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.

Downloaded by [Vladimir Dauvalter] at 21:54 24 November 2013 1030 Dauvalter et al. O 1000 2000 P, (ig/g Fig. 6. Vertical distribution of concentrations of P (pg/g, dry weight) in sediment cores from lakes in the Inari-Pasvik water course. increase in the contents o f biogenic element P in surficial sediment layers in some lakes o f the Pasvik watercourse can be related to the development o f eutrophication processes connected with input o f domestic sewage and regulations o f the water flow leading to reduced flow velocity, develop ments o f stagnation and, finally, accumulations o f nutrients in the water ecosystems. Phosphorus accumulated in sedi ments can be a source o f input o f this biogenic element in the water column.[40-42] In summary, the vertical distribution o f metals in sedi ments o f the investigated lakes allows us to study the his torical trends o f heavy metal inputs under the influence o f various anthropogenic factors. Active accumulation o f metals (in particular N i and Cu) is connected with the beginning o f the industrial activity in the No rthern p a rt of Fennoscandia. Global transfer o f air masses in No rthern hemisphere have, in contrast, likely caused the increased accumulation o f chalcophile elements (Pb, Cd, Hg, As) in the top layers o f lake sediments. Distribution o f elements in surficial layers o f sediments Emissions o f heavy metals into the atmosphere from the Pechenganickel Company and sewage runoff from smelters and refineries, tailing dams, slag piles and mines are the main sources o f the increased concentrations o f heavy metals in surficial sediment layers o f the Inari-Pasvik wa tercourse. This process is especially intensive in the lakes Kuetsjarvi and Bjornevatn. Water in the Inari-Pasvik sys tem is characterized by neutral pH values and possesses sig nificant neutralizing abilities in relation to the huge amount o f acid compounds entering from the smelting activity. This fact promotes accumulation o f mobile heavy metals (for example, Ni, Cu, Cd) in sediments.[43] Prevailing southwest winds distribute the tail o fpo llu tion mainly to the northeast direction (sediments in lakes on distance more than 20 km to the south from Nickel are almost unpolluted).[8,20] The fallout o f these elements in terms o f atmospheric precipita tion is small in No rthern parts o f Norway and F inland.[44] In these places, emissions o fth e smelters only slightly affect the heavy metal content o f top layers o f sediments.[5,8,10,45] The highest concentrations o f N i and Cu, exceeding background values with 10-380 times, have been observed at distances up to 10 km from the Pechenganickel Com- pany.[8] The excess o f background concentrations decreased up to 3-7 times at distances from 10 to 40 km from the pol lution source. Concentrations o f Co were 4-10 times higher than background values at distances up to 15 km from the pollution source and up to 3 times higher than in other lakes, confirming the large influence o f emissions from the smelters. The main part o f the industrial sewage from the Pechen ganickel Company enters Lake Kuetsjarvi, in which the maximum concentration o f all investigated heavy metals in surficial sediment layers was observed (Table 2). A similar observation was also made by earlier studies carried out in these systems.[7, 8 18] The highest concentrations o f heavy metals have been found at the deepest station 9 (Ni, Co, Cd, Hg), as well as at station 7 (Cu, Pb) located closest to the place o f sewage input from the Pechenganickel Com pany, but also at station 8 (Zn, As) located close to the channel connecting Lake Kuetsjarvi and the main stem o f the Pasvik watercourse. In downstream parts o f the Pasvik watercourse, espe cially in Lake Bjornevatn, significant accumulations o f Ni, Cu, Co, Zn, Cd and As were recorded, apparently con nected with the input o f polluted water from Lake Kuets- jarvi. In sediments o f Lake Inari, and also o f other lakes located upstream in the Pasvik watercourse, some surficial sediment concentrations o f Ni, Cu, Co and Zn in excess o f background levels were noted, except for N i and Cu in Lake Vaggatem (Table 2). An increase in the concentrations o f chalcophile elements (Pb, Cd, As, Hg) was recorded in the top sediment layers o f Lake Inari and lakes in the upstream part o f the Pasvik watercourse (Table 2). Among these lakes the highest con centrations o f chalcophile elements were noticed in Lake Inari, except for Hg, which had the highest concentrations in Ruskebukta and Hestefoss, probably connected with as pects o f flow regulation, formation o f storage pools, and accumulation in organic Hg compounds, mainly methyl mercury. This pattern confirms that the atmospheric emis sions o f the Pechenganickel Company are no t the main pollution source o f chalcophile elements. These sources are likely related to long-transported at mospheric pollution and can be situated in other parts o f Fennoscandia, or even in the central industrial areas o f Eu rope. Tetraethyl lead (knock-sedative dope in gasoline) is also the main source o f exceeded Pb contents in the environ ment. Other explanations for the increased concentration o f chalcophile elements are connected with their emissions into the atmosphere by smelters, although in rather small amounts (some tons per year).[34] As chalcophile elements has lower temperatures o f fusion than Ni, Cu, Co and Zn, they practically entirely transfer into aerosol structures

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.