Вестник МГТУ. 2020, Т. 23, № 1.

in the south of Karelia is comparable with similar data for stream sediments, as well as for lake sediments in the neighboring regions of Russia and other countries. Fig. 5. Trends of chondrite normalized ( Белкина и др., 2012) averaged REE levels in the lakes in the south of Karelia compared to the continental crust Рис. 5. Тренды нормализованных по хондриту (Белкина и др., 2012) усредненных содержаний РЗЭ в озерах юга Карелии по сравнению с континентальной корой Fig. 6. Average background levels of chemical elements in lake and stream sediments from Karelia’s south Рис. 6. Средние фоновые уровни химических элементов в озерных и речных отложениях юга Карелии On the other hand, one cannot but take into account the fact that contemporary studies and those conducted earlier employ completely different methods and instruments and may have purely technical inconsistencies that are not related to the natural distribution patterns of chemical elements. Ultimately, the results will be most relevant when studying lake sediments in the northern regions of Russia, geologically close to the southern part of Karelia. In addition, further studies will be conducted to collect more accurate data on the background levels of chemical elements in heterogeneous lake sediments in the Republic of Karelia and, possibly, neighboring regions. Large-scale similar studies in Siberia have shown that organic silts, mineral, ferruginous, and carbonate sediments can have significant differences in terms of geochemistry (Страховенко, 2011). Considering that in Karelia and Murmansk Region, in addition to carbonate sediments, almost all types of recent lake sediment are present, which also include diatomites and diatom sapropels containing a significant share of fossil diatom valves (Синькевич и др., 1995; Демидов и др., 2006), such studies appear to be highly relevant. Moreover, one should take into account the absence in Russia of any standards governing the concentrations of chemical elements, primarily HMs, in the sediments of different water bodies.