Sandimirov S.S. Chemical Composition of Bottom Sedimentary Deposits in Lakes in the Zone Impacted by Atmospheric Emissions from Severonickel Plant. Geochemistry International. 2010, Vol. 48, №11, p. 1148-1153.

1152 DAUVALTER et al. Pagel’ Lake and 19.8% of the area of Mocheozero Lake. The ore occurs mostly in brown oozes, although it was also found in the green oozes. The conditions under which Fe—Mn nodules were formed in lakes in Murmansk oblast and in northern Sweden and Fin­ land were described in [15]. Knowing the evolutionary history of the predomi­ nant pollution source, one can evaluate the sedimen­ tation rate. SNP was commissioned in 1938 to process veined Cu—Ni ores from the Nitis—Kumuzh’e deposit. In 1946—1947, the plant also processed ores from the Pechenga district with approximately 6.5% S, i.e., the own reserves of Cu—Ni ores had been depleted. After the expansion and restructurization of the plant, its production was increased by a factor of 2.7 in 1960. Before 1967, atmospheric emissions from the plant did not undergo preliminary purification. In 1967, the utilization of sulfur in metallurgical gases was begun at the plant to produce sulfuric acid. The amount of ores provided by the Pechenganickel min­ ing and metallurgical integrated works is inadequately small for the capacity of the Severonickel plant, and hence, the plant started to process Cu—Ni ores from Norilsk (with 30% S) in 1969. In 1970—1976, the pro­ cessing of S-rich ores was increased by almost one order of magnitude. The emissions were drastically increased after 1972 because of the increase in the amount of ores from Norilsk to be processed. The greatest sedimentation rate and the highest concentrations of heavy metals in the upper layers of BD were determined in Malevoe Lake. The first increase in the Ni, Cu, and Co concentrations (the principal contaminants in the area) was detected in the layer 12—13 cm. With regard for the thickness of the layer of accumulated contaminated BD (the middle of the layer 125 mm) and the duration of the activity of SNP by the time when the BD were sampled (66 years), it can be readily calculated that the average sedimentation rate at this time was 1.9 mm/year. A decrease in the contents of principal contaminating heavy metals (Ni, Cu, and Co) in the layer 6—7 cm can be explained by the beginning of sulfur utilization and the separation of the aforementioned metals in 1967. Starting at that time, the sedimentation rate in Malevoe Lake was 1.8 mm/year (on average), which is consistent with earlier estimates. The analogous two events in Mocheozero Lake left records at depths of 6.5 and 2.5 cm, respectively. The average sedimenta­ tion rate in Mocheozero Lake was estimated at approximately 1 mm/year over the past seven years and at 0.7 mm/year for the past four decades. The concentrations of major contaminating heavy metals in Pagel’ Lake are at a maximum in the layer 2—3 cm and are explained by the beginning of production at SNP. Because of this, the sedimentation rate in this lake can be evaluated at 0.4 mm/year on average. Among the lakes examined in the course of this research, Malevoe Lake is the smallest and the shal­ lowest, has the smallest drainage area and, corre­ spondingly, the highest specific amount of supplied allochthonous mineral and organic material that forms BD. Because of this, the sedimentation rate in Malevoe Lake is the highest. Mocheozero Lake is the largest and deepest among the lakes in question, its drainage area is 1583.5 km2, and the area of the lake itself is 38.6 km2. Mocheozero Lake links the lacus­ trine-riverine systems of the Monche and Volchie tundras and controls their base level of erosion. Hence, the sedimentation rate in this lake is two times lower than in Malevoe Lake. CONCLUSIONS Data on the chemical composition of BD indicate that the lakes in question were significantly impacted by anthropogenic processes, first of all, atmospheric emissions from SNP. This resulted in an increase in the Ni, Cu, Co, Hg, Cd, Pb, and As concentrations in the surface layers of the BD. Ecologists class the latter four elements with globally contaminating elements, par­ ticularly in the Arctic and subArctic zones of the northern hemisphere [16]. The contamination coeffi­ cients of these elements are as high as 43.3 (Pagel’ Lake), 10.7 (Pagel’ Lake), 10.7 (Pagel’ Lake), and 35.6 Malevoe Lake), respectively. These elements are extremely toxic for aquatic organisms, and hence, the strong contamination of the BD and surface waters with these elements is highly hazardous for all ecosys­ tems and the human population of the Monchegorsk area. The greatest degrees of contamination, calculated as the sum of the contamination coefficients of eight elements (Ni, Cu, Zn, Co, Cd, Pb, Hg, and As) were detected in Malevoe Lake (table). This lake is closer to SNP than the other lakes and, hence, is affected by a stronger anthropogenic load. The second most con­ taminated water body is Pagel’ Lake, which is located farther away from the plant and away from the pre­ dominant airflow direction. The bulk of the drainage area of Mocheozero Lake is situated at a significant distance from SNP, and hence, this lake is much less significantly polluted, although its pollution is also high [8]. The surface layers of BD in Mocheozero Lake are significantly enriched in Mn and Fe, but this is explained not by anthropogenic contamination but by the geochemical conditions in the bottom waters and the surface layers of the BD. Elevated iron and manga­ nese concentrations in the surface layers of BD can be explained by high concentrations in the bottom waters and the upper part of the BD and by the oxygen deficit in the underlying BD layers, in which iron and manga­ nese are transferred into soluble lower-oxide modes and migrate to the surface layers of the BD. These GEOCHEMISTRY INTERNATIONAL Vol. 48 No. 11 2010