Metals with a density of more than 5 g/cm3 are classified as heavy metals. Heavy metals occur naturally in bedrock, soil, plants and animals in the form of minerals, water-soluble ions, salts or gases.
These metals can also be incorporated into organic or inorganic molecules, or bound to particulates transported in the atmosphere. Heavy metals are never lost from the element fluxes in nature but can change the chemical form in which they occur.
The most problematic heavy metals from the point of view of the environment are mercury (Hg), lead (Pb) and cadmium (Cd). In addition to being toxic to living organisms, many heavy metals, such as copper (Cu), zinc (Zn) and iron (Fe), are also essential micronutrients for the metabolism of plants and animals. Some metals can occur in forms that are especially toxic, even in relatively small amounts, and pose a threat to the health of man and animals.
Heavy metals are emitted into the atmosphere or released into the watercourses from three main sources: the combustion of fossil fuels, non-ferrous smelting industries and the burning of waste. However, heavy metals are also released into the atmosphere and watercourses as a result of natural processes, such as volcanic eruptions.
The Inari-River Pasvik area is mainly affected by heavy metal emissions from the Pechenganikel mining and smelter plants at Nikel and Zapoljarny. The metals released into the environment from the production processes are primarily Ni and Cu, as well as to a lesser extent cobolt (Co) and arsenic (As). Heavy metals are deposited in the lakes and streams, on the ground and trees and other vegetation in the immediate vicinity of the production units. Metals are also transported via the atmosphere into areas far from the emission sources. Due to the prevailing wind direction, the area to the north of the complex receives the greatest deposition load.
The soil in the immediate vicinity of the smelter is seriously contaminated by heavy metals. Because the metals are strongly bound to organic matter in the soil the accumulation of metals in the soil has continued throughout the lifetime of the industrial complex. The seriousness of the problem lies in the fact that, even though the emissions of metal pollutants would decrease or cease completely, the heavy metals will remain in the soil and continue to be cycled within the ecosystems for decades or even centuries to come. Heavy metals have accumulated in the vegetation, bottom sediments of the watercourses and uppermost layers of the soil for over 70 years already.
The deposition load is at its greatest close to the smelter. The impact of emissions on terrestrial ecosystems is extremely severe in the immediate vicinity of the complex and gradually decreases with increasing distance from the emission sources. The effects of emissions are clearly evident in the elevated Ni and Cu concentrations in, for example, the leaves of bilberry and birch and needles of Scots pine. This is even more pronounced in the heavy metal concentrations in mosses and lichens. The load on the environment is at its greatest in the spring and during the summer.
Nickel and copper deposition is harmful to the environment because metal accumulates in living organisms. The mosses and lichens growing on the ground and on tree trunks primarily receive their mineral nutrients (including metals) from rainfall and snowmelt and as a result heavy metals accumulate strongly in their tissues. The metals in the vegetation pass into herbivores and subsequently into predators, with the end result that the whole food chain gradually becomes poisoned. High heavy metal concentrations have been recorded, for instance, in fish and birds.
