BACKGROUND CONCENTRATIONS OF HEAVY METALS AND OTHER CHEMICAL ELEMENTS IN THE SEDIMENTS OF SMALL LAKES IN THE SOUTH OF KARELIA, RUSSIA

Abstract

The average background concentrations of 42 elements, including heavy metals which are the most dangerous pollutants of the environment, were calculated based on detailed research of sediments of 15 small lakes in the south of the Republic of Karelia. The sediment samples from the lakes were collected from 2016 to 2018. The main items of equipment were a gravity sampler Limnos and hand sampler. The former is capable of producing a 60 cm core and dividing it into 1 cm layers, the latter can enter sediment to a depth of 15 m. All samples were prepared by chemical analysis and measured using uniform methods. The concentrations of chemical elements were taken by the mass-spectral method on a ХSeries-2 ICP-MS. To reveal the layers accumulated in the pre-industrial period, similar research of the area of the Murmansk region and countries of the Scandinavian Peninsula were used. Besides this, the geochemistry and geochronology of lake studies of the author were also used. Eventually, from 73 to 76 samples were taken for an assessment of background concentrations of heavy metals and other elements in the sediments of the lakes from Karelia's south. Given that the data obtained do not obey the normal distribution law, which is often found in geochemistry, the median sample was taken as the averaged background concentration of chemical elements. The results were similar to analog data for neighboring regions, including the Murmansk region and Scandinavian countries. Moreover, the levels of accumulation of chemical elements in lake sediments of Karelia's south are similar to some of the data for stream sediments of the studied region. The exceptions were elements controlled by terrigenous fractions of the stream sediments. This fraction is more rapidly accumulated in the stream and river sediments than in lake sediments. New data can be used for future environmental and geochemistry studies of the sediments of small lakes subject to anthropogenic impact.