Industrial development of coastal cities and ports renders significant influence on the geological and environmental conditions in the offshore zones and results in formation of complex manmade sediments, which are usually characterized by anomalously high contents of toxic and heavy metals, petroleum products and other compounds having adverse impact on vegetation, animals and humans. The paper presents a comparative characteristic of heavy metal content (copper, zinc, nickel, lead, etc.) in bottom sediments in the northern part of the Gulf of Finland in order to assess the degrees of pollutant concentration and occurrence forms as well as conditions of their migration.