Mercury Pollution of Lake Imandra Sediments, the Murmansk Region, Russia

Abstract

Research on the chemical composition of Lake Imandra sediments (including mercury) was carried out. Lake Imandra is known to be the largest one in the Murmansk region, North-West of Russia. It is the subject of intense pollution by the industrial enterprises and municipal wastewater. It was established that chalcophilic Hg metal, being a high-toxic and dangerous one for the lake ecosystem, entered the lake due to activities of apatite–nepheline and copper–nickel industries. In the vertical Hg distribution, within sediments of the stations which were close to the drainage of apatite–nepheline deposit development, subsurface maximum of sediment cores from 0.6 up to 2.3 μg/g at the depths from 7 up to 14 cm was marked. That was ten times higher than the average background content (0.044 μg/g). These values were higher up to an order of magnitude than the Interim freshwater sediment quality guidelines (ISQG) and 5 times higher than the Probable effect level (PEL) for Hg according to Canadian Sediment Quality Guidelines for the Protection of Aquatic Life (2018) ( http://st-ts.ccme.ca/en/index.html ). The Bolshaya Imandra should be classified as “Class III” with the marked contamination according to the Environmental Classification System of the Norwegian Pollution Control Authority (Classification of environmental quality in fjords and coastal waters. A guide. Norwegian Pollution Control Authority, 1997). Hg content was in a wide range from 0.02 up to 1.0 μg/g in the surface of 1-cm sediment layer. The maximum Hg concentrations were confined to the water areas of the effluents from apatite–nepheline and copper–nickel industries.