Chemical composition of lake sediments along a pollution gradient in a Subarctic watercourse / Dauvalter V., Kashulin N., Sandimiriv S. [et al.] // Journal of Environmental Science and Health. Part A. - 2011. - Vol. 46. - P. 1020-1033.

Downloaded by [Vladimir Dauvalter] at 21:54 24 November 2013 1024 Dauvalter et al. Lakes Ruskebukta and Skrukkebukta, respectively. Back­ ground concentrations o f heavy metals in sediments o f Lake Inari and Kuetsjarvi are o f approximately equal magni­ tudes, and similar to the levels observed in Lake Imandra in the central Kola region.[8,11] Long-term anthropogenic loadings on the watershed have led to environmental changes in the formation and chemical composition o f the lake sediments. Hence, back­ ground concentrations o f heavy metals play an important role for the definition o f influence o f anthropogenous in­ dustrial activity on water ecosystems. Vertical distribution o f elements in sediments By means o f sediment cores it is possible to investigate the history o f events having occurred in the catchment basin o f a certain lake, and to estimate background levels and changes in flow o f elements.[2] Such studies are especially relevant for regions with highly developed mining and m et­ allurgical industry, where abnormal distribution o f heavy metals is observed owing to geochemical features and in­ fluence o f pollution on the environment. Substantial increase in concentrations o f chalcophile el­ ements (Pb, Cd, Hg and As) in relation to background contents was revealed in surficial sediment layers o f Lake Inari (Fig. 2), and an appreciable increase in their concen­ trations was noted from sediment depths o f 5-10 cm. The increase in accumulation rate o f Pb is apparently caused by global pollution o f the atmosphere o f the No rthern hemi­ s p h e r e .^ Entrance o f Pb in many lakes is connected to its sedimentation from the atmosphere and from automobile exhausts.[20,26,29] Prohibition o f the use o f leaded gasoline during the last decades has led to a reduction o f Pb emis­ sions from exhaust gases and also to some reduction o f its contents in the uppermost sediment layers (Fig. 2). Small reductions in concentrations o f Cd in these layers at station 2 in Lake Inari and Hg at both stations o f the lake are also evident. Concentrations o f Ni, Cu, Co and Zn have in contrast to the chalcophile elements no t increased in the surficial sediment layers o f these stations, and also decreased or remained at the same level as the background values. De­ creases in concentrations o f Al, Na, K and Mg in surficial sediment layers o f Lake Inari were also observed. This fact can be connected with the receipt o f huge amount o f acid compounds which are emitted into the atmosphere by point sources (for example, the Pechenganickel and Severonickel Companies), and automobile exhausts. These compounds may cause processes o f water acidification, leading to en­ tering o f mobile elements from sediments to the water col- um n ,[15,30-32] and also to reductions in their contents during leaching o f soils in the catchment.[26] Significant changes were observed in the vertical distri­ bution o f concentrations o f Ni, Cu, Co and Zn in sedi­ ments o f lakes o f the Pasvik watercourse located upstream from the Pechenganickel smelters and Lake Kuetsjarvi, i.e., Hestefoss, Ruskebukta and Vaggatem (Fig. 3). These find­ ings coincide with results o f earlier sediment studies in Lake Vaggatem in 1988,[20] and in the lakes Rajakoski and Skogfoss, also located upstream from Lake Kuetsjarvi, in 1993.[33] However, as well as in the sediments o f Lake Inari, an appreciable increase in concentrations o f chalcophile el­ ements (Pb, Cd, Hg and As) in surficial layers compared to background levels was also revealed for the lakes Heste- foss, Ruskebukta and Vaggatem. The highest increase was noted for Hg (Hestefoss and Ruskebukta) and Cd (Heste- foss). This increase is probably no t directly connected to the activity o f the Pechenganickel Company, as this part o f the Pasvik watercourse is usually no t a subject to influ­ ence o f emissions o f heavy metals from the smelter activi- ties.[34] These findings thus confirm the conclusion o f many ecologists about a global environmental contam ination by chalcophile elements, especially in the Arctic and Subarctic zones o f the No rthern hemisphere.[35] Studies o f the chemical composition o f lacustrine sed­ iments in the catchment area o f the White Sea on the Kola Peninsula have revealed th at concentrations o f chal- cophile elements (Hg, Cd, Pb, and As) increase in all lakes examined, regardless o f contam ination sources, i.e., at­ mospheric pollution or wastes discharged from industrial enterprises.[36] In the lakes Bj 0 rnevatn and Skrukkebukta, located downstream the metallurgic smelters and Lake Kuetsjarvi, the maximum concentrations o f heavy metals were gener­ ally found in the top 1-cm sediment layer (Fig. 3). Contents o f Pb, however, decreased in the surficial 3 cm sediment of the lake Bj 0 rnevatn, and the maximal concentration was marked in 3-7 cm layer. Substantial increasing concentra­ tions o f heavy metals in relation to background values were noted from sediment depths o f 8 and 3 cm in Bj 0 rnevatn and Skrukkebukta, respectively. Considering that the Pechenganickel Company was the main source o f pollution in this region already 70 years ago, it was possible to estimate the sedimentation rate as approximately 1.1 and 0.4 mm /years in Bj 0 rnevatn and Skrukkebukta, respectively. Increasing contents o f organic m atter were observed from depths o f 6 and 2 cm towards the sediment surface in Bj 0 rnevatn and Skrukkebukta, re­ spectively. Reduction in concentrations o f K, Ca, Mg and Al towards the sediment surface o f the lakes Bj 0 rnevatn and Skrukkebukta is marked, which can be connected with input o f large amoun t o f sulphates in the sewage structure o f the Pechenganickel Company, causing desorption o f al­ kaline and alkaline earth metals and Al from suspended particles and sediments and their transfer to a soluble form. The contents o f sulphates in water o f the lakes Bj 0 rnevatn and Skrukkebukta are 2-3 times higher than in all other in­ vestigated lakes o f the Pasvik watercourse, except for Lake Kuetsjarvi. Very high concentrations o f the main polluting elements entering Lake Kuetsjarvi through River Kolosjoki are re­ flected by highly different sediment contam inations at the