Lake water geochemistry on the western Kola Peninsula, north-west Russia

Applied Geochemistry 14 (1999) 787±805

Lake water geochemistry on the western Kola Peninsula, north-west Russia Clemens Reimann a,*, David Banks a,b, Igor Bogatyrev c, Patrice de Caritat a,d, Galina Kashulina e, Heikki Niskavaara f a Geological Survey of Norway, N-7491 Trondheim, Norway Holymoor Consultancy, 86 Holymoor Road, Holymoorside, Chester®eld, Derbyshire, S42 7DX, UK c Kola Geological Information Laboratory Centre, Fersman St. 26, 184200 Apatity, Russia d CRC LEME, c/- Australian Geological Survey Organisation, GPO Box 378, Canberra, ACT 2601, Australia e Kola Science Centre, INEP, Fersman St. 14, 184200 Apatity, Russia f Geological Survey of Finland, P.O. Box 77, 96101 Rovaniemi, Finland b

Received 31 July 1998; accepted 27 December 1998 Editorial handling by R. Fuge

Abstract Water samples were taken from 120 lakes spread over the western half of the Kola Peninsula, NW Russia. The samples were analysed for 37 elements, pH and electrical conductivity. Lake water chemistry appears in most cases to be dominated by a Ca/Na±HCO3 signature, characteristic of natural carbonate/silicate weathering. Input of elements from marine derived salts and from the Ni industry (roasting plant at Zapoljarnij, smelter at Nikel and smelter/re®nery at Monchegorsk) emissions are restricted to limited regions. Considering that 3 of the world's largest point source emitters of SO2 are located within the area, the median lake water pH is surprisingly close to neutral (6.6, range 4.2±7.4). Indeed some of the apparently SO4 contaminated lakes nearest to the smelters yield the highest pH values. Changes in climate and vegetation from north to south within the survey area probably have an in¯uence on element concentrations and pH as observed in the lake waters. Proton displacement by sea salt cation input provides an explanation of low pH lakes in coastal areas. # 1999 Elsevier Science Ltd. All rights reserved.

1. Introduction The Geological Surveys of Finland (GTK) and Norway (NGU) and the Central Kola Expedition (CKE) in Russia are carrying out a major geochemical mapping project (see World Wide Web site http:// www.ngu.no/Kola) in a 188 000 km2 area north of the Arctic Circle, comprising the entire area between 248

* Corresponding author. E-mail address: [email protected] (C. Reimann)

and 35.58 E, north to the Barents Sea (Fig. 1). The project started in 1992, mapping a 12 000 km2 sub-area around the Ni smelter at Nikel (Chekushin et al., 1993; Reimann et al., 1996b, AÈyraÈs et al., 1997a; Niskavaara et al., 1996), continued in 1994, studying 8 small catchments throughout the survey area (AÈyraÈs et al., 1995; de Caritat et al., 1996a, 1996b, 1997a, 1998a, 1998b Reimann et al., 1997a, 1997c), and ®eld work concluded in the summer and autumn of 1995 with the sampling of terrestrial moss, topsoil (0±5 cm), organic topsoil (humus 0±3 cm or less if the organic layer was thinner than 3 cm) and complete podzol pro®les (5

0883-2927/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 8 8 3 - 2 9 2 7 ( 9 9 ) 0 0 0 0 6 - 2

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Fig. 1. Location of the study area. The area outlined in black shows the whole study area of the Kola Project, lake water was only collected in the Russian part of the area. Major cities and industrial sites are given. The numbers 1±8 refer to the catchments sampled during the catchment stage of the Kola Project (for further data see Table 2). The wind rose for the Monchegorsk area is from MaÈkinen (1994), more detailed meteorological maps as well as a geological map are given in Reimann et al. (1998).

horizons) throughout the survey area at an average density of one sampling station per 300 km2. The whole data set describing the regional distribution patterns of up to 50 elements in 5 di€erent sample media is available in the form of a geochemical atlas (Reimann et al., 1998). Data obtained so far show that the survey area, in terms of atmospheric chemistry, combines some of the most pristine environments in the whole of Europe (NW Finland, N Norway) with some of the most contaminated sites (Nikel/Zapoljarnij and Monchegorsk) (AÈyraÈs et al., 1997b; Reimann et al., 1996b, 1997a, 1997b, 1997c). In addition to the above-named media, lake water samples were collected at 120 sites in the Russian part

of the project area to create a link to the Scandinavian 1000±lakes project (Henriksen et al., 1996, 1997; SkjelkvaÊle et al., 1996a, 1996b). Results of the Kola lake water analyses presented here are not included in the above mentioned atlas (Reimann et al., 1998). The western part of the Kola Peninsula has been a large industrial centre for Ni mining and smelting for about 60 a. Some of the world's largest point sources of SO2 emissions are located within the study area (Gunn et al., 1995): namely the Ni smelter at Nikel, the ore roasting plant at Zapoljarnij and the Ni smelter and re®nery at Monchegorsk (Fig. 1), together accounting for atmospheric emissions of about 300 000 t of SO2, 15 000 t of NO2, 1900 t of Ni, 1100 t of Cu

C. Reimann et al. / Applied Geochemistry 14 (1999) 787±805

and 94 t of V2O5 yearly (Murmansk Regional Committee for Ecology and Natural Resources, see Reimann et al., 1997c). The annual Ni, Co and Cu emissions alone represent a monetary value of close to US$ 20 million. The smelters use di€erent technologies and process di€erent ore types (the ore roasting plant in Zapoljarnij uses local Pechenga ore only; the Ni smelter in Nikel uses local Pechenga ore and occasionally Norilsk ore imported from Siberia; the much larger smelter/re®nery in Monchegorsk uses mostly Norilsk ore and some Pechenga ore as well as the products of the Nikel smelter for further re®ning) which result in di€erent emission characteristics and di€erent suites of emitted elements (Boyd et al., 1997; Reimann et al., 1997c). Severe damage to the terrestrial ecosystem of this area can be detected by satellite imagery (Tùmmervik et al., 1995). Limited areas (up to 1000 km2) around the main smelters in Nikel and Monchegorsk and the roasting plant in Zapoljarnij must be classi®ed as devastated `industrial desert'. In these areas the soils are no longer able to retain heavy metals or base cations which are consequently washed out to the aquatic environment (de Caritat et al., 1996b; Niskavaara et al., 1996, 1997). This e€ect peaks at snow melt in late April/early May each year and is least pronounced during the summer months when sampling of the lakes took place. The climate is very harsh on the Kola Peninsula with long winters (6±8 month with continuous snow cover) and short summers with 24 h daylight. Average precipitation is rather lowÐless than 500 mm per year over large parts of the area, with maximum precipitation during winter (see maps in Reimann et al., 1998). The geology of the area is complex (see map in Reimann et al., 1998), ranging from quartzites and granites through metasediments, felsic and ma®c granulites, gneisses, amphibolites and basalts to ultrama®c alkaline intrusives, with gneisses as the dominant lithology. Di€erent rock types can contain very di€erent element concentrations (see Reimann and de Caritat, 1998; for in¯uence on water chemistry: Morland et al., 1997, Banks et al., 1999). Most unusual in terms of chemical composition are the alkaline intrusions near Apatity in the Russian part of the project area. Di€erences in bedrock composition may result in quite large di€erences in the natural element contents in local soil and groundwater (Reimann et al., 1996a, 1997a; de Caritat et al., 1998b) and strongly in¯uence surface water chemistry (de Caritat et al., 1996a). Former investigations of lake water chemistry in the area have focused on water quality issues, lake water acidi®cation and so-called critical loads (Moiseenko, 1994; Moiseenko et al., 1995). In general only concen-

789

trations for the major anions and cations and, in addition, Cu and Ni, were previously reported (about 20 parameters in total). Here the authors concentrate on large scale factors in¯uencing the regional distribution of 37 elements, pH and electrical conductivity as measured in 120 water samples taken from lakes throughout the western half of the Kola Peninsula. The regional distribution is presented in maps, while factors in¯uencing the observed concentration patterns are discussed and compared with results obtained from other sample media (e.g., moss, representing atmospheric input, the C-horizon of podzols, representing the geogenic background, stream water and rain water composition from single catchments within the area). Results are compared with those of other regional surface water surveys in northern Europe and from Sudbury, Canada. 2. Methodology 2.1. Sampling The selection of lakes sampled followed as closely as possible the criteria used for the ``Nordic lake survey 1995'' (Henriksen et al., 1996, 1997). Due to logistic reasons the samples had to be taken in July, while the samples for the Nordic lake survey were taken during the autumn lake turnover. This may render direct comparison of the absolute values between the two studies problematic. However, it has been demonstrated (de Caritat et al., 1996b) that regional variations in surface water geochemistry in the area are much larger than temporal variations (with the possible exception of the snow melt peak in April/May). Lake selection was based on lack of local anthropogenic point sources (e.g., waste water). The climate precludes large scale agriculture in the area. Samples were taken as close to the outlet of the lakes as practically possible. At each site one 500 ml polyethylene (PE) bottle and one 100 ml PE bottle were ®lled with lake water. All bottles were factory new. The sampler was wearing PE gloves for sampling. The bottles were ®lled with water by holding them several centimetres under the water surface. Before sampling each bottle was thoroughly rinsed three times with lake water (AÈyraÈs and Reimann, 1995). The lake water samples were not ®ltered nor acidi®ed in the ®eld in keeping with the sampling protocols of the ``Nordic lake survey'' (Henriksen et al., 1996). This complicates direct comparison of the lake water results with those of other water surveys of the Kola project, where all waters were ®ltered at <0.45 mm and ®eld acidi®ed (e.g., rain ± Reimann et al., 1997c; ground water ± de Caritat et al., 1998b and stream water ± de Caritat et al., 1996a, 1996b) and where snow

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(Reimann et al., 1996b, de Caritat et al., 1998a) was delivered frozen to the laboratory and ®ltered while thawing. 2.2. Analysis All samples were analysed at the laboratory of the Geological Survey of Finland (GTK). The 5 anions ˆ Br±, Clÿ, Fÿ, NOÿ 3 and SO4 were determined by ion chromatography (IC) from the 500 ml samples. In addition, pH was determined by a pH electrode and electrical conductivity by potentiometry. Inductively coupled plasma-atomic emission spectrometry (ICP± AES) was used to determine Ca, Mg, Na, P, S and Si concentrations from the 100 ml samples after laboratory acidi®cation with HNO3. All other elements were measured from the same samples (100 ml acidi®ed) by inductively coupled plasma-mass spectrometry (ICP± MS): Ag, Al, As, B, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, K, Li, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sr, Th, Tl, U, V and Zn. Alkalinity was unfortunately not measured directly but was subsequently calculated assuming ionic balance: Alkc ˆ …Na‡ ‡ K ‡ ‡ Ca‡‡ ‡ Mg‡‡ † ÿ ÿ ÿ…Clÿ ‡ SOˆ 4 ‡ NO3 ‡ F † with all concentrations expressed in meq/l. It is likely that hydrogen carbonate ions (HCO3ÿ) are the dominant contributor to alkalinity, but contributions from other species, including organic (e.g., humic-type) anions cannot be discounted. The alkalinity calculation is strongly dependent on the accuracy of determinations of the other species used in the equation. A plot of Alkc vs. pH (see Fig. 9) shows a classic titration-type curve, which may be interpreted as an independent con®rmation of the validity of the alkalinity calculation.

terials SLRS±2 and SLRS±3 from the National Research Council, Canada, and Standard Reference Materials 1643c and 1643d (trace elements in water) from the National Institute of Standards and Technology, USA, were used to check for trueness of the results. Obtained values were in very good agreement with those certi®ed for the respective standard (de Caritat et al., 1998a). In addition, sample blanks, an in-house water standard and sample duplicates were run at a rate of 1 in 10. 2.4. Data analysis All graphics and maps were produced using the 1 DAS program (Dutter et al., 1992), based on exploratory data analysis (EDA) methods (Tukey, 1977; Velleman and Hoaglin, 1981). KuÈrzl (1988), Reimann et al. (1988), Rock (1988) and O'Connor and Reimann (1993) give an introduction to the advantages of using exploratory data analysis methods when dealing with geochemical data. An explanation of all techniques used here is given in Reimann et al. (1997b) and Reimann et al. (1998). The construction of the box plot follows Tukey's (1977) original de®nition (whiskers to last real data point up to 1.5  hinge spread), data outliers are marked by squares (>1.5  hinge spread) or plusses (far outliers->3  hinge spread). Coincidence of the median and one (or both) of the hinges is marked by a cross. The notches (square brackets), placed at 1.58  (hinge spread/Z(n )) on either side of the median, are a test of signi®cance of medians from di€erent populations or boxes. Values below detection were set to one half the detection limit for the purpose of graphical data analysis. Class selection for mapping is based on the boxplot as well (for an explanation of the technique see Reimann et al., 1998).

2.3. Quality control

3. Results

Contamination is a serious issue when analysing waters with several elements in the low ppt range. For this project all ®eld equipment needed was shipped from Norway to Russia. Factory new PE bottles, all from the same production batch, were used for sampling as suggested by Reimann et al. (1996a). Prior to sampling the bottles were packed and sealed in PE bags and handled with PE gloves only. GTK's laboratory is equipped with clean room technology and accredited to meet the requirements of the EN45001 standard and the ISO-guide 25. Calibration of ICP± AES and ICP±MS was performed by the arti®cal multielement calibration method based on solutions from SpexTM and MerckTM. Riverine water reference ma-

3.1. General water chemistry and comparison with results of other lake water studies Table 1 summarises the results of the lake water analysis for all elements/parameters. In Fig. 2 the results are presented graphically in the form of box plot comparisons, sorted after decreasing median concentration. Of the analysed elements, Na, Ca, Si, Clÿ, S, Mg and K are dominant in the lake waters in terms of mass (all with median concentrations >0.25 mg/l). If we include Alkc and convert concentrations in mg/l to meq/l, the dominant ions now become (in order of descending median concentrations in meq/l) alkalinity ++ ÿ + (HCOÿ , Na+, Mg++, SOˆ 3 ), Ca 4 , Cl and K . The

C. Reimann et al. / Applied Geochemistry 14 (1999) 787±805

791

Table 1 Analytical results of Kola lake water (n=120, this study) in comparison with results from other studies NW Russia Kola Peninsula this study (n=120) Element Ag Al As B Ba Be Bi Br Ca Cd Cl Co Cr Cu F Fe K Li Mg Mn Mo NO3 Na Ni P Pb Rb S SO4 Sb Se Si Sr Th Tl U V Zn pH Alkalinity EC a

method

min.

max.

ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS IC ICP-AES ICP-MS IC ICP-MS ICP-MS ICP-MS IC ICP-MS ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS IC ICP-AES ICP-MS ICP-AES ICP-MS ICP-MS ICP-AES IC ICP-MS ICP-MS ICP-AES ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS ICP-MS pH-Electr. calculated Potent.

<0.02f 5.76 <0.06 <0.5 0.69 <0.1 <0.02 <30 200 <0.02 400 <0.02 <0.2 0.17 <30 <30 80 <0.3 <200 0.28 <0.03 <30 800 <0.03 <200 <0.03 0.07 350 800 <0.02 <0.5 <100 4.5 <0.02 <0.01 <0.01 0.06 <0.2 4.2 0 1.3

0.2 1100 2.94 22.3 26.7 0.2 <0.02 160 8500 0.81 11300 16.9 5.76 152 230 1220 1770 1.67 2210 61.9 1.18 4490 12900 304 <200 4.76 2.93 6180 15000 0.15 0.9 4500 104 0.06 <0.01 0.68 3.02 20.1 7.4 525 8.8

median <0.02 47.05 0.12 1.37 4.27 <0.1 <0.02 <30 2000 <0.02 1440 0.04 0.29 0.94 50 70 370 <0.3 885 3.6 0.08 <30 2200 0.69 <200 0.07 0.53 1000 2700 <0.02 <0.5 1450 15.5 <0.02 <0.01 0.02 0.19 0.99 6.8 162 3.2

NW Russia Kola (n=370)a median

20

Norway

Norway North (n=205)c

Finland

(n=473)b

Norway South (n=207)c

(n=1172)d

Canada, Sudbury (n=97)e

median

median

median

median

median

16

127.6

<0.01 1.41 3.08 <0.01 <0.02

2500 1950 1.55 580 990 3 2400 1

4160

6.7 193 3.6

1070 <0.02 1600 0.053 <0.1 0.413 <40 60.7 210 0.17 390 3.43 <0.04 12 1300 0.328 3 0.18 0.49

620

1700

2500

2680

1600

2500

1000

220

<40

<40

110

290

500

77.8 280

180

590

800

81 990

4 1800

71 1400

3

3

1700 0.025

2000

1900

890 5.91 <0.015

1100

890

5.3 2 1.7

6.8 89 2.9

0.041 <0.3 1.7 6.4 38 2.2

Moiseenko et al., 1995, Kola lake water. SkjelkvaÊle et al., 1996a, Norwegian lake water. c SkjelkvaÊle et al., 1996b, lake water from south and north Norway. d Lahermo et al., 1995, Finnish lake water. e McNicol and Mallory, 1994, lake water from the Sudbury region, Canada. f All values in mg/l, exceptions: pH (pH units), alkalinity (meq/l) and electrical conductivity (EC) (mS/m). b

690 39.2 800 6.28

4100 1280

6.2 64 3.1

5.2

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Fig. 2. Chemical composition of Kola lake water, sorted in decreasing order of median concentration. For an explanation of the box plot see text. Unlabelled tick marks on log scale represent 2.5, 5 and 7.5 the closest, lowest value labelled.

typical (median) compositional type of the sampled lake waters is thus Ca/Na±HCOÿ 3 (see also Fig. 8). Iron, Fÿ, Al and Sr show concentrations between 10 ÿ and 100 mg/l. Nitrate (NOÿ 3 ) and Br fall probably into this concentration class as well, but there were too many results below the detection limit to establish a reliable median concentration for these two parameters. The elements Ba, Mn, B, Zn, Cu, Ni, Rb, Cr, V and As all have median concentrations between 0.1 and 10 mg/l. Lithium and Se may fall into this class as well. Median concentrations below 0.1 mg/l are typical for the elements Mo, Pb, Be, Co, U, Cd, Ag, Sb, Th, Bi ÿ and Tl. For NOÿ 3 , Br , Se, Be, Cd, Ag, Sb, Th, Bi and Tl most of the results (>75%) were below the respective limit of detection. Concentration ranges cover 2±3 orders of magnitude for most elements (Fig. 2). Most

elements show rather tight boxes (the inner 50% of the data), whilst Cr, Fe, Mn, Ni, Mo and U show unusually wide boxes re¯ecting large spread in concentrations even for the inner 50% of the data. All elements other than Fe, Mn, Li, Mo and U have either lower or upper (or both) data outliers (as de®ned by Tukey, 1977). NOÿ 3 , Cu, Ni and Co are characterised by single very extreme (`far' ± Tukey, 1977) upper data outliers. This behaviour is also expressed by the maximum/median ratio for the lake waters for Ni (441), Co (423), and Cu (163)Ðthe maximum concentration is here more than one hundred times higher than the median. The next two elements with a rather large maximum/median ratio are Cd (81) and Pb (68). The ®rst group of elements are all major pollutants from the Russian Ni industry. The maximum Cd concentration

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was measured in a lake near Monchegorsk, Pb was highest in a lake near Kovdor, where Fe ore is mined and milled. Although these two elements are not emitted in major quantities (Reimann et al., 1996b, 1997a, 1997c, 1998), their regional distribution still appears to be in¯uenced by industry. When comparing these results with the chemistry of Fennoscandian lake waters sampled in other studies (Lahermo et al., 1995; Moiseenko et al., 1995; SkjelkvaÊle et al., 1996a, 1996b), it is noteworthy that the median concentrations of major parameters are of the same order of magnitude (Table 1). It is also interesting to note that the results from lakes on Kola, regardless of whether they were sampled in summer (this study) or during the autumn turnover (Moiseenko et al., 1995), are more comparable in terms of major ion chemistry with other lake waters from unpolluted northern Norway (SkjelkvaÊle et al., 1996b) than with lakes from southern Norway (Table 1). This observation indicates that natural factors common to the Northern lakes (geology, climate, vegetation, distance to coast) may be more important in determining lake water chemistry than anthropogenic factors. Compared to results from lakes near Sudbury (McNicol and Mallory, 1994), a large Ni mining and smelting centre in Canada, the Kola lakes are enriched in Clÿ and Na, which can be ascribed to the coastal position of the Kola Peninsula compared to the continental location of Sudbury. The Sudbury lakes show clearly higher concentrations of Mn, Ni, Al and Ca when compared to the Kola results. This is probably partially related to the considerably lower pH of these lakes (median: pH 5.2, compared to Kola: pH 6.8). Another factor in¯uencing the measured element concentrations may be di€erent weathering rates due to the di€ering climatic conditions. Results from another study of Kola lake waters (Moiseenko, 1994) are generally quite comparable to the results presented here, although the SOˆ 4 values reported by Moiseenko are considerably higher and the Cu and Ni concentrations are slightly higher than the median concentrations reported here. This may be caused by di€erent production and thus emission levels of the Kola smelters in 1990/92 and 1995. 3.2. Regional distribution of elements and regional trends in water chemistry To further determine element sources and dispersion characteristics, the analytical results were mapped and plotted on pro®les (north-south from the Barents Sea through Monchegorsk to the White Sea and east-west from the Norwegian/Russian border near Nikel to the eastern project border). Fig. 3 shows regional distribution maps for As, Cu, Ni and S. The distribution of all 4 elements is governed by the high input from the

793

main pollution sources at Nikel/Zapoljarnij and Monchegorsk to the lake waters. At the same time geogenic sources can be detected for As in the southeastern corner of the project area and for Cu and Ni in the north-eastern part of the project area. It is interesting to note that the input of S via sea spray in the coastal areas is considerably less obvious on the map than, for example, the input of Cl and Na. Maximum values for As occur at Nikel, while for Cu, Ni, and S they occur near Monchegorsk. At ®rst glance this is surprising in so far as Nikel/Zapoljarnij combined have much higher total S emissions than Monchegorsk; this is, for example, clearly re¯ected in the humus map (Reimann et al., 1998). Recent mineralogical investigations of ®lter residues of snow samples from the surroundings of Zapoljarnij have shown, however, that much of the S from this plant is emitted in the form of ®ne sulphide ore particles, while no ore particles but rather metal rich sulphide and oxide globular phases are emitted at Monchegorsk (Gregurek et al., 1998, 1999). Emitted S-rich particles may thus be di€erently bound due to the large di€erences in the technological processes used at these sites and consequently di€erent amounts are reaching the aquatic environment at di€erent times. The importance of the input of sea salts becomes visible in maps for B, Cl and Na (Fig. 4). At the same time it is apparent that some B and Na are released from the smelter at Monchegorsk (see for instance de Caritat et al., 1996a). The signi®cant Clÿ-emissions from Monchegorsk (300 t/y ± MRCENR, 1995) and discharges to surface water (17 000 t/y ± Pozniakov, 1993) are hardly re¯ected in the lake water chemistry. Concentrations of Sr in sea water are also much higher than those in most fresh waters and one would expect to detect the input of sea spray in coastal areas in a regional map of Sr. The map for Sr, however, is governed by geogenic sources related to the alkaline intrusions occurring near Kirovsk (Khibiny/Lovozero), which cause a regional scale Sr-anomaly in the C-horizon of podzols (Reimann et al., 1998). The lowest Sr concentrations within the whole area are actually observed along the coast. This provides evidence that groundwater in¯ux rather than rain water input was the governing factor for lake water chemistry at the time of sampling. Fig. 5 presents maps for pH, Ca, K and Mg. The pH map is surprising in that very few regional patterns may be discerned. While one low pH outlier is located near Monchegorsk most lakes near industry exhibit pH values above the median (pH 6.8). The most striking regional feature is the many low pH values in the Barents coastal zone. Rosenqvist (1978) hypothesized that input of sea salt cations to soil pro®les during storm events displaces protons from exchange sites thus providing a mechanism for surface water acidi®-

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Fig. 3. Geochemical maps of As, Cu, Ni and S in Kola lake water. Class selection for mapping according to the boxplot (for mapping techniques used refer to Reimann et al., 1998).

cation episodes. The present data suggest that this mechanism may also cause sustainable regional pH distribution patterns. Ivarsson and Jansson (1995) studied the controls on acidity in running waters in Central Northern Sweden and concluded that the organic acid and corresponding basic organic anion bu€ering system were the most important systems controlling pH. The leaching of organic acids from soil pro®les can be strongly enhanced in the damaged soils in the immediate surroundings of the metal smelters, which factor might explain the high variability of lake pH values observed near Monchegorsk. In addition di€ering organic acid-base bu€ering systems, related to the 3 vegetation zones which the project area encompasses (Reimann et al., 1998) may provide an alternative explanation for the regional pH distribution. There is little obvious pattern to the regional distribution of the alkaline earth metals (Ca, Mg), although some tendency to increased Mg values in the Barents coastal zone is detectable (Fig. 5). Ma®c and ultrama®c lithologies occurring near Monchegorsk are not

re¯ected in the Mg distribution, suggesting that geology alone is insucient to explain the generally high pH lake water values around Monchegorsk. The distribution of K is dicult to explain; there appears to be little correlation with nitrate (not shown), negating anthropogenic sources as an explanation. It is possible that the distribution of the high outliers is partially ascribable to the occurrence of basic alkaline igneous rocks near Apatity. Sources and behaviour of elements are easier to study in the pro®les, which can be cut out of the main data set in di€erent directions. Fig. 6 shows such pro®les for Clÿ, Cu, Ni, S, pH, Al and K in a north-south direction from the coast of the Barents Sea through Monchegorsk, the White Sea and to the Arctic Circle, the southern project border. Elements such as Clÿ (Fig. 6) and Na (not shown) are strongly in¯uenced by the input of sea salts at the coast of the Barents Sea. This input of elements as dry or wet fallout of marine aerosols is clearly detectable in the lake water chemistry for about 100 km inland. In contrast, this e€ect is

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Fig. 4. Geochemical maps of B, Clÿ, Na and Sr in Kola lake water.

hardly visible at the coast of the White Sea. Emissions at Monchegorsk are visible as `humps' in both the Clÿ and the Na (not shown) pro®les. Copper and Ni show the in¯uence of anthropogenic emissions at Monchegorsk on lake water chemistry. In both north and south directions, elevated Cu and Ni concentrations in lake water can be detected over a distance of 100 to 150 km from source. This is in good agreement with observations made when using other sample media (e.g., moss and humus ± see Reimann et al., 1998). Note that the main wind direction in this area is north-south (Fig. 1) as a result of a funnel e€ect due to the local topography around Monchegorsk. Considering the large quantities of metals emitted at Monchegorsk (1600 t Ni and 940 t Cu in 1994 ± Reimann et al., 1997c), however, the metals concentrations near the emission sources seem rather modest. The contrast between background values (e.g., the median concentrations) and maximum concentrations observed is seldom greater than 100 (up to 441 for Ni and 163 for Cu ± see above) and in general less than 10. This contrast is much higher in other

media: for Cu and Ni it often reaches 500 to more than 1000 (e.g., moss ± AÈyraÈs et al., 1997b; stream water ± de Caritat et al., 1996a; topsoil ± Reimann et al., 1997a; rainwater ± Reimann et al., 1997c). Comparable pro®les drawn for moss and humus show a much more pronounced increase in heavy metals towards Monchegorsk (Reimann et al., 1998). Although this e€ect may be partly caused by a higher sample density of these other media, it still seems that heavy metals are to a large extent bound to vegetation and soil and reach surface waters only in a very limited region. Moiseenko et al. (1995) noted elevated Cu and Ni concentrations in waters and lake sediments in a 30 km zone around Monchegorsk. The pro®le for S shows the emissions at Monchegorsk to be the most important in¯uence on the regional distribution, while the input of sea spray S along the northern coast appears comparatively insigni®cant. However, the area strongly a€ected by industry again appears rather small, especially considering that Monchegorsk is one of the largest point-source emitters of SO2 on a world wide scale. It is very inter-

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Fig. 5. Geochemical maps of Ca, K, Mg and pH in Kola lake water.

esting to directly compare the S pro®le with the pro®le for the lake water pH. Obviously, the input of S has, as such, no major `acidifying' e€ect on the lake waters (only one lake near Monchegorsk has a pH < 6). The most neutral and even basic lake water pH values (up to pH 7.4) were observed within the area receiving the highest S deposition. The apparent acidi®cation of surface waters in some areas of Scandinavia is often ascribed to the phenomenon of `acid rain', usually attributed to anthropogenic emissions of S (and N) oxides, such as from the smelters and ore-roasting plants on Kola. Analyses of Scandinavian rainfall often exhibit signi®cant non-marine concentrations of NO3 and SO4. The acid in precipitation is, sensu strictu, protons (H+, which are often assumed to balance non-marine SO4 or NO3 anions in `acid rain'), although the term acid is usually taken to include other species releasing protons on hydrolysis (SO3, NOx) or oxidation (NH‡ 4 or pyrite FeS2). The deposition of protons may be bu€ered by (a) a number of oxide, hydroxide, carbonate and silicate

mineral phases in the soil, (b) by adsorption on cation exchange sites in the soil or (c) by hydrogen carbonate or even organic anions (Ivarsson and Jansson, 1995) in ground- or surface-waters. In the Kola area, potential agents for acidi®cation include protons dissolved in precipitation and fallout of ®ne sulphide particles some of which (FeS2) may release protons on oxidation. Fig. 6 con®rms that the ore-processing industry appears to have resulted in a sub-regional SO4 enrichment in some lake waters on Kola. Almost none of the lakes sampled in the survey area were found to be acid, with the exception of 1 lake near Monchegorsk and 2±3 lakes spread all over the area and with no apparent relation to industry. On the contrary, Fig. 6 con®rms that both the generally highest and lowest pH values occur in the immediate vicinity of Monchegorsk. There is also no evidence of generally elevated Al concentrations in the lakes near Monchegorsk (apart from 1 or 2 lakes), which fact is likely to re¯ect the low solubility of Al at circumneutral pH. At the same time the lake waters appear to

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797

Fig. 6. N±S pro®les (with smoothed trend lines) for Clÿ, Cu, Ni, S, pH, Al and K, starting at the coast of the Barents Sea, cutting the Ni smelter at Monchegorsk and ending at the Polar Circle. Note that Monchegorsk is taken as the "0"-distance to simplify the study of the in¯uence of industry on regional lake water composition. The Barents Sea coast is to the left in these pro®les. The locations of Apatity, Monchegorsk and Murmansk are marked in the index map.

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show the highest variation in pH near Monchegorsk. A number of tentative explanations may be forwarded for this surprising e€ect:

sample media taken during di€erent phases of the Kola project, is presented in Table 2. Near Zapoljarnij/Nikel, precipitation is by no means more acid than in the background areas Table 2, in snow meltwater, a pH of up to 7.5 was previously reported near Zapoljarnij (Reimann et al., 1996b). Rain is most acid near Monchegorsk (pH 4 compared to pH 4.7 in the background areas), but this is not re¯ected in stream or lake waterÐminimum pH values in stream waters are actually reported from the Finnish background catchments during snowmelt (de Caritat et al., 1996a), a fact that can be explained by lithological di€erences and thus a lower bu€ering capacity of the soils developed on lithologies resistant to weathering (e.g., quartzites) in northern Finland. In summary, the pH of lakes is not simply a function of input of potentially acidifying species to the catchment; it is the result of an interplay between fallout of acidifying (and other) species, inorganic geochemical neutralising reactions, organic acid/anion hydrochemistry, catchment hydrology and (micro)biological processes occurring within the lakes. The components of this interplay are not independent of each other and feedback mechanisms (positive and negative) exist between the various factors. Some elements (e.g., Al (Fig. 6), Mn and Zn) show steadily increasing concentrations in lake water from north to south. This is most likely due to increased mineral weathering rates and thus release of elements to water. Another explanation could again be that the observed e€ect is due to the large di€erences in vegetation zones and total biomass production from north to south. Climate would then appear to be an important factor determining elemental concentrations in lake water. K shows a peak near Monchegorsk. This could

1. that an unusual geology (gabbros and amphibolites) in the vicinity of Monchegorsk promotes well-buffered conditions in the soils and waters of the catchments feeding the high-pH lakes; 2. that reducing reactions (reduction of SO4 by monosulphides or organic C) in the lakes near Monchegorsk could consume protons and/or release hydrogen carbonate ions which bu€er the input of acidic species; 3. or, most likely, that the lakes in the immediate vicinity of the smelter might be in¯uenced by fallout of ash or other basic particulates (Moiseenko, 1994). While gaseous emissions from mineral processing works tend to be enriched in volatile gaseous phases which release acid on hydrolysis (e.g. SO2, CO2), ¯y ash phases are enriched in semi volatiles and basic oxides, yielding a high pH on hydrolysis. In W European plants, ¯y and bottom ashes are normally trapped eciently and disposed of in land®lls or in commercial products (Lee and Spears, 1998). The Kola smelters, however, have very ineffective control of particulate emissions. If released, potentially basic ash phases would be likely to fall out nearer the smelter than the potentially acidic gaseous phases, and might result in a rise of the pH in the lakes in the immediate vicinity of the smelters. In e€ect, a spatial fractionation of alkaline particulate phases and acidic gaseous phases may be occurring. A comparison of pH measurements from several

Table 2 pH of precipitation (rain and snow), stream water, lakes and soils from 8 catchments in or near the survey area (location see Fig. 1) pH-values medium raina snowb stream waterc

med. med. med. min. lake water ± closeste humusd med. med. C-horizond a

Russia

Finland

C1 Zapoljarnij

C2 Monchegorsk

C3 Kirovsk

C4 20 km S Monchegorsk

C5 Skjellbekken

C6 Kirakka

C7 Naruska

C8 Pallas

4.7 5 6.8 6 6.8 4.6 5.6

4 4.6 7 5.8 6.5 4.2 5.9

5 4.7 6.9 6.6 6.5 4.7 5.9

4.5 4.5 6.8 6.4 6.5 4.4 6.1

4.6 4.7 7.2 6.7 4.4 6

4.7 4.8 6.5 4.6 4 6.1

4.7 4.6 6.7 6.4 4.4 5.9

4.8 4.5 6.8 4.4 4.5 6

Reimann et al., 1997c. de Caritat et al., 1998a. c de Caritat et al., 1996a. d Kashulina et al., 1998. Humus and C-horizon: pH in water extraction. e Lakes: this study, pH in closest lake. b

Norway

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799

either be caused by increasing amounts of K being leached out of the soil due to vegetation damage near the smelter (Niskavaara et al., 1997) or by e‚uents/dust from the mining and processing of alkaline rocks near Apatity. Similar pro®les through Nikel/Zapoljarnij in an eastwest direction (Fig. 7) show the massive input of Ca from the huge open pit mining operations of basic rocks here. Anthropogenic input of Ca has been observed by Reimann et al. (1996b) in snow samples as well. Snow showed the highest pH values near the industrial operations and led these authors to speculations about what would happen to the accumulated load of heavy metals in the soils if this input ceases after shut down of the industrial operations. The pH of the lake waters is directly in¯uenced by emissions of basic mineral particles, the pH pro®le shows some similarity to the Ca pro®le (Fig. 7). At present, the S concentrations do not in¯uence the lake pH at all. Nickel and Cu concentrations show a steep gradient with distance to industryÐbackground values near Nikel/Zapoljarnij are reached within less than 100 km from sourceÐjust as shown above in north south direction for Monchegorsk. Aluminium shows the rather local impact of increased dust levels near industry, Na is only in¯uenced by the input of sea spray (note the peak at Murmansk fjord) and the pro®le mainly re¯ects the higher number of samples near the Barents Sea coast towards the east.

¯ux in the process). One should thus not attempt to calculate the `non marine SO4' component. The diagrams in Fig. 8 indicate the existence of an alkalinity (presumably HCOÿ 3 )-dominated group of waters dominantly in the south of the project area. These are assumed to be largely uncontaminated waters with a chemical signature dominated by geological weathering reactions, the hydrogen carbonate being derived from carbon-dioxide weathering of carbonates and silicates. Fig. 8 also indicates a signi®cant non-marine Na excess (Na signi®cantly exceeds Cl on a meq/l basis) in these waters, presumably derived from weathering of Nafeldspars. Sodium is a major cation in these waters, often exceeding Ca. When plotting SO4 against Ni, Na, Alkc and pH (Fig. 9) only the samples from the SOˆ 4 -group show a clear positive correlation of SOˆ 4 with the other parˆ ameters. In the pH-SOˆ 4 and alkalinity-SO4 diagrams one can see that the lakes are very well bu€ered (by either natural or arti®cial bu€ering agents)Ðthe samples with the highest SOˆ 4 -concentrations tend to show the highest pH and increased alkalinity. Thus the high input of presumably `acidifying' species near industry does not result in lake water acidi®cation but rather in a SO4 enrichment without any direct negative e€ect on the lake water pH.

3.3. XY- and ternary diagrams

Lake water composition in the survey area can be viewed as an interplay between 3 main factors: (1) in¯ow of groundwater or inter¯ow with a geological signature (Ca/Na±HCO3), derived from natural mineral weathering reactions. From an examination of regional element distribution maps, a selection of which are shown in Figs. 3±5, it appears that the distribution of the following elements is dominantly in¯uenced by geological sources: Ca, Mg, Na, K, Fe, Si, Al, Ba, Co, Cr, Li, Mn, Rb, Sr, U, V and Zn; (2) pollutionÐa strong in¯uence of anthropogenic sources is visible for: Ni, Cu, S, As, B (Monchegorsk only), Cd, Co, Mo (Apatity only), Sb, Ca (Nikel only), Na (Monchegorsk only) and (3) marine aerosols/dry fallout (Clÿ, Na, B, Brÿ). For some elements, where one would expect a sea spray signature (Mg, S, Sr) the other sources are so dominant, that this input is poorly visible in the regional maps. Some elements show increasing concentrations from north to south along a pro®le through the survey area. This feature is most prominent for Al, Mn, Rb, Sr and Zn. It can best be explained as being in¯uenced by climate/vegetation zones and/or increased mineral weathering rates towards the south. The `background' pH value increases as well from north to southÐa feature that cannot be explained by decreasing input of `acid

Fig. 8 shows the major anionic and cationic compoÿ sition of the lake waters. In the alkalinity±SOˆ 4 ±Cl ternary diagram the samples have been assigned to 3 major groups, depending on their anionic composition: a Clÿ-enriched group (®lled circles), an alkalinity group (open squares) and a SO= 4 enriched group (®lled triangles) and 3 intermediate groups. When mapping the location of these groups (Fig. 8) it becomes clear, that the samples in the Clÿ-group all occur along the coast, the SOˆ 4 ±group samples cluster near industry and settlements in the area while the alkalinity group occurs near Apatity/Kirovsk and at the southern project border. In the Mg±(Na+K)±Ca±ternary diagram (Fig. 8) the samples all plot roughly parallel to the Ca± (Na+K)±line, with the SOˆ 4 ±group of samples covering the whole range of compositions. In the Na/Clÿdiagram (Fig. 8) the samples from the `SOˆ 4 -group' mostly lie near the sea water ratio which is so clearly visible for the coastal samples. This may be partly due to the fact that Nikel and Zapoljarnij are located near the coast of the Barents Sea but also demonstrates that both Na and Clÿ are released by the smelters in a ratio similar to that of sea water (salt is added as a

4. Conclusions

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Fig. 7. E±W pro®les (with smoothed trend lines) through Nikel/Zapoljarnij for Ca, Cu, Ni, S, pH, Na and Al. Nikel is taken as the "0"-point, positive distances run towards the east. The locations of Nikel, Zapoljarnij and Murmansk are marked in the index map.

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801

Fig. 8. Ternary diagrams of the major anionic (as meq/l) and cationic (as mg/l) lake water composition, a map showing the loÿ ÿ cation of the subgroups de®ned using the alk±SOˆ 4 ±Cl diagram and a XY diagram of Na vs. Cl showing the in¯uence of sea spray vs. mineral weathering on lake water composition.

rain' (from long range atmospheric transport of air pollutants) from S to N, but may rather be due to a displacement of H+-ions from the soils near coast because of the massive input of sea salts (e.g., Na+) or may even be caused by vegetational e€ects (di€erent organic species released in the three vegetation zones crossed from N to S). Generally, the pH values measured in the lakes are surprisingly close to a neutral pH (median pH=6.6) and do not provide evidence for large scale acidi®cation by industrial pollution. Anthropogenic SO4 enrichment of lake waters has, however, occurred, implying the existence of an e€ective acid neutralising system in the catchments. Some lakes near industry have, in fact, elevated alkalinity and pH. Generally the direct in¯uence of industrial emissions on lake water chemistry appears to be rather local (some tens of km). The regional distribution of trace elements in the lake waters ®ts well with the results of mass balance calculations matching emission and deposition data by de Caritat et al. (1997b). These authors calculated that the major part of metal emissions is deposited in a limited area around the smelters and is thus not available for long range atmospheric

transport. Of all media sampled during the Kola project, lake water seems to be the least in¯uenced by the industrial emissions. When discussing environmental impact, it must be noted, however, that values presented here re¯ect summer conditions. A pronounced surge of heavy metals to the lakes near industry can be expected at snow melt (de Caritat et al., 1996b; Niskavaara et al., 1997). Such a seasonal surge could be sucient to cause severe environmental degradation, without a more permanent e€ect on lake water chemistry being observed. Sudden changes in water chemistry during snow melt are the largest threat to the aquatic ecosystem in the Arctic. de Caritat et al. (1996b) describe very signi®cant Ni and Cu concentration peaks in stream water collected near the smelters during this time while changes in pH are actually more pronounced in background areas and appear to be most in¯uenced by the nature of the soil substrate in any one catchment area, reacting with the melt water before it reaches the surface waters. The Sudbury case study (Keller and Gunn, 1995) suggests that today's environmental e€ects of the industrial pollution on the lakes could

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Fig. 9. XY-diagrams of some important parameters de®ning the lake water composition in the survey area. Subset de®nition (di€erent symbols) as in Fig. 8 (samples from the SOˆ 4 ±group are marked by a ®lled triangle).

C. Reimann et al. / Applied Geochemistry 14 (1999) 787±805

probably be reversed if the emissions were drastically cut. Acknowledgements Without the ®nancial support of the Royal Norwegian Ministry of the Environment, the Geological Surveys of Norway and Finland and Central Kola Expedition this project would not have been possible. We thank the whole Kola ®eld teams in Russia for ®eld sampling, the other participants in all three countries and O.M. Sñther of NGU for stimulating discussions. We would also like to thank our colleagues at the Norwegian Institute for Water Research (NIVA) A. Henriksen, B.L. SkjelkvaÊle and T. Traaen for interesting discussions and help with the selection of lakes for sampling.Mike Edmunds and JoÈrg Matschullat are thanked for their very constructive reviews of this paper. References AÈyraÈs, M., de Caritat, P., Chekushin, V.A., Niskavaara, H., Reimann, C., 1995. Ecogeochemical investigation, Kola Peninsula: sulphur and trace element content in snow. Water, Air and Soil Pollution 85, 749±754. AÈyraÈs, M., Reimann, C., 1995. Ecogeochemistry KolaÐField Manual. NGU Rapport nr. 95.111., 33 pp. AÈyraÈs, M., Pavlov, V., Reimann, C., 1997a. Comparison of sulphur and heavy metal contents and their regional distribution in humus and moss samples from the vicinity of Nikel and Zapoljarnij, Kola Peninsula, Russia. Water, Air and Soil Pollution 98, 361±380. AÈyraÈs, M., Niskavaara, H., Bogatyrev, I., Chekushin, V., Pavlov, V., de Caritat, P., Halleraker, J.H., Finne, T.E., Kashulina, G., Reimann, C., 1997b. Regional atmospheric deposition patterns of heavy metals (Co, Cr, Cu, Fe, Ni, Pb, V and Zn) and sulphur as seen in terrestrial moss samples from a 188 000 km2-area in northern Finland, Norway and Russia. J. Geochem. Explor. 58, 269±281. Banks, D., Frengstad, B., MidtgaÊrd, A.K., Krog, J.R., Strand, T., 1999. The chemistry of Norwegian groundwaters, I. The distribution of radon, major and minor elements in 1604 crystalline bedrock groundwaters. The Science of the Total Environment 222, 71±91. Boyd, R., Niskavaara, H., Kontas, E., Chekushin, V., Pavlov, V., Often, M., Reimann, C., 1997. Anthropogenic noblemetal enrichment of topsoil in the Monchegorsk area, Kola Peninsula, northwest Russia. J. Geochem. Explor. 58, 283±289. de Caritat, P., Reimann, C., AÈyraÈs, M., Niskavaara, H., Chekushin, V.A., Pavlov, V.A., 1996a. Stream water geochemistry from selected catchments on the Kola Peninsula (NW Russia) and in neighbouring areas of Finland and Norway: 1. Element levels and sources. Aquat. Geochem. 2, 149±168. de Caritat, P., Reimann, C., AÈyraÈs, M., Niskavaara, H.,

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