Eight catchments, from 15-35 km2 in area, have been studied as part of an ecogeochemical mapping programme in an area extending from 24oE to 35o30' and S to the Arctic Circle in Finland and the S border of Murmansk region in Russia. The main aims of the project have been to study the distribution of heavy metals at regional and local scales and to distinguish anthropogenic from natural concentrations.
Three catchments, one 10 km NE of Zapolyarniy (1) and two, respectively 5 and 25 km S of Monchegorsk (2 and 4) show high levels of deposition of heavy metals, especially Ni and Cu, and S, related to the metallurgical industry in these cities. The plant in Zapolyarniy processes local ore and the plant in Monchegorsk has predominantly processed ore from Noril'sk notable, i.a., for its high content of platinum metals (PGE). The Noril'sk ore has, in general, Cu>Ni and Pd>Pt>>RhªAu. The Pechenga ores have a Ni:Cu ratio of c. 2:1 and a PGE content 1-2 orders lower than Noril'sk ore.
Catchment 2 (22.5 km2 ) lies within the area of technogenic desert around Monchegorsk: its bedrock includes mafic rocks but no known mineralisations. Bedrock and C-horizon soil samples have normal acid-leachable Ni and Cu contents for the rock types. 25 topsoil samples, from sites evenly distributed over the catchment, have mean contents of Ni and Cu 1-2 orders of magnitude higher than the C-horizon samples, which, taken with data from other media, provides strong evidence for the anthropogenic origin of the heavy metals. The same topsoil samples show geometric mean total contents for the noble metals analysed (by graphite furnace-AAS - Niskaara and Kontas, 1980) of: 1.4 ppb Rh, 49.6 ppb Pt, 187.6 ppb Pd and 9.5 ppb Au. The maximum values are 13.2, 466, 1760 and 99.5 respectively. These values are unusually high, well in excess of values found above known PGE-mineralisations elsewhere (Wood and Vlassopoulos, 1990). The pattern of concentration of the noble metals closely matches that found in published averages for ore from the Noril'sk -Talnakh mineralizations (Naldrett, 1989), though 1-2 orders of magnitude lower. This clearly shows that the noble metal contents of the topsoil are also anthropogenic, and suggests that they emanate from the plants in Monchegorsk at an early stage in treatment of the ore, probably as a minor component of Ni-Cu rich particles..
Topsoil samples from catchment 4 have geometric mean total contents of 22.1 ppb Pd and 1.8 ppb Au, also highly anomalous and much as would be expected, given the greater distance of catchment 4 from Monchegorsk (these samples were not analysed for Rh and Pt). Values of Ni and Cu in topsoil in catchment 4 are lower than those found in catchment 2 by similar orders of magnitude.
Topsoil samples from catchment 1, NE of Zapolyarniy have Ni contents 2-4 times their copper content and have Pd contents close to the detection level or below, indicating a geometric mean value of c. 1 ppb, clearly reflecting the different composition of the ore being processed.
Naldrett, A.J., Magmatic Sulphide deposits. Oxford monographs on geology and geophysics, No. 14, Oxford (1989).
Niskavaara, H. & Kontas, E., Analytica Chimica Acta 231, 273-282 (1980).
Wood, S.A. & Vlassopoulos, D., Can. Mineral. 28, 649-664 (1990).