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Atmospheric Environment 89 (2014) 672e682

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Atmospheric Environment

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Snow and rain chemistry around the “Severonikel” industrial complex,NW Russia: Current status and retrospective analysis

Galina Kashulina a,*, Patrice de Caritat b, Clemens Reimann c

a Polar Alpine Botanical Garden-Institute, Kola Science Centre of RAS, Fersman St 18a, Apatity 184209, RussiabResearch School of Earth Sciences, The Australian National University, Canberra ACT 0200, AustraliacGeological Survey of Norway, PO Box 6315, Sluppen, N-7491 Trondheim, Norway

h i g h l i g h t s

� Current contamination level of rain and snow were studied around the Severonikel.� Ni and Cu concentrations in snow at present remain extremely high near the source.� Rain showed 5 fold decrease in Ni and Cu concentrations at present compared to 1994.� Height of sampling above ground was the reason of differences between rain and snow.� There are significant vertical differentiation of metals loads within ecosystem.

a r t i c l e i n f o

Article history:Received 12 May 2013Received in revised form27 February 2014Accepted 4 March 2014

Keywords:PrecipitationAcidityCopper (Cu)Nickel (Ni)Kola Peninsula

* Corresponding author.E-mail address: galina.kashulina@gmail.com (G. K

http://dx.doi.org/10.1016/j.atmosenv.2014.03.0081352-2310/� 2014 Elsevier Ltd. All rights reserved.

a b s t r a c t

The current (2005e2011) status of the chemical composition of snow cover and rain collected at a heightof 1.5 m above ground was studied within 11 km around the Severonikel industrial complex, one of thelargest SO2 and metal contamination sources in N Europe. In spite of a significant decrease in emissionsduring the past 20 years, Ni and Cu concentrations in snow remain extremely high near the source (2500and 1500 times background values, respectively). Although showing a five- to six-fold decrease in Ni andCu concentrations since 1994, rain water currently still has concentrations 150 and 80 times background,respectively. Differences in the chemical composition of snow pack and rain collected at a height of 1.5 mabove ground in this case are not caused by seasonal effects, but rather by the height of precipitationsampling relative to the ground.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

The Severonikel copperenickel industrial complex (Fig. 1) inMonchegorsk on the Kola Peninsula, NW Russia (one of the largestSO2 and heavy metal emitters in N Europe; Arctic Pollution Issues,1997; AMAP Assessment, 2006) has seen a significant decrease inits emissions during the last two decades (Fig. 2), following the1979 Convention on Long-Range Transboundary Air Pollution(UNECE, 1996). This paper presents the results of a study of thecurrent (2005e2011) chemical composition of atmospheric pre-cipitation in the local zone (1e11 km) around Severonikel carriedout as a part of a comprehensive environmental monitoring pro-gram (Kashulina and Saltan, 2008; Kashulina et al., 2010). Themajor aims of the paper are: (1) to characterize the current

ashulina).

chemical compositions of both snow cover on the ground and raincollected at the height of 1.5 m above ground; (2) to analyze theirspatial and temporal variability; (3) to document the precipitationchemistry response to decreased emission levels by comparing2005e2011 to our 1994 data sets (Reimann et al., 1997; Caritatet al., 1998); and (4) to discover the reason(s) for the funda-mental differences between the chemical composition of the snowand rain.

2. Methods

2.1. Study area

The study area is located in the central part of the KolaPeninsula, NW Russia (Fig. 1). Relief is complex with low moun-tains (Monche massif) adjoining hills and a large lake (LakeMonche). According to data from the Monchegorsk meteorological

Fig. 1. Location of study area showing monitoring plots (II-1eV-4), rain stations (II-ReV-R), Severonikel industrial complex, and Monchegorsk meteorological station with, inset, itswind rose diagram (with annual directional percentages).

G. Kashulina et al. / Atmospheric Environment 89 (2014) 672e682 673

station (Fig. 1), winters lasted from 150 to 180 days during 2005e2011 and average temperatures ranged between 12.5 and 16.1 �Cin July and between �15.2 and �6.6 �C in January (http://www.rp5.ru). Prevailing winds were from the S during winter andfrom the N and NW during summer. Median daily precipitationamounts at the studied plots during investigation period were0.8 L m�2 for winter and 1.6 L m�2 for summer. Northern taigavegetation is seriously damaged in the local zone due to theprolonged impact of the emissions in the area, leaving a techno-genic barren ground surface (Tikkanen and Niemela, 1995;Kashulina et al., 1997).

2.2. Contamination source

The Severonikel copperenickel industrial complex consists ofmany sections (refining, nickel electrolysis, metallurgical works,ash-heaps etc.) and has numerous sources of metals. For the pre-sent paper we distinguish two pathways of metals: (1) contami-nation originating from low-lying sources (numerous windows,doors, ventilation exhausts, ore and concentrate handling andtransport); and (2) contamination emanating from high-levelsources (four smokestacks 110e200 m high). The partial recon-struction and reorganization of the industrial complex (e.g.,

Fig. 2. Official SO2, Ni and Cu emission data for 1968e2011 for the Severonikel industrial complex (1968e1990 e compilation from various published sources, from 1990e2011 e

official departmental data e http://www.kolagmk.ru).

G. Kashulina et al. / Atmospheric Environment 89 (2014) 672e682674

initiation of sulfuric acid production, closure of the smelting sec-tion, use of Ni concentrate and NiS matte instead of ore as the rawmaterial for production and some other improvements, see http://www.kolagmk.ru) has resulted in a significant decrease in SO2, Niand Cu emissions during the last 20 years (Fig. 2). Emission of otherelements is not reported officially. However, detailed eco-geochemical investigations in the early 1990s (Reimann et al., 1998)and in 2000e2001 (Salminen et al., 2004) showed that Severonikelis also a source of a wide spectrum of other elements: Ag, Al, As, Ca,Cd, Co, Cr, Fe, Hg, Mg, Mn, Pb, Sb, Sr, Th, Tl, V, Zn and others.

2.3. Monitoring plots

The location and general characteristics of the monitoring plotsare shown in Fig. 1 and detailed in Table 1. Monitoring plots in thisstudy were established in five small catchments (Roman numbersIeV) 10e30 km2 in size (Table 1). Individual plots were located indifferent landscape positions (top of hill, hill/mountain slope, footof hill, local depression) within each catchment. Three to four in-dividual plots (Arabic numbers 1e4, starting from the upper most

Table 1Location relatively to source of contamination and the main characteristics of the monit

Catchment Plot Distance fromsource, km

Directionfrom source

Altitude, m Landsca

II II-1 7.9 N 158 Top of hII-2 7.7 N 145 Foot ofII-3 7.6 N 136 Local de

IIA IIA-1 11.5 N 155 Top of hIIA-2 11.5 N 149 Foot of

IIA-3 11.3 N 146 Local deIII III-2 7.6 NNW 157 Middle

III-3 7.8 NNW 142 River baIII-4 7.8 NNW 142 Local de

IV IV-1 3.2 NNW 178 Top of hIV-2 3.3 NNW 154 Low paIV-3 3.4 NNW 128 Local de

V V-2 3 E 230 MiddleV-3 2.5 E 176 Low paV-4 2 E 144 Local de

Meteorological station 4 NE 150 Top of h

position in the landscape) in each catchment create conjugatedgeochemical profiles or catenas. Due to the large size of catchmentII, two geochemical profiles (II and IIA) were established here. Thispaper represents data from 15 plots located within 11 km fromSeveronikel. Atmospheric precipitation sampling was carried outalso at the meteorological station in Monchegorsk (Fig. 1).

2.4. Sampling

Snow pack sampling was carried out at each monitoring plot atthe end of winter (end March to early April) between 2005 and2011. Ten to 30 individual snow pack subsamples were collected inopen areas (away from trees, tracks, etc.) with a clear Plexiglascoring tube and combined into one composite sample per plot. Carewas taken to avoid contact with the ground or ground vegetation atthe base of each snow core.

Each rain water sampler consisted of a 2 L polyethylene bottlewith a 10 cm diameter polyethylene funnel placed at the height of1.5 m above the ground surface using a wooden stake. Five rainstations (one in each catchment, except catchment IV, plus one at

oring plots.

pe Vegetation

Trees Dwarf shrubs

ill Sparse birch bushes Technogenic barrenthe slope Sparse birch bushes Rare dwarf shrubspression None Cotton grass bogill Young pines Rare dwarf shrubshill slope Rare young pines with birches

and willowsRare dwarf shrubs

pression None Cotton grass bogpart of hill slope Rare young pines Technogenic barrennk Rare young pines with birches Technogenic barrenpression None Cotton grass bogill Technogenic barren Technogenic barrenrt of hill slope Single pine, spruce and birch Technogenic barrenpression None Cotton grass bogpart of mountain slope Spruce with birch Bilberryrt of mountain slope Dense young birches Dwarf shrubspression None Cotton grass bogill None Dwarf shrubs

G. Kashulina et al. / Atmospheric Environment 89 (2014) 672e682 675

the Monchegorsk meteorological station), each consisting of fivesamplers placed 5 m apart, were established in an open area closeto the lowest monitoring plot in the landscape. A composite samplefrom the five samplers per rain station was collected three to fourtimes each summer between 2005 and 2011.

2.5. Analysis and quality control

The snow samples were melted in the laboratory at roomtemperature. For both rain and snow melt waters, pH wasmeasured in unfiltered samples. Aliquots of rain and snow meltwaters were filtered using 3e5 mm Blue Line filters (State standard12026-76). The filter residues (FR, representing the operationallydefined “particulate” form of elements) were dissolved withconcentrated nitric acid (HNO3) at 90 �C, and an aliquot of thefiltered waters (FW, representing the “soluble” form of elements)were acidified with hydrochloric acid (HCl) before being analyzedby Atomic Adsorption Spectrometry (AAS) for Cd, Co, Cu, Mn, Ni, Pb,Zn and Cr. In some samples the FR amount was insufficient fordissolution (<10 mg/L). In this case, element concentration in FRwas assumed to be nil. An unacidified aliquot of filtered waters wasanalyzed for SO4

2� by gravimetric method, and for Ca2þ, Mg2þ (with0.01 N Trilon� B chelating agent), Kþ and Naþ by Atomic EmissionSpectroscopy (AES).

All precipitation analysis was performed in the ISO Guide 25certified laboratory of the Kola Geological Laboratory-InformationCentre (Apatity, Russia). The same equipment and certifiedmethods of analysis were used throughout the project. Qualitycontrol procedures for the project consisted of analyzing duplicatesand State Standard Samples (Russia) in every batch. Accuracy andprecision of snow melt water and rain water analyses were withincertified ranges for all methods used.

Data analysis consisted primarily of performing non-parametricstatistics, and preparing time-series and Cumulative FrequencyDistribution (CFD) diagrams; these methods do not rely on partic-ular assumptions about the data structure or distribution. For dataanalysis all values below the DL were replaced by ½ DL. Temporaland spatial variation was estimated by max/min ratios for thecorresponding data sets.

For the retrospective analysis the current data (2005e2011; thisstudy) was compared with the 1994 study of the chemicalcomposition of snow cover (Caritat et al., 1998) and summerprecipitation (Reimann et al., 1997) in a small catchment located at

Table 2Median and minemax range values of acidity status parameters in the rain collected at tSeveronikel (Monchegorsk) industrial complex at present (2005e2011) and in the year o

Media pH SO42� Ca2þ

Rain, h ¼ 1.5 m Local zone, 2005e2011 (n ¼ 115)4.97 3.29 0.44.02e7.51 0.82e9.5 0.1e1.8

Rain, h ¼ 1 m Local zone (5e10 km S of source), 1994 (n ¼ 17) (Reim4.0 5.0 0.13.7e4.3 2.7e18.2 0.05e0.2

Rain, h ¼ 1.5 m Background e N Finland, 1994 (n ¼ 27) (Reimann et al.4.75 0.8 0.084.3e6.0 0.2e1.7 0.02e0.2

Snow cover Local zone, 2005e2011 (n [ 112)5.14 2.47 1.14.02e6.46 0.41e16 0.4e4.6

Snow cover Local zone (5e10 km S of source), 1994 (n ¼ 10) (Carita4.6 2.48 0.194.38e4.83 1.6e4.95 0.15e0.3

Snow cover Background e N Finland, 1994 (n ¼ 20) (Caritat et al., 14.6 0.73 <0.054.0e5.0 0.6e0.98 <0.05e0

5e10 km to the S of Severonikel. Results from these studies, rep-resenting two remote Finnish catchments, c. 200 km from Mon-chegorsk, are also used as representing the uncontaminatedbackground concentrations for snow and rain in the area in thefollowing.

3. Results and discussion

3.1. Precipitation acidity and SO42�

Although SO2 is the main component of emissions from Sever-onikel, precipitation acidification was not a serious problem in theregion even during the 1980e90s due to low gaseous SO2 reactivityand base cations co-emission (Kashulina et al., 2003). Current(2005e2011) SO4

2� concentration of rain water in the local zone isonly 4 times above background, and the concentration of basecations similarly is 4e6 times background (medians) (Table 2).Current SO4

2� concentration in snow melt water is 3.4 times abovebackground, while base cations 10 andmore times. pH of about 40%of the snowmelt water samples and most (76%) rainwater samplesin 2005e2011 varies within the background range. In the remain-ing 60% of snow melt water samples and in 18% of rain samples itwas even above the highest values found in the background area.Only in 6% of the rain water samples was pH lower than the lowestbackground value. Thus, the overall effect of the Severonikelemission at present is to lower (rather than exacerbate) atmo-spheric precipitation acidity in the local zone, especially in snow.

3.2. Other contaminants

Fig. 3 shows CFD diagrams of the “total” (FR þ FW) elementconcentrations in the snowmelt and rainwater from the local zonearound Severonikel during 2005e2011. Median and range values ofthe element concentrations in the snow melt and rain water arepresented in Table 3.

Median Ni concentration in snow melt water at present is 2500times above the median background value, Cu 1500 times. Themaximum Ni concentration in the snow melt water from the localzone is 20,000 times the maximum background value. One of theimportant features of the snow cover contamination at present isits Ni enrichment relative to Cu: the Ni/Cu ratio of 90% of thesamples is above 0.8, the value characterizing present-day emis-sions. Associated metal (Cr, Mn, Pb, Zn) levels in the snow melt

he height of 1.5 m above ground and snow melt water in the local zone around thef 1994 as well as in the background area of Northern Finland.

Mg2þ Naþ Kþ

0.12 0.39 0.290.06e0.73 0.07e1.71 0.02e1.93

ann et al., 1997)0.04 0.3 0.1<0.01e0.1 <0.1e0.72 0.02e0.36

, 1997)0.02 <0.1 0.07

6 <0.01e0.34 <0.1e0.19 0.02e0.26

0.24 1.11 0.220.12e1.33 0.22e24.5 0.03e2.16

t et al., 1998)0.1 0.5 0.08<0.05e0.13 0.2e0.7 0.06e0.13

998)All < 0.05 0.02 0.025

.17 0.01e0.02 0.02e0.05

Fig. 3. Cumulative frequency distribution diagrams of the total (FR þ FW) elementsconcentrations in the snow melt water and the rain at the height 1.5 m in the localzone around Severonikel industrial complex, 2005e2011.

G. Kashulina et al. / Atmospheric Environment 89 (2014) 672e682676

water are much lower. The level of snow contamination by As, Coand Cd could not be estimated because of DL problems in thebackground area. Still, it is evident that their concentrations in thesnow of the local zone at present exceed background levels a few10s or 100s of times.

As we have data only for the dissolved form of elements in rainwater (FW) from the background area (Reimann et al., 1997), wecould estimate its present-day degree of contamination in the localzone just for this form of elements. Median dissolved Ni, Cu and Co

Table 3Median and minemax range element total (FW þ FR) or dissolved (FW) concentrations (above ground in the local zone around the Severonikel (Monchegorsk) industrial complexFinland.

Media Form Ni Cu Co Pb C

Local zone, 2005e2011 (n ¼ 112, for As e 80, Cd e 96, Cr e 48)Snow cover FW þ FR 702 525 18.3 8.6 0

89e9093 112e6024 2.2e438 <1e66 <

Local zone, (5e10 km S of source), 1994 (n ¼ 15) (Caritat et al., 1998)Snow cover FW þ FR 846 657 82.4 9.2 0

602e2897 417e2616 40e149 6.7e22 0Background e N Finland, 1994 (n ¼ 20) (Caritat et al., 1998)Snow cover FW þ FR 0.27 0.32 All <0.05 0.84 A

0.17e0.42 0.18e1.1 0.62e1.2Local zone, 2005e2011, h ¼ 1.5 m (n ¼ 115)Rain FW 19 40 1 2 <

<1e216 <1e223 <1e6 <1e89 <

Rain FW þ FR 32.3 61.8 1.36 2.34 0<1e603 <1e434 <1e16.6 <1e89 <

Local zone (5e10 km S of source), 1994, h ¼ 1 m (n ¼ 17) (Reimann et al., 1997)Rain FW 57 231 11.8 6.34 0

24e132 86e848 2.2e69 2.1e40 0Background e N Finland, 1994, h ¼ 1.5 m (n ¼ 27) (Reimann et al., 1997)Rain FW 0.13 0.5 All <0.02 0.64 <

<0.06e0.49 0.2e2.1 0.1e2.2 <

a 1/2 DL values are used for the calculations.

concentrations in the rain within the local zone at present exceedbackground by 146, 80 and >50 times, respectively. The Ni/Cu ratioin most (80%) of the rain water samples was <0.8.

Dissolved Pb and Mn concentrations are only two to three timeshigher than background. Levels of rain contamination by As, Cd andCr (based on median values) could not be estimated because of DLproblems. Maximum Pb, As, Zn and Mn concentrations in the localzone exceed maximum background values by >20 times, and up to100s of times for Cr.

3.3. Element forms in precipitation

During the melting of snow in the laboratory and the long pe-riods between rain water sampling, the particulate (FR) part ofprecipitation (dust) had the potential to partially dissolve. Still ourdata show that particulate deposition is high (Table 4).

The highest proportion of particulate precipitation in snow meltwaterwas found for Cr and Co: in 80% of the snowmelt samples theparticulate form of these elements represented more than half oftheir total concentration. The proportion of particulate Ni is higherthan its dissolved form in 70% of the samples. The percentage ofsamples with predominance of particulate and dissolved forms isapproximately equal for Mn and Pb. The dissolved form pre-dominates for Cd (in 93% of samples), As (85%), Cu (75%) and Zn(70%).

For summer atmospheric precipitation the percentage of samplesin which the particulate form predominates is: 45% of samples forNi, 35% for Mn, 30% for Cu, 17% for Co, 15% for Cr and 9% for Pb.

3.4. Dust in precipitation

Both the quantity and the chemical composition of dust beingdeposited with atmospheric precipitation are characteristic of thetechnogenic load on ecosystems. Dust concentration estimatedfrom the FR results was <1 mg L�1 in 8% of the snow melt watersamples from the local zone, 1e10 mg L�1 in 16%, 10e100 mg L�1 in60%, 100e1000 mg L�1 in 16% of them. Maximum dust content insnow melt water (plot IV-1 in 2011) was 820 mg L�1.

Extremely high Ni concentrations in the filter residues (FR) ofmany samples (median 1.8%, maximum 10%; see Table 5, Fig. 7)

mg L�1) in the snow melt water and in the rain water sampled at the height of 1.5 mat present (2005e2011) and in 1994, as well as in the background area of Northern

d As Zn Mn Cr Ni/Cu

.18 2.2 46.7 15.9 3.4 1.30.05e1.5 <1e16.4 4.6e707 <1e287 <1e266 0.3e3.9

.44 5.6 17.6 8.48 6.71 1.1

.3e1.1 4.3e17.7 14.5e34 5.6e34 4.5e21 0.72e5

ll < 0.03 All < 0.1 3.7 0.63 0.25a 0.82.5e27 0.43e4.0 0.19e0.8 0.22e1.8

0.05 <1 4 4 <1 0.480.05e0.5 <0.5e6 <1e350 <1e80 <0.5e58 0.1e2.3.07 4.01 14.5 7.97 2.00 0.590.05e0.7 <0.5e6.0 <1e354 <1e80 <0.5e58 0.06e1.45

.89 12.3 55.5 1.99 0.47 0.30

.32e5.1 3.6e84 32e197 1e4.4 0.25e0.95 0.13e0.46

0.02 0.07 9.2 2.4 All <0.2 0.270.02e0.64 <0.05e0.18 2.5e14 0.45e11 0.03e1.2

Table 4Median and minemax range of particulate (FR) form proportion (%) of total(FW þ FR) element concentrations in snowmelt water and in rain at height of 1.5 mabove ground in the local zone around the Severonikel (Monchegorsk) industrialcomplex in 2005e2011.

Media Ni Cu Co Pb Cd As Zn Mn Cr

Snow cover 57 39 67 44 15 18 24 48 670e89 0e86 0e98 0e96 0e88 0e93 0e94 0e99 0e100

Rain,h ¼ 1.5 m

43 36 12 8 15 5.5 37 34 170e98 0e92 0e81 0e66 0e68 0e25 0e95 0e94 0e97

G. Kashulina et al. / Atmospheric Environment 89 (2014) 672e682 677

imply that theymust consist entirely of Ni ore (concentrations from0.24 to 4.2%, http://www.nornik.ru) particles and/or contain aconsiderable proportion of Ni concentrate or Ni matte (concentra-tions up to 45%) particles. The Cu content in the dust of themajorityof snow melt water samples (median 1.0%, maximum 6.7%) atpresent is on par with ore concentrations too (from 0.36 to 5.8%).The concentration of associated contaminants (As, Cd, Cr, Mn, Pband Zn) in the FR is also very high.

Dust concentration in summer atmospheric precipitation was<1 mg L�1 in 5% of samples, 1e10 mg L�1 in 30%, 10e100 mg L�1 in50%, and >100 mg L�1 in 15% of them. These estimates are a littlelower in comparison to the snow, partly because rain was notsampled in the most contaminated catchment (IV).

Ni, Cu and Co concentrations are considerably lower in summerdust (Table 5, Fig. 7) than in winter dust, especially for Ni and Co.This contrast is less considerable for the associated elements (Pb,Cd, As, Zn, Mn and Cr).

3.5. Spatial variation and distribution

Atmospheric processes responsible for the airborne transport ofcontaminants are very dynamic (e.g., Brimblecombe, 1996).Therefore the monitoring plots differ significantly in elementconcentrations in snow, in spite of the relatively small size of thestudy area. The differences in SO4

2� concentrations in snow meltwater betweenmonitoring plots (Fig. 4) vary from 3 fold (2006) to 8fold (2011). Differences in the concentrations of other elements insnow melt water between plots vary from 4 (Mn in 2008) to morethan 500 fold (e.g., Mn and Cr in 2010). The most uneven distri-bution in space is characteristic of dust: the differences in dustconcentration in snow melt water between plots varied from 9(2008) to several 1000s fold (2010).

The high instability in the spatial distribution of contaminants isconfirmed by the fact that their maximum and minimum concen-trations in snow melt water occurred on different plots in differentyears. Most frequently, however, the maximum concentrations ofthe main contaminants SO4

2�, Ni, Cu, Co and dust were recorded inthe plots located nearer to the source in a NNW (catchment IV) or N(catchment II) direction.

Table 5Median and minemax range of element concentrations (mg kg�1) in dust (FR) of snow cSeveronikel (Monchegorsk) industrial complex at present (2005e2011) and in 1994.

Media Ni Cu Co

Local zone, 2005e2011 (n ¼ 112, Cd e 96)Snow cover 17759 10220 568

646e99763 370e67003 28e2927Local zone, (5e10 km S of source), 1994 (n ¼ 15) (Caritat et al., 1998)Snow cover 2570 2710 111

776e6360 727e6440 32e242Local zone, 2005e2011, h ¼ 1.5 m (n ¼ 115)Rain, h ¼ 1.5 612 982 17.2

28e7834 68e9327 <0.1e215

The occurrence of the minimum concentrations of the maincontaminants in snow melt water is less stable. In different yearsand for different elements, the minimum concentrations occurredin the most remote plots in a NNW (catchment II), N (catchmentIIA), E (plots V-2, V-3) or NE (meteorological station) direction.

The distribution of the associated elements was individual toeach element and rarely coincided with the distribution of themajor contaminants.

Differences in element concentrations in summer precipitationbetween catchments (Fig. 5) were less significant (mainly from 1.5to 5 fold, rarely reaching 100 fold) than in snow. The distribution ofelement concentrations in rain water between catchments waseven less regular than in snow. For rain the maximum concentra-tion of the major contaminants could be found in any of the studiedcatchments, independent of direction or distance from source. Thesame was true for the minimum concentrations. The spatial dis-tribution of minimum and maximum concentrations was differentfor different elements. Even for the metals Ni and Cu, themaximumconcentrations occurred in the same catchments only 13 out of 22sampling events; for the minimum concentrations this onlyoccurred on 10 occasions.

The amount of dust in rain was one of the most variable com-ponents of emission. The differences between catchments excee-ded 10 fold in 6 out of 22 rain sampling events, reaching 300 fold forthe first sampling event of 2010. For the remaining 16 samplingevents, the difference was less than 10 fold.

3.6. Temporal variation and current dynamics

While most investigations in the area were based on a shortperiod of sampling (e.g., Jaffe et al., 1995; Lindroos et al., 1995) thepresent study is based on precipitation sampling over a 7 year-period (2005e2011). This gives us the opportunity to estimatetemporal precipitation chemistry variability. According to officialdata (Fig. 2), SO2, Ni and Cu emissions decreased by 23, 31 and 21%,respectively, during the years of observation (2005e2011). Con-centrations in snow melt water sampled in our plots over 7 yearsdiffered by a factor of 3.5e18 for SO4

2�, 2e6 for Ni and Cu, and 3e30or more for the associated elements (Pb, Cd, Mn, Zn). In contrast tothe reduction in emissions, which occurred gradually, the changesin the concentration of contaminants in snow melt water on thestudied plots were irregular over the years and were different foreach element and for each plot. Thus, even for the main metalsemitted, Ni and Cu, the occurrence of maximum concentrationsduring the same year coincided only in 8 of the 16 plots. At theremaining plots, maximum concentrations of Ni and Cu occurred indifferent years.

The minimum concentrations of the majority of the contami-nants onmost plots during 2009e2010were possibly caused by theloss of elements during the strong thaws (as shown by Johannessenand Henriksen (1978), up to 50e80% of contaminants are released

over and rain at height of 1.5 m above ground samples in the local zone around the

Pb Cd Mn Ni/Cu

130 0.95 268 1.84e2094 <0.1e52 57e2060 0.1e5.4

27 0.68 91 1.08e80 0.19e1.6 26e389 0.5e2.3

22.6 0.6 140 0.6<1e1352 <0.05e17 6.8e1485 0.1e3.2

Fig. 4. Sulfate (FW), total (FR þ FW) Ni and Mn concentrations in the snow melt water from the monitoring plots in the local zone around Severonikel industrial complex, 2005e2011.

G. Kashulina et al. / Atmospheric Environment 89 (2014) 672e682678

with the first 30% of melt water) that preceded or coincided withsampling. The following year (2011) the concentration of all con-taminants in snowmelt water in the local zone, with the exceptionof Zn, increased. For some plots, themaximum concentrations of Ni,Mn (Fig. 4), Cu and Co of all years of observation were reported in2011.

Differences in contaminant concentrations between individualrain water samples from the studied catchments were more sig-nificant (Fig. 5): about 10 fold for SO4

2�, 230e800 fold for Ni,17e300fold for Cu, 96e700 fold for Zn, 30e180 fold for Pb, and 16e160 foldfor Mn. Extremely high (e.g., samples from 8.08.2007 to 18.08.2011)or low (e.g., sample from 5.07.2011) amounts of precipitationlowered or increased, respectively, contaminant concentrations inrain.

Seasonally weight-averaged element concentrations in rainwater that fell on the studied catchments varied over the years by afactor of 2e4 for SO4

2�, 10e20 for Ni, and 4e8 for Cu (Fig. 6). Butthese also considerably exceeded the level of emissions reductionand, in contrast to this reduction, they were not regular or gradual.More significant reductions in Ni and Cu concentrations recordedduring the last two years were possibly also connected with pre-cipitation amounts and intensity: in July and August of 2010 and2011 the amount of precipitation was about 1.5 times higher thannormal.

The variation of weight-averaged concentrations of the associ-ated contaminants in rainwater over the years was about 10 fold forZn (for the majority of catchments), 3e13 fold for Mn (dependingon catchment), and 4.5e38 fold for Pb.

3.7. Differences between snow and rain compositions

As shown above the chemical compositions of snow and rain inthe local zone differ considerably. The median concentrations were

higher in snow melt water (median of all data set, except catch-ment IV, where no rain sampler was established) compared to rainwater (median of all data set) by a factor of 17 for Ni, 6.5 for Cu, 9 forCo, 2.4 for Pb, 2.1 for Cd, 3.8 for Zn, and 2 for Mn. The medians of Crconcentrations were about the same in both materials. The onlyelement displaying the opposite behavior was As, whose medianwas 1.7 times higher in rain than in snow.

What are the reasons for these fundamental differences be-tween the chemical composition of snowand rain in the local zone?The seasonal distribution of the wind direction alone could notexplain these differences, since wind blew from the emissionsource towards the sampled plots with similar frequency in winter(47%) and in summer (36%) during 2005e2011.

Differences in the ability of snow and rain towash contaminantsout of the atmosphere also fail to satisfactorily explain the con-trasting chemical compositions of the studied media. Indeed, re-sults of previous studies in the same area have shown that theconcentration of contaminants in rainwere, on the contrary, higherthan in the snow, when both media were sampled at the sameheight relative to the ground surface (Z. Jevtugina, personalcommunication; Vernigora, 2002). The sampling of snow cover andrain (at the height of 1 m above the surface) in 1994 also showedsignificant differences between these media: concentration (dis-solved form) in the snow cover was higher than in rain by a factor of4.6 for Ni, 2.4 for Cu, 2.8 for Co, 2.4 for Cr and 1.7 for Mn (Table 3).

Comparative analysis of the FR proved most informative forunderstanding the differences in the chemical composition of snowand rain. Extremely high Ni, Cu and Co concentrations in the dust ofsnow indicate that highly concentrated technogenic dust origi-nating from Ni production was the major source of the snow covercontamination. Since this material did not appear to the sameextent in summer dust collected at the height of 1.5 m, it is likelythat the source of dust in snow are the low-lying sources (handling

Fig. 5. Sulfate (FW), total (FR þ FW) Ni and Mn concentrations in individual rain samples at the height of 1.5 m from the studied catchments (IIeV) and Meteorological station (M/s)in the local zone around Severonikel industrial complex, 2005e2011.

G. Kashulina et al. / Atmospheric Environment 89 (2014) 672e682 679

and transport of Ni concentrate at the plant, dust from numerousdoor and window apertures and exhaust vents), from which tech-nogenic dust is dispersed by atmospheric flows in the local zonearound Severonikel only in the layer closest to the earth’s surface.Mineralogical analysis of dust from the snow and soil samplescollected within the local zone revealed ore particles, oxides andsulfides, as well as partially fused ore particles and metal alloys(Gregurek et al., 1999; Felfernig et al., 2000).

Comparative analysis of different natural materials showed thatneither the highly concentrated technogenic dust nor the erosion ofextremely contaminated soil did reach the height of 1.5m above theground surface (Fig. 7). The major source of contamination for thesummer dust (rain FR) could be only the filtered gas-dust emissionsfrom the high-level controlled sources at Severonikel e the 4 highsmokestacks nowadays equipped with efficient filters.

Thus, based on the present results it may be concluded that themajor reason for the marked differences in the chemical compo-sition of snow cover and summer precipitation in the local zonewas the different height of sampling of the two media relative tothe ground surface. This finding implies that the tree/canopy layerin the local zone experiences a much lower heavy metals load thanthe lower/ground vegetation (moss, lichen and dwarf shrub layer)and soil at present.

3.8. Retrospective analysis

Only summer precipitation responded to the 2.5 fold decrease inSO2 emissions since 1994: the 2005e2011 median of SO4

2� con-centration in the rain was 1.5 times lower than in 1994 (Table 2).Concentrations of SO4

2� in snowmelt water from the local zone didnot change within this period.

Recent (2005e2011) concentrations of base cations Ca and Mgin both snow and rain of local zone, on the contrary, increased incomparison with 1994. As a result, the pH of atmospheric precipi-tation within this period increased here, especially in the case ofsummer precipitation.

According to official data (Fig. 2), present-day emissions havebeen reduced by a factor of 3e4 for Ni, and 3 for Cu in comparisonto 1994. Within this period, median Ni and Cu concentrations insnow melt water decreased only by 20% (Table 3). At the sametime changes in the Ni/Cu ratio in snow melt water and in theemissions diverge. This indicates that changes in emissions since1994 were not only quantitative; over this time interval thecomposition of emissions changed considerably, a consequence ofthe significant change in technological processes implemented atthe Severonikel industrial complex. In particular, this enterprisenow uses Ni concentrate and matte (with Ni concentrations up to

Fig. 6. Weighted average SO4�2 (FW), total (FR þ FW) Ni, Cu and Pb concentrations in the rain at the height of 1.5 m from the studied catchments (IIeV) and Meteorological station

(M/s) in the local zone around Severonikel industrial complex, 2005e2011.

G. Kashulina et al. / Atmospheric Environment 89 (2014) 672e682680

45%) as the raw material for production, compared to NieCu ore in1994.

Changes in the composition of dust in the snow testify to anotable increase in the highly concentrated technogenic dust in theemissions from the low-lying sources. Metal concentrations insnow dust have increased considerably since 1994 (Table 5, Fig. 7):by a factor of 7 for Ni, 4 for Cu, 5 for Co, almost 10 for Zn, 5 for Pb,and about 3 for Mn and Cr. Cd concentrations increased insignifi-cantly (only 1.5 times), whilst As actually decreased. The two lastelements are more volatile, and are mostly lost from the ore duringNi concentrate production.

Whilst Ni, Cu and Co concentrations in the dust increased, dustquantity in the snow cover at present has been reduced since 1994almost 10 fold: the dust content in the snowmelt water in 1994was230 mg L�1, now it is only 25 mg L�1 (median values). Nonetheless,heavy metals loads on the low vegetation layer (mosses, lichens,dwarf shrubs) and soil within the local zone remain extremely highat present in spite of the significant decrease in official emissions.

With the retrospective analysis of the contamination levels ofsummer atmospheric precipitation it is necessary to remember thatnot only the position relative to source, but also relative to theground surface were different in the 1994 studies (Table 3).

Some improvements at the Severonikel complex (closing offoundry and reconstruction of metallurgical and refining sections)resulted in emission reductions from the high-level controlledsources (smokestacks). This led to a significant decrease in theconcentrations of contaminants in the rain water in the local zonein comparison to 1994 (Ni 3 fold, Cu 5 fold, Co 12 fold, Pb 3 fold, Zn10 fold). Thusmetal loads on the trees canopy level in the local zonedecreased significantly from 1994 to 2011.

4. Conclusions

1. Current (2005e2011) levels of SO42� concentration in snowmelt

water and in rain water were only 4 times higher near thesmelter in comparison to background; the concentrations of

basic cations (Ca and Mg) were 5e6 times above background.Therefore the current acidity of atmospheric precipitation waslower in the surroundings of the industrial emission sourcesthan in the background.

2. The current levels of Ni, Cu and Co concentrations in snowwithin the industry impacted zone remained extremely high,exceeding background values by a factor of 2500, 1500 and 400,respectively. The levels of Ni, Cu and Co concentrations in rainwater were considerably lower, exceeding background 146, 80or >50 fold, respectively.

3. Differences between the chemical composition of winter andsummer precipitation in the local zone were caused not byseasonal effects, but by height of sampling relative to the groundsurface. Highly concentrated technogenic dust from low-lyingsources (windows, doors, ventilation exhausts, ore andconcentrate transport), transported by surface atmosphericflows, was the major source of contaminants for the snow cover.The dominant source of rain contamination (at the height of1.5 m above ground) was filtered gas-dust emissions from high-level sources (smokestacks).

4. Winter and summer precipitation in the surroundings of in-dustry responded differently to the reduction in contaminantemissions since 1994. Nickel and Cu concentrations in snowmelt water remained practically unchanged since 1994. This wascaused by the combination of an increase in the concentration ofcontaminants in the emitted technogenic dust with a significantdecrease of its quantity. Reduction in emissions from thesmokestacks resulted in a significant decrease in the concen-tration of contaminants in rain.

5. Since atmospheric distribution of contaminants is a very dy-namic process, especially in a topographically complex region,high spatial and temporal variability in the concentration ofcontaminants was characteristic of atmospheric precipitation inthe local zone, despite the relativelysmall size of the studied area.

6. Variations in contaminant concentration and deposition on thestudied plots, both for snow and rain, were not regular in the

Fig. 7. Cumulative frequency distribution diagrams of the following parameters: Ni, Cu, Mn, Pb and Zn concentrations (mg kg�1) and Ni/Cu ratio in the filter residue of snowsamples in 2005e2011 (SnFR 05-11) and in 1994 (SnFR 94), of rain at the height 1.5 m in 2005e2011 (RFR 05-11), in the upper organic (OS 05-11) and mineral (MS 05-11) soilhorizons in the local zone around Severonikel industrial complex.

G. Kashulina et al. / Atmospheric Environment 89 (2014) 672e682 681

current dynamics and did not coincide with the dynamics of theofficial emission volumes. The temporal irregular variations inelement concentrations in atmospheric precipitation consider-ably exceeded the recent rates of emissions reduction.

7. The comparative analysis of the chemical composition of snowand rain at the height of 1.5 m revealed a significant verticaldifferentiation of metals loads on different layers of theecosystem near industry at present: the tree layer experiences amuch lower heavymetals load in comparison to the lower moss,lichen and dwarf shrub layer.

Acknowledgments

This study was carried out within the framework of the regionalprogram “Environment protection and hygiene andmaintenance ofecological safety in the Murmansk region” together with OSC “KolaGeological Laboratory-Information Centre” (Apatity, Russia). Theauthors wish to thank all participants for their assistance in thefield and in the laboratory.

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