In studies on chemical contamination of soils, little attention is paid to disguised solonchaks. This is due to the low significance of disguised solonchaks for agriculture and the lack of significant pockets of chemical contamination in the areas of their extension. At the same time, these soils are widely extended in the coastal landscapes and perform important ecological functions. They are involved in the maintenance of biodiversity and the sustainable functioning of natural ecosystems. As shown by the current study, the contamination by Cr, Ni, Cu, Pb and oil leads to a deterioration of the biological properties of the hydromorphic estuary carbonate solonchak. This means decrease in the total number of bacteria, the activity of catalase and dehydrogenase, cellulolytic ability, abundance of the Azotobacter genus bacteria, as well as worsening indicators of radish seeds germination and initial growth. In terms of toxicity to the biological properties of the investigated marsh solonchak the studied elements form the following sequence: Cr>Cu>Ni>Pb. High toxicity of Cr compared to Pb, Ni and Cu in marsh solonchak is explained by weak alkaline reaction, in which CrO 3 is transformed into highly toxic chromate.