Assessment of Soil Heavy Metal Pollution by Land Use Zones in Small Towns of the Industrialized Arctic Region, Russia

The European part of the Arctic zone of Russia is one of the most industrially developed regions with a high level of urbanization and many mining enterprises. Soil pollution of different land use zones (parks, urban forests, traffic zones) in three small towns of Murmansk region of Russia (Monchegorsk, Apatity, Kirovsk, population 26–55 thousand people) was studied. Agricultural and background zones near Apatity were also investigated. The total content of heavy metals (HM) (Ni, Cu, Co, Pb, Zn, Mn), the content of acid-soluble (0.2 N HCl extracted), and water-soluble metal fractions (deionized water), hot-water extracted organic matter, and organic carbon were analyzed. Murmansk region has an increased regional background for heavy metals due to the functioning of non-ferrous enterprises. HM content in agricultural soils corresponded to the regional background. The total pollution index (Zc) had the maximal values for Monchegorsk (17–37), which is situated near the Cu/Ni smelter. In Apatity, only soils of the dividing lane had a similar pollution level (17–26), but it was likely related to the not local origin of sand. Soils of different land-use categories in Apatity and Kirovsk have a high share of acid-soluble metals fraction in their total content: Pb (up to 54%) and Zn (up to 47%); in Monchegorsk - Ni (up to 48%), Pb (up to 67%), Zn (up to 80%) and especially Cu (up to 99%), which indicates the anthropogenic origin of these elements. About 1% of the water-soluble fraction of heavy metals in the studied soils was found. Organic matter played a significant role as a geochemical barrier for metal fixing in urban soils. At the same time, the deposition of metals did not have a significant effect on the content of hot-water extracted organic matter as an indicator of the microbial community state. The lowest content of readily available carbon and nitrogen was observed in the areas with young vegetation cover. The preservation of natural green areas and the maintenance of high-quality vegetation cover and urban soils are necessary actions not only for the aesthetic appeal of cities in the Far North, but also to reduce an anthropogenic load on urban ecosystems.