Sandimirov S. Pollution of the Sediments of the Paz River basin / In State of the environment in the Norwegian, Finnish and Russian border area. The Finnish Environment. Finland, Jyvaskyla: Kopijyva Oy. 2007, №6, 98p.

3. Pollution of the Sediments of the Russian Lakes of the Paz River System During three field expeditions (August 2002, August 2003, August 2004) nineteen Russian Lakes o f the Paz River basin (Kochejaur, Virtuovoshjaur, Alla-Akkajarvi, Kuetsjarvi, Kaskama- jarvi, Porojarvi, Shuonijaur, Keudsheijaur, LN-2, LN-3, LN-4, Palojarvi, Zapoljarny, Trifono- jarvi, Kjantejarvi, Kirikovanjarvi, Njasjukkjajarvi, Pikku-Heynjajarvi, Peschanoe) have been in­ vestigated to study chemical composition o f sediment cores and assess the pollution o f water ecosystems. 3.1. Background Concentrations of Heavy Metals The maximum background concentrations o f heavy metals that were recorded in LN-2 (Ni, Cd, Hg), Porojarvi (Cu, As), Kuetsjarvi (Zn, Pb), Trifonojarvi (Co) Lakes result from the geochemi­ cal and morphometric features o f the lake and its drainage basin. The background concentra­ tions o f the polluted heavy metals and As in the abovementioned lakes were established to be higher than those in other lakes under study by a factor o f 1.5 - 10. Minimum concentrations in the deepest parts o f the sediment cores o f the Russian investigated lakes were noticed in the south-west part o f the studied territory (Kochejavr, Virtuovoschavr, Alla-Akkajarvi), as well as quite close to the industrial centre (Shuonijaur, Keudsherjaur, LN-3). The average background concentrations o f heavy metals and As in sediments o f the investigated Russian lakes o f the Paz River System are approximately equal to earlier calculated average background concentrations in lake sediment o f the Kola Peninsula and the Paz River Basin in 1991 - 1992 (Dauvalter, 1994a, 1994b), excepting Cd (see Table 4). The average background concentration o f Cd was more than 10 year ago in 5 times higher than in our recent investigations. Probably, it has taken place due to more perfect analytical equipment for definition of Cd contents in present time. 3.2. Vertical Distribution of Heavy Metals in Bottom Sediments Markedly elevated concentrations o f Cd, Pb and As were revealed on the sediment surface in the Kochejavr Lake (Fig. 1); at a depth o f 10 cm and lower, their concentrations in the sedi­ ments core are equal to background values. In a large number o f lakes, the influx o f Pb results from its deposition from the atmosphere and from autopollution (vehicles). The accelerated ac­ cumulation o f Pb is, apparently, due to the air pollution by Pb, which is ubiquitous in the north­ ern hemisphere. In the sediment cores o f the Kochejavr Lake there is no the pollution by priority contamination heavy metals for the Kola Peninsula industrial regions - Ni, Cu, Co, Zn (Fig. 4). Lake Kuetsjarvi features maximum concentrations o f Ni, Co and Zn in the sediment cores at a depth o f 2 to 4 cm (Fig. 5), particularly in the northern part o f the lake. The maximum o f Cd and Pb concentrations were noticed in the top layers of sediment cores. The similar vertical distribu­ tion (but with the lower concentrations o f Ni and Cu) was recorded in the sediments o f Lake Alla-Akkajarvi, which is ~45 km south o f melting furnaces of “Pechenganickel” Plant. Reduced concentrations of these elements within the top 2-cm-thick layer of bottom sediments in Lake Kuets­ jarvi may be explained by a change in the physicochemical conditions both in the lake and in its drainage basin, as well as by reduced emissions o f heavy metals by Pechenganikel’ Plant in the last decade. Unfortunately sediment dating was not carried out in the Kuetsjarvi, but it is possible to esti­ mate the sediment accumulation time o f the appropriate layers. The appreciable increase o f the contents o f the main polluted heavy metals (Cu, Ni) starts at 11, 12 and 8 cm depth (in Gulf Stream, Salmijarvi and White Stone aquatories o f the Kuetsjarvi, respectively), which should coincide with the beginning o f the anthropogenic loading o f the lake, i.e. 1932. 15