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

FINNISH LAKES 3.1. LAKE AITTOJARVI Lake Aittojarvi (watershed of the River Paz) is located 50 km to the west of the town ofNickel and 69.2 km to the north of the settlement of Nellim in Finland. It is a small (area of the lake 57.3 ha), shallow-water (maximum depth 5 m) lake with an elongated oval shape and indented coastline, and is of glacial ori­ gin. The maximum length is 1.5 km and maximum width 0.77 km. The point of maximum depth is located in the central part of the lake. The watershed area belongs to the forest zone. The lake shores are high and covered by shrubs and pine forests. Physico-geographical characteristics Watershed River Paz Latitude 69°25.575' Longitude 28°57.482' Height above sea level, m 164.0 Maximum length, km 1.50 Maximum width, km 0.77 Maximum depth, m 5.0 Area, hectares 57.252 Watershed area, km 2 8.018 Study period 2005-2006 3.1.1. Hydrochemistry The water of the lake is slightly acid and has a low mean total mineraliza­ tion (12.7 mg/l) and mean alkalinity of 77 peq/1. During flood periods the pH ofwater drops, but acidification does not develop due to the buffering capacity of the water. The lake has low concentra­ tions ofbase cations and anions, with so­ dium (average 1.7 mg/l) and bicarbonate (average 4.7 mg/l) predominating. Total P and N concentrations in water are the main criteria used for as­ sessing the development of water eu- trophication. The concentrations and relationships between the species of P and N 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 and total N during the vegetation period are up to 6 pg/l and 230 pg/l, respectively. According to the concentrations of mineral nutrients, the lake is classified as oli- gotrophic. The lake also has colour values and organic matter (up to 3.5 mg/l) and Fe concentrations (mean 173 pg/l) typical of small water bodies in the region. During high water periods in the summer, the concentrations of P 0 43’ and N 0 3",which deter­ mine the lake productivity, are low. Hydrochemical properties pH 6.48 6.06-6.77 Electrical conductivity, mS/cm 21 15-29 Ca, mg/l 1A 1.0-2.3 Mg, mg/l 05 0.4-0.7 Na, mg/l 1 1 1 .4-2.2 K, mg/l 03 0.2-0.4 HC03, mg/l 47 3.1-9.6 S04, mg/l 2Л 1 .6-3.0 Cl, mg/l 19 0 . 8 - 2.8 Total mineralization, mg/l 12.7 9.8-18.9 Alkalinity, (jeq/l 71 51-157 Alhough the watershed of Lake Aittojarvi is relatively remote from the Pechen­ ganickel smelter (50 km), it is subjected to the impacts of anthropogenic pollution. The Catalogue o f Lakes in the Russian, Finnish and Norwegian BorderArea