Heavy metals and radionuclides distribution and environmental risk assessment in soils of the Severodvinsk industrial district, NW Russia

The article is devoted to the study of the content of heavy metals and radionuclides in soils of the environments of the Severodvinsk industrial district (Northwest Russia). The city of Severodvinsk is the largest industrial center for the Navy in North-western Russia. Soil samples were taken in the vicinity of the Severodvinsk industrial region in the areas where there are summer cottages and gathering places for wild berries and mushrooms collected by local residents. Heavy metal content studies were performed by ICP-MS. Measurements of the activity of radionuclides were carried out via the low-background semiconductor gamma-ray spectrometry method with a detector of especially pure germanium. Assessment of the degree of soil pollution with heavy metals was performed using geo-accumulation index parameters (Igeo), contamination factor (Cf), degree of contamination (Cd), enrichment factor (EF), and ecological risk index (ERI). The radiation safety parameters of the Severodvinsk industrial region soils were calculated, as were the absorbed dose rate of gamma radiation D_R, the equivalent of radium Raeq, and the external hazard index Hex. The sources of soil pollution are natural (geogenic) and anthropogenic (enterprises of the military-industrial complex, city heating systems, transport). The studies found a low level of heavy metal pollution and radionuclides in the soils of the environments of the Severodvinsk industrial region. Soils can be used by local people to grow food at their summer cottages. Also, the studied area is favorable for the collection of wild mushrooms and berries. However, closer attention should be paid to certain parts of the territory, since for some metals (As, Mn, Cd, and Pb) an increase in the parameters of the degree of soil pollution (Igeo, C_f, C_d, EF, and ERI) is observed.