Analyzing the status of northern taiga forests amid reduced Severonikel emissions

Abstract

Based on the analysis of rain- and snowfall, as well as soil waters and conifers (1991–2014), this paper evaluates the status of the forest ecosystems in the Murmansk Region since the copper-nickel plant Severonikel owned by Kola MMC started to cut its emissions. The analysis focused on low-shrub spruce forests with green mosses and low-shrub lichen pine forests going through different stages of degradation caused by human activity. Coniferous forests situated in the impact area have high background concentrations of the main pollutants — i.e. heavy metals and compounds of sulphur, present in different components of the forest ecosystems. The closer it is to the source of emissions, the higher the concentration of pollutants is in rain- and snowfall, as well as in soil waters and conifer tree needles in both pine and spruce forests. The paper demonstrates inter- and intrabiogeocenotical variability in the composition of rain- and snowfall and soil waters in northern taiga forests. The concentration of nickel and copper is typically higher under the trees than in between them, and in spruce forests as compared with pine forests. A significant variability in the chemical composition of rain- and snowfall and soil waters was established. Observations showed a reduced amount of the major pollutants penetrating the soil waters and then falling out with rain in the impact areas with light forest, which is indicative of the airborne industrial pollution levels gradually going down. High concentrations of S, Ni, Cu in the conifer tree needles were noted in 1991, i.e. in the period of major air pollution. The authors looked at the concentrations of heavy metals over the period of over two decades in which emissions were being cut down. Their analysis showed that the concentration of nickel and copper in the pine tree needles of different ages went down in defoliating forests and impact areas with light forest, as well as in the spruce tree needles in the area around the pollution source, in the impact areas with light forest. It is shown that the concentration of sulphur in the pine tree needles went down compared with the 1991 data and reached the level of background variation in defoliating forests and impact areas with light forest. The spruce tree needles saw lowered concentrations of sulphur in the impact areas with light forest in 2007 and 2012.This research study was funded under a governmental assignment (State Registration No. АААА-А18-118021490070-5), as well as under the following grants by the Russian Foundation for Basic Research: 18-05-60142_Arktika and 18-35-00170 mol_a.