Catalogue of Lakes in the Russian, Finnish and Norwegian Border Area = [Каталог озер в приграничном районе России, Финляндии и Норвегии] / Nikolay A. Kashulin, Vladimir A. Dauvalter, Sergey S. Sandimirov etc. - Apatity : Institute of the North Industrial Ecology Problems KSC RAS etc., 2008.

drops slightly, i.e. oxidation processes do not develop due to the buffering capacity of the water. The lake is has low concen trations of base cations and anions, with sodium (average 6.49 mg/l) and chloride (average 10.7 mg/l) predominating. The annual chemical cycle of the lake is characterized by an insignificant de crease in total mineralization, oxidizabil ity and pH during flood periods and epi sodes of high precipitation when there is an increase in the inflow of humic water into the lake. Based on the concentrations of min eral nutrients, the lake is classified as oli- gotrophic. The concentration of total P is 5.5 pg/1 and of total N 216 ^ig/1. The lake also has colour values, and organic matter (3.0 mg/l) and Fe concentrations (mean 50 pg/1) typical of small water bodies in the region. During episodes of high precipitation in the summer the concentrations of species of mineral nu trients (P 0 43_and N 0 3~) that determine the lake productivity are low. The water exchange index, which regulates the concentrations of mineral nutrients in the lake, is 0.6, i.e. full wa ter exchange in the lake takes about 6 months. The bottom of the lake is cov ered with a thick layer of silt, which consists of undecomposed zooplankton debris and organic matter. This is of primary importance for the feeding of ichthyofauna. Obviously, Conditions for the growth of food organisms are obvi ously highly favourable. The low concentrations of micronu trients in the water body are related to the low rate of chemical weathering of the mineral material in the watershed. Although the watershed of Lake Njas- jukkajarvi is relatively remote from the Pechenganikel smelter (28 km), it is still subjected to anthropogenic impacts. The main pollutants are sulphur compounds and heavy metals (Ni, Cu, Co, etc.) In spite of the fact that emissions from the smelter have been reduced to approximately one third of the peak levels in the late 1970s, the deposition of pollutants still has an impact on the water body. The average Cu and Ni concentrations are 1.9 pg/1 and 7.6 pg/1, respectively. pH 6.79 6.68-6.88 Electrical conductivity, mS/cm 59 54-65 Ca, mg/l 2.17 1.95-2.48 Mg, mg/l 1.28 1.16-1.45 Na, mg/l 6.49 6.10-7.07 K, mg/l 0.65 0.61-0.71 HC03, mg/l 57 4.8-6.1 S04, mg/l 6 2 4.7-8.2 Cl, mg/l 10.7 9.4-12.6 Total mineralization, mg/l 33.3 29.9-36.4 Alkalinity, neq/l 93 79-100 Water colour, deg. 12 8-23 NH4, цд/І 11 4-23 N03, цд/І 16 3-44 Total N, цд/І 216 77-473 P04, цд/І 2 1-5 Total P, |ag/l 5 3-8 Fe, ng/l 50 10-115 Cu, мд/і 19 1.1-2.6 Ni, цд/І 2A 5.5-9.9 Al, цд/І 48 11-69 Pb, цд/І 0.38 0.21-0.50 Catalogue ofLakes in the Russian, Finnish and Norwegian BorderArea