Contamination of Norway Spruce (Picea abies (L.) H. Karst.) Needles with Heavy Metals under Conditions of Technogenic Emissions

The elemental composition of Norway spruce needles in spruce forests with varying degrees of heavy metal contamination in the North-West of Russia has been considered. The aim of the research has been to evaluate the content of Cu, Zn, Mn, Fe, Ni, Pb, Cd and Cr and their pair correlations in the needles of Norway spruce trees in stands located at a distance of 5–31 km from metallurgical enterprises and thermal power plants and near roads with different traffic intensity. Sample collection and determination of the amount of elements in the needles have been carried out using standard techniques. Data analysis has been performed using the Python 3.8 programming language. The comparison has been performed using nonparametric methods. The contamination of the sample plots has been characterized using the coefficients of concentration, the same as Contamination Factor (CF), of elements in the needles and the total indicator of contamination. The average level of pollution has been detected at sites 5 and 12 km from the metallurgical enterprise in the city of Gatchina, the Leningrad Region, and 25 km from the Cherepovets State District Electric Power Station (50 km from the city of Cherepovets), the Vologda Region. Low levels of pollution have been noted near highways in the Luybansky Forestry of the Leningrad Region, 5 and 12 km from the Cherepovets State District Electric Power Station. The elemental composition of the needles at all sites has been characterized by a slightly lower content of Cu, Ni, Mn, and Zn and a significantly higher amount of Pb, Cd, and Cr than in the background stands of Northern Europe. In the area closest to the city of Gatchina, a Mn deficiency has been detected in fir trees of the 1st layer and undergrowth. Reliable Spearman correlation coefficients have been found for the median content of Cu and Cr (r = 0.89, the Gatchina Forestry), Pb and Cd (r = 0.83, the Kaduy Forestry), Ni and Cd, as well as Ni and Pb (r = 0.89 and r = –0.88 near highways in the Lyubansky Forestry) in the needles. The results of the research can be used to improve the methodology for environmental monitoring of territories using spruce as a bioindicator.