Sandimirov S.S. Catalogue of lakes in the Russian, Finnish and Norwegian Border Area. Finland, Jyvaskyla: Kopijyva Oy, 2008.

to approximately one third of the maximum levels in the late 1970s, the deposition of pollutants still has an influence on the quality of the water bodies in the lake. The aver­ age concentrations of Cu and Ni are 1.7 pg/l and 3.7 pg/l, respectively. 2.9.2. Lake bottom sediments The sediments in Lake Langvatn have organic matter contents (LOI) in the upper­ most 1 cm layer ofabout 25% (Table 33). Airborne pollutants from the smelter have a relatively insignificant effect on pollution in the lake. Pollution by chalcophile elements is also relatively minor. Surprisingly, the maximum concentrations of practically all the heavy metals (Cu, Ni, Zn, Co and Cd) occur in the 3-4 cm sediment layer (Fig. 47). The accumulation ofmetals in this layer is presumably due to strong pollution from an unknown source. The contamination factor values for these heavy metals range from 0.4 to 2.6 (Table 33), i.e. the values correspond to low and moderate contamination. Cobolt has the highest Cfvalue. The degree of contamination value (10.7) for this lake orresponds to moderate contamination. Lake Layer, cm LOI Cu Ni Zn Co Cd Pb As Hg cd Langvatn 0-1 25.24 121 52 110 62 0.19 26 4.14 0.096 13-14 20.61 137 31 109 24 0.50 20 3.53 0.056 c, 0.9 1.7 1.0 2.6 0.4 1.3 1.2 1.7 10.7 Table 33. The organic matter con­ tents (LOI, %) and heavy metal concentrations (цд/д, dry weight) in the surface (0-1 cm) and pre-industrial (13-14 cm) sediment layers. Cfand Cdare the contamina­ tion factor and degree of contamination values, respectively. Fig. 47. Vertical distribution of the concentrations ofCu, Ni, Zn and Со (цд/д, dry weight) in the sediment core ofLake Langvatn. 2.9.3. Hydrobiology investigations No direct hydrobiological investigations have been carried out in this lake. ) ил О 100 Mg/g U " В о £ 5 : о<L>тз J.o: ТЗ <L> 15 ^ Catalogue o f Lakes in the Russian, Finnish and Norwegian BorderArea 95