resolution of 5 × 5 km, 45 vertical levels, and a step of 5 minutes. The model considers gravitational sedimentation and decomposition of detritus, as well as its deposition and erosion on the bottom. To calculate the transport and transformation of PCBs in the Sea, the model uses three state variables: the concentration of PCBs in solution, in detritus, and in the upper layer of sediment. It also considers sorption, desorption, and reversible flows of PCBs at the bottom. A 20-day model calculation was performed to simulate a potential accidental release of PCBs in the area of the Danube Delta in spring. The PCBs advection flows dominated and were comparable to the adsorption/desorption flows, while the diffusion fluxes were infinitesimal. Up to 20% of discharged PCBs were adsorbed by detritus in the first two days after the accident. There was a gradual accumulation of PCBs on the bottom; 16 days after the accident, 18% of the PCBs were bound to the sediments. The PCBs transport on detritus serves as a natural buffer mechanism that weakens the spread of PCBs in the sea. The paper analyzes the dynamics of PCB fields formed as a result of the application of an artificial active sorbent to minimize adverse effects on the ecosystem. An end-user oriented software application was developed; it allows forecasting the dynamics of potential releases of PCBs and planning counter-measures. A user-friendly interface allows tracking the field, visualizing the distribution of PCBs in the water column and sediments, and displaying the balance between dissolved and suspended phases. Key words: multidisciplinary model, PCB transport, adsorption, desorption, sediments