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.

age background concentrations o f heavy metals in the Paz System Lakes and Lake Imandra (the largest lake o f the Kola Peninsula) are approximately equal (Moiseenko et al., 2002), excluding Hg, Pb, Cd (in 1.5, 1.8 and 20 times less than in Lake Imandra) and Co (in 1.7 times higher than in Lake Imandra). Table 1. Background concentrations o f heavy metals and As (^g/g, dry weight) in sediment cores o f the investigated Paz River parts Lake Cu Ni Zn Co Cd Pb As Hg Bjornevatn 42 58 100 27 0.11 11.2 3.36 0.003 Vaggatem 55 58 126 30 0.08 9.2 6.01 0.015 Ruskebukta 62 63 112 26 0.09 12.4 4.37 0.038 Skrukkenbukta 58 64 123 25 0.09 14.0 3.95 0.021 Hestefoss 36 46 100 21 0.05 6.8 3.95 0.021 Average 51 58 112 26 0.08 10.7 4.32 0.020 Minimum 36 46 100 21 0.05 6.8 3.36 0.003 Maximum 62 64 126 30 0.11 14.0 6.01 0.038 Standard deviation 11 7 12 3 0.02 2.8 1.01 0.013 2.2. Vertical Distribution of Heavy Metals in Bottom Sediments The vertical distribution o f concentrations of Ni, Cu, Co and Zn in the sediments o f parts Ruskebukta and Hestefoss varies only slightly (Fig. 2). However, in these aquatories , the con­ centration o f Cd, Pb, As and Hg in the top layers o f the sediments is substantially higher than that o f the background. It is unlikely for this elevated concentration to be due to the Pechen- ganikel’ Plant operation, since this part o f the drainage basin o f the Paz River is only slightly af­ fected by emissions o f heavy metals from the plant. In Lake Bjornevatn, the maximum concentrations o f heavy metals (except for Pb) were recorded in the upper 1-cm-thick layer o f bottom sediments. The Pb content o f bottom sediments de­ creases from bottom to top. Heavy metal concentrations elevated relative to the background val­ ues occur at a depth o f 7 - 8 cm and lower. Taking into account that the “Pechenganickel” Plant has been the main source o f pollution in this region for as long as 60 years, one can assess the rate o f deposition (~1 mm/year). Almost the same situation is in the sediment core o f the Lake Skrukkenbukta, situated downstream o f the Paz River and polluted in lower degree , but the sedimentation rate is much smaller — 0.3 mm/year (see distribution of Cu and Ni in Fig. 2). Concentrations o f the almost all investigated polluted elements (excepting Zn and Co) in the sediment core o f the Vaggatem, situated upstream of the Paz River from the entrance o f sewage waters o f the Pechenganickel Company through the Salmijarvi, increase towards to the sediment surface (Fig. 2) in 1.3 - 2.9 times in comparison with the background values. 2.3. Distribution of Heavy Metals in the Top Layers of Lake Sediments Emissions of heavy metals and wastewater from melting furnaces, slime pits, tailing dumps, and mines o f the Pechenganikel’ Plant are the main sources o f increased concentrations o f Ni, Cu, Co and Zn in the top layers o f sediments in Lakes Bjornevatn and Skrukkenbukta (Fig. 3). The water o f the Paz water system features neutral pH values and considerable neutralizing capacity with respect to acid compounds, which abundantly arrive from the plant. This greatly favours 11