Distribution of background contents of elements in sediments of Lake Imandra

Abstract

The background contents of the elements in the sediments of the largest lake of the Murmansk region – Imandra – have been investigated. The background concentrations values of the elements have been determined in the deepest parts of the collected sediment cores. The sedimentation rate in the lakes of North Fennoscandia, including the Murmansk region, is on average 1 mm per year, and the range is between 0.3 and 3 mm/year. The collection of sediment cores 20–25 cm long has been carried out during the study of Lake Imandra. Industrial development of unique deposits of sulfide and apatite-nepheline ores on the watershed of Lake Imandra started in the early 30s of the last century. Consequently, the natural background element contents are fixed in the lower layers of the collected sediment cores. Two groups of elements have been identified by the mathematical statistics methods (correlation and factor analysis): the first group is heavy metals, the second group is alkaline (Na and K) and alkaline-earth metals (Ca, Mg and Sr), Al and P. These elements are in elevated contents in the rock-forming minerals on the catchment area of Lake Imandra: the first group is in the northern part of the catchment area (sulfide copper-nickel ores of Monche Tundra), the second group is in the southeastern part of the catchment area (apatite-nepheline deposits of the Khibiny Alkaline Massif). The largest average background contents of heavy metals (except Co, Pb and As) are noted in the northern part of the Bolshaya Imandra; Ca, Na, Sr, Al and P – in the southern part of the Bolshaya Imandra; Mn – in the Yokostrovskaya Imandra, and Fe – in the Babinskaya Imandra, which is associated with specific conditions for the formation of oxides and hydroxides of these metals in the sediments. The highest background contents of K and Mg are noted in the Babinskaya Imandra, which may be due to the wide distribution of clay minerals with a high content of these metals.

Keywords

• heavy metals
• sediments
• Lake Imandra