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

Total P and N concentrations in water are the main criteria used in assessing the development ofwater eutrophication. The concentrations and relationships between P and N species vary according to the season, and the dynamics is to a greater extent de­ termined by the level of production and, consequently, the trophicity of the water body. The concentrations of total P (up to 14 [ig/1) and total N (up to 276 fig/1) changed slightly during the study period. According to the concentrations of mineral nutrients, the lake is classified as tran­ sitional to eutrophic. The lake also has higher colour values, organic matter concentra­ tions (8.4 mg/l) and Fe concentrations (mean 125 [ig/1) compared to other lakes in this region. The water exchange index is 0.6, i.e. full water exchange in the lake takes about 6 months. The bottom of the lake is covered with a thick layer of silt, which consists of undecomposed zooplankton debris and organic matter. During high water periods and high precipitation in the autumn, the concentrations of min­ eral nutrients (P 0 43' and N 0 3") that de­ termine the lake productivity are low. The watershed area of the lake is subjected to anthropogenic impacts from the smelter. The main pollutants are sulphur compounds and heavy metals (Ni, Cu etc.). Maxi­ mum Ni concentrations (9 [ig/1) oc­ curred in the water during the 1990s. At the present time, due to the reductions in emissions, there are higher Cu con­ centrations (up to 3.8 [ig/1) during the summer mean water period, and of Ni (up to 4.4 [ig/1) during periods of high water. 1.3.2. Lake bottom sediments The sediments of Lake Keudsherjaur are characterized by relatively high organic mat­ ter contents: the LOI value in the uppermost 1 cm layer is slightly below 30% (Table 3).The lake is located at a distance of 28 km from the smelter complex, and is exposed to the deposition of heavy metals (Ni, Cu, Co) and chalcophile elements (Pb, As, Cd and Hg).The top 3-4 cm of the lake sediments is the most heavily polluted by Ni, Cu and Co. Pollution by chalcophile elements started earlier: the top 5-7 cm of the sedi­ ments especially is polluted by these elements (Fig. 3).The contamination factor values of these toxic elements range from 2.2 to 9.4 (Table 3), i.e. the values correspond to considerable and high pollution contamination. Pb has the highest Cf value. The de­ gree of contamination value (41.5) for this lake corresponds to high contamination. Cu, (jg /i 2.7 1.9-3.8 Ni, цд/І 4.6 3.1-9.0 Al, цд/І 40 16-93 Pb, цд/І 0.3 0.2-0.5 Water colour, deg. 30 22-39 NH4, |ig/l 19 7-28 no 3, ng/i 3 1-8 Total N, (jg/l 226 202-276 P04, ng/l 1 1-1 Total P, |jg/l 9 1-14 Catalogue o f Lakes in the Russian, Finnish and Norwegian BorderArea