Biogeochemical assessment of heavy metal contamination of soil and vegetation cover of the Kanonersky island

The authors have evaluated pollution with heavy metals (Cd, Cu, Ni, Pb and Zn) in the soil and vegetation cover of the Kanonersky Island, St. Petersburg. The reconnaissance survey has identified the Western High Speed Diameter (WHSD) as a significant source of pollution. The territory of the island was divided into 4 zones according to their functional use and wind regime: recreational, transitional, windward and leeward relative to the WHSD. The main soil contaminants are Pb and Zn with concentrations varying from 5 to 376 mg/kg and from 16 to 1131 mg/kg (for mobile forms) and from 46 to 1179 mg/kg and from 64 to 2903 mg/kg (for gross content), respectively. The highest degree of MAC surcharge was found for the mobile forms of metals: Pb (63-fold in the transition zone) and Zn (50-fold on the windward side of the WHSD). The coefficient of total soil pollution with heavy metals ranged from 2 to 104 for the mobile forms and from 5 to 55 for the gross content. Maximum values were recorded in transition and windward zones, therefore soils of these territories were classified as moderately polluted. The highest mobility among the considered heavy metals on the island is for Pb (29 % – average percentage for its mobile forms), while the lowest is for Ni (4 %). At the same time, the accumulation by plants becomes higher in a row Pb < Cd < Ni < Cu < Zn. The highest values for Zn and Cu were recorded in tree leaves on the leeward side of the WHSD. The general assessment of the state of soil and vegetation cover of the Kanonersky Island revealed a moderate degree of soil contamination with the main localization on the windward side of the WHSD and partially in the transition zone.