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

vegetation period. In 1991, however, the maximum total N concentration was 583 pg/l; such a high concentration has subsequently not been recorded. Based on the concentrations of mineral nutrients, the lake is classified as oligo- trophic. The lake also has colour values, and organic matter (up to 5.6 mg/l) and Fe concentrations (mean 54 pg/l) typical of small water bodies in the region. The trophic type of the water body is to a considerable degree determined by the location of the River Madsash in the hydrographic system. The water exchange index is 0.96, i.e. full water exchange in the lake takes about 1 year. Due to specific morphometric features, which determine the inflow and outflow in the southern part of the lake, the natural water exchange of the lake is actually slow. Because suspended particles are deposited more effectively, the bottom of the whole lake is covered with a thick layer of silt. The silt consists of undecomposed zooplankton debris and organic matter, which is of primary importance for the nutrition of whitefish species. The conditions for the growth of food organisms are obvi­ ously highly favourable. Because most of the lake is not deep, the circulation of mineral nutrients in the water is faster in the summer; this also increases the production capacity of the water body. During periods of high water and high precipitation episodes in the autumn, the concentrations of species of mineral nu­ trients (P 0 43_and N 0 3) that determine the lake productivity are low. The low concentrations of micronu­ trients in the water indicate a low input to the water body from the chemical weathering of mineral material in the watershed. As noted above, peak emis­ sions from the Pechenganikel smelter during the late 1980s and early 1990s re­ sulted in high concentrations of Cu (18 pg/l) and Ni (3 pg/l) in the water. At the present time, airborne pollutant deposition results in a higher content of Cu (up to 3.4 pg/l) and Ni (up to 3.6 pg/l) during snowmelt. 1.16.2. Lake bottom sediments The sediments of Lake Kochejaur have very high organic matter contents: the LOI value in the uppermost 1 cm layer is more than 50% (Table 16).This is due to the fact that the lake is relatively shallow and highly productive. The lake is located at a distance of 110 km from the Pechenganikel smelter. As a result, the lake is mainly subjected to pollution by chalciphile elements, such as Pb and Cd. The uppermost 5 cm of the lake sediments is the most heavily polluted (Fig. 13). The contamination factor values of these two elements are 14.1 and 3.9, respectively (Table 16), i.e. the values correspond to high and considerable contamination. The contamination factor values for other heavy metals correspond to moderate contamination. The degree of contamination value (26.3) for this lake corresponds to considerable contamination. Water colour, deg. 20 11-32 NH4, мд/І z 1-23 N03, цд/І 4 1-38 Total N, цд/І 224 139-583 po 4 цд/і 1 1-3 Total P, цд/І 5 1-14 Fe, цд/І 54 14-159 Cu, (jg/l 1.70 0.20-18.0 Ni, цд/І 09 0.1-3.0 Al, цд/І 31 5-46 Pb, цд/І 03 0 . 1 - 0.8 Catalogue o f Lakes in the Russian, Finnish and Norwegian BorderArea