The study examines the consequences of a forest fire in a radioactively polluted area in the Chernobyl accident zone, namely the transfer of radioactive substances and their impact on the environment and radiation situation. The purpose of the study is to develop a mathematical model of the transfer of radioactive substances and a methodology for integrated assessment of the ability of an ecosystem to retain deposited radionuclides. The research methodology is based on existing proven mathematical methods and models, such as the turbulent diffusion model, the Gaussian static model, and the hierarchy analysis method (Thomas L. Saaty method). Models were obtained for the formation of a radioactive smoke cloud and its migration in the atmospheric air, the spread of radioactive aerosols and gas components, taking into account convection, turbulent exchange, humidity, wind strength and direction over the combustion zone. The processes of blowing and fluttering in the wind by the wind as the horizontal migration' perturbers of radioisotopes represent a new, still insufficiently studied area of research. Integral indicators for assessing the ability of the forest natural complex' components to reliably accumulate and retain radioisotopes that have settled have been determined. It was revealed that the priority factors of impact on the environment and the degree of radioactive contamination are the activity and directions of migration of combustion products, which constitute radioactive contamination.