Report of Investigation 196 - arkisto.gsf.fi - Geologian tutkimuskeskus

GEOLOGICAL SURVEY OF FINLAND 

Report of Investigation 196 

2012 

High pre-mining metal concentrations and conductivity in peat 

around the Talvivaara nickel deposit, eastern Finland 

Markku Mäkilä, Kirsti Loukola-Ruskeeniemi and Heikki Säävuori

GEOLOGIAN TUTKIMUSKESKUS GEOLOGICAL SURVEY OF FINLAND 

Tutkimusraportti 196 Report of Investigation 196 

Markku Mäkilä, Kirsti Loukola-Ruskeeniemi and Heikki Säävuori 

HIGH PRE-MINING METAL CONCENTRATIONS AND CONDUCTIVITY IN PEAT 

AROUND THE TALVIVAARA NICKEL DEPOSIT, EASTERN FINLAND 

Unless otherwise indicated, the figures have been prepared by the authors of the publication. 

Front cover: Study site M2 in the Talvivaara mine in 2011. The peat samples for the present study 

were selected in 2005 when the site was located in the middle of a forest, before the large-scale mining 

activities began. Photo: Markku Mäkilä, GTK. 

Layout: Elvi Turtiainen Oy 

Printing house: Vammalan Kirjapaino Oy 

Espoo 2012

Mäkilä, M., Loukola-Ruskeeniemi, K. & Säävuori, H. 2012. High pre-mining 

metal concentrations and conductivity in peat around the Talvivaara nickel 

deposit, eastern Finland. Geological Survey of Finland, Report of Investigation 

196, 36 pages, 31 figures and 7 tables. 

The Talvivaara Ni-Cu-Zn-Co deposit contains more than 1500 Mt of lowgrade 

ore, and has been mined since 2008 (0.22% Ni, 0.13% Cu, 0.49% Zn, 

0.02% Co). Three peat study sites representing different bedrock types and hydrological 

conditions were sampled in the Talvivaara area in 2005, before the 

large-scale mining activities began. The chemical and physical properties of 

peat were studied from 58 samples. The chemical concentrations of peat were 

affected by factors such as the capillary transport of water through the underlying 

sandy till, plant physiology and geochemical processes in peat. The concentrations 

of Co, Cu, Fe, Mn, Ni, U, Zn and S and conductivity were lower 

at the study site on mica schist bedrock than in peat at the two study sites underlain 

by so-called black schists (metasedimentary rocks rich in graphite and 

sulphides). These metals displayed greater concentrations in the bottom layers 

of Carex (sedge) peat than in the surface layer of Sphagnum (moss) -dominated 

peat. It seems likely that hydrological conditions at one sloping peatland site 

underlain by black schist have been conducive to production and transport of 

acidic surface waters with metal- rich suspension from adjacent Ni-rich black 

schist outcrops and glacial till throughout the entire history of peat accumulation. 

The peat layer evidently functioned in the same way as peat filters in 

the remediation of acid mine drainage in present-day mine environments, i.e. 

metals were retained in the peat. Ditches also locally reached the underlying 

Ni-rich bedrock and/or Ni-rich glacial till. At this black schist study site, pH 

values varied between 2.8–3.8 beneath the surface peat layer. These pH values 

are lower than can be tolerated by Carex peat-forming plants. The acidity of 

peat changed in the 1960s when the peat became drier due to drainage of the 

the peatland, and sulphur oxidized to SO 4 . We conclude that in sulphide-rich 

terrain, sulphur concentrations in peat can be high, and leaching of sulphur 

from peat to surface waters during and after peatland drainage activities may 

lead to environmental problems. The conductivity probe developed at the Geological 

Survey of Finland provides a cost-effective tool for locating sulphiderich 

peat formations. 

Keywords (GeoRef Thesaurus, AGI): peat, chemical properties, metals, sulfur, 

background level, electrical conductivity, mica schist, black schists, nickel, acid 

rock drainage, Talvivaara, Sotkamo, Finland 

Markku Mäkilä, Kirsti Loukola-Ruskeeniemi, Heikki Säävuori 

Geological Survey of Finland, P. O. Box 96, FI-02151 Espoo, Finland 

E-mail: markku.makila@gtk.fi, kirsti.loukola-ruskeeniemi@gtk.fi, heikki.saavuori@gtk.fi 

ISBN 978-952-217-194-8 (PDF) 

ISBN 978-952-217-195-5 (paperback) 

ISSN 0781-4240

Mäkilä, M., Loukola-Ruskeeniemi, K. & Säävuori, H. 2012. High pre-mining 

metal concentrations and conductivity in peat around the Talvivaara nickel 

deposit, eastern Finland. Geologian tutkimuskeskus, Tutkimusraportti 196, 36 

sivua, 31 kuvaa ja 7 taulukkoa. 

Talvivaaran Ni-Cu-Zn-Co -esiintymä sisältää yli 1500 Mt metallipitoisuudeltaan 

suhteellisen alhaista malmia, jota on louhittu vuodesta 2008 lähtien 

(0,22 % Ni, 0,13 % Cu, 0,49 % Zn, 0,02 % Co). Talvivaaran alueelta otettiin 

vuonna 2005 turvenäytteitä kolmelta suolta, jotka edustavat erilaisia kallioperäalueita 

ja hydrologisia olosuhteita. Turpeen kemiallisia ja fysikaalisia ominaisuuksia 

tutkittiin 58 näytteestä. Näytteiden kemialliseen koostumukseen 

ovat vaikuttaneet monet eri tekijät kuten veden kapillaarinen nousu suon pohjan 

hiekkamoreenissa ja turpeen kasvifysiologiset ja geokemialliset prosessit. 

Co, Cu, Fe, Mn, Ni, U, Zn ja S -pitoisuudet ja johtavuus olivat alemmat kiilleliuske-kallioperässä 

olevalla suolla kuin mustaliuskeen (grafiittia ja sulfideja sisältävien 

metasedimenttikivien) päällä olevilla soilla. Nämä metallit esiintyivät 

suurempina pitoisuuksina soiden pohjalla saraturpeissa kuin suon pinnan rahkaturpeissa. 

Mustaliuskealueella olevalla rinnesuolla hydrologiset olosuhteet 

edistivät happamien pintavesien muodostumista ja kulkeutumista turpeeseen 

viereisiltä runsaasti nikkeliä sisältäviltä mustaliuskekallioilta ja moreenikerroksista 

koko turpeen muodostumishistorian ajan. Ilmeisesti turvekerros toimi 

samalla tavalla kuin turvesuodattimet happaman kaivosvalunnan korjaamisessa 

nykypäivän kaivosympäristöissä, metalleja pidättyi turpeeseen. Mustaliuskealueella 

olevalla rinnesuolla pH-arvot vaihtelivat 2.8–3.8 välillä pintaturvekerroksen 

alla. Nämä pH-arvot ovat alempia kuin saraturvetta muodostavat 

kasvit kestävät. Turpeen happamuus muuttui 1960-luvulla, kun turvekerrokset 

kuivuivat ojituksen vuoksi ja rikkiä hapettui sulfaatiksi. Alueilla, joissa 

kallioperä ja/tai maaperä sisältävät paljon sulfideja, turpeen rikkipitoisuudet 

voivat olla korkeita. Rikin kulkeutuminen turpeesta pintavesiin turvemaiden 

ojituksen aikana ja sen jälkeen saattaa johtaa ympäristöongelmiin. Geologian 

tutkimuskeskuksessa kehitetty johtavuusluotain tarjoaa kustannustehokkaan 

menetelmän sulfidirikkaiden turvekerrosten paikantamiseen. 

Asiasanat (Geosanasto, GTK): turve, kemialliset ominaisuudet, metallit, rikki, 

taustapitoisuus, sähkönjohtokyky, kiilleliuske, mustaliuskeet, nikkeli, hapan 

valuma, Talvivaara, Sotkamo, Suomi 

Markku Mäkilä, Kirsti Loukola-Ruskeeniemi, Heikki Säävuori 

Geologian tutkimuskeskus, PL 96, 02151 Espoo 

S-posti: markku.makila@gtk.fi, kirsti.loukola-ruskeeniemi@gtk.fi, heikki.saavuori@gtk.fi

4 

CONTENTS 

1 INTRODUCTION ......................................................................................................................... 5 

2 STUDY AREA ............................................................................................................................... 6 

2.1 Bedrock ................................................................................................................................... 6 

2.2 Soil .......................................................................................................................................... 7 

2.3 Peatlands ................................................................................................................................. 7 

2.4 Airborne geophysics ................................................................................................................ 9 

3 MATERIALS AND METHODS .................................................................................................... 9 

3.1 Sampling .................................................................................................................................. 9 

3.2 Laboratory analyses ................................................................................................................10 

3.3 Electrical conductivity ............................................................................................................10 

4 RESULTS .......................................................................................................................................11 

4.1 Chemical concentrations and peat properties of study sites ...................................................11 

4.2 Correlation between peat properties .......................................................................................24 

5 APPLICATION OF ELECTRIC CONDUCTIVITY MEASUREMENTS IN 

ENVIRONMENTAL STUDIES ..................................................................................................32 

6 DISCUSSION ...............................................................................................................................32 

7 CONCLUSIONS ...........................................................................................................................34 

ACKNOWLEDGEMENTS ..............................................................................................................35 

REFERENCES .................................................................................................................................35

Geologian tutkimuskeskus, Tutkimusraportti 196 – Geological Survey of Finland, Report of Investigation 196, 2012 

High pre-mining metal concentrations and conductivity in peat around the Talvivaara nickel deposit, eastern Finland 

Sulphide ores and certain other rock types can influence 

elemental abundances in peat (e.g. Salmi 

1955, Kokkola & Penttilä 1976, Virtanen 1978, 

1990, 1993, 2004, 2005, Virtanen et al. 1997, Virtanen 

& Lerssi 2008). Black schists contain sulphides, 

weather more easily than other rock types 

and cause acid rock drainage and acidification of 

surface waters (Loukola-Ruskeeniemi et al. 1998, 

Gustavsson et al. 2012). The chemical composition 

of peat is affected by numerous factors including 

plant physiology, geochemical and microbiological 

processes and capillary flow of water 

through underlying soil. The concentrations of 

soluble ions in peat are dependent, for example, 

on the acidity, oxidation conditions, the ion exchange 

capacity and the number of complex compounds 

(Rose et al. 1979). 

The mobility of potential or actual contaminants 

derived from bedrock and soil depends on 

(1) their distribution and mode of occurrence, (2) 

their abundance, i.e. whether minerals are present 

in sufficient quantities to have a measurable effect, 

(3) their reactivity, i.e. the energetics, rates and 

mechanisms of sorption and mineral dissolution 

and precipitation relative to the flow rate of the 

water, and (4) hydrology, i.e. the main flow paths 

for contaminated water. Post-dissolution sorption 

and precipitation (attenuation) reactions depend 

on the chemical behaviour of each element, 

the composition and pH of the solution, aqueous 

speciation, temperature, and contact times with 

mineral surfaces. For example, little metal attenuation 

occurs in waters of low pH (



heavy metals in peat. Jones and Hao (1993) also 

demonstrated elevated concentrations of Cd, Cu, 

Fe, Pb, and Zn in peat due to industrial activities 

in Sheffield and Manchester. Historical mining 

and smelting has been recorded in peat profiles 

in many parts in the world, for example, in the 

Basque Country in Spain (Monna et al. 2004) and 

South West England (West et al. 1997). 

In the present study, results from the analysis of 

three peat profiles sampled in 2005 around the Tal- 

The bedrock in the Talvivaara area consists of 

both Archaean and Palaeoproterozoic rocks 

(Figs. 1 and 2). The Talvivaara deposit comprises 

two polymetallic ore bodies, Kuusilampi and Kolmisoppi. 

The mineral resource is 1 550 million 

tonnes at 0.22% of nickel, 0.13% of copper, 0.02% 

of cobalt and 0.49% of zinc (Talvivaara Mining 

Company 2010). Loukola-Ruskeeniemi and Heino 

(1996) classified the Talvivaara C-rich rocks 

into two main groups: black schists (Ni-rich, Nipoor, 

and Mn-rich subtypes) and graphite-rich 

calc-silicate rocks. The black schists at Talvivaara 

contain quartz, mica, graphite and sulphides as 

the main minerals, with rutile, apatite, zircon, 

feldspar and garnet as common accessory minerals. 

Quartz occurs in both the matrix and veins, 

together with sulphides, mica and feldspar. Pyrite 

and pyrrhotite are the dominant sulphide minerals 

in the Talvivaara deposit. Pyrite, pyrrhotite 

and sphalerite occur both as fine-grained disseminations 

(

7097 7100 7103 

N 



3551 3555 

1 km 

KOLMISOPPI 

M2 

M1 

KUUSILAMPI 

M3 

3551 3555 

Grey and compact sandy basal glacial till is the 

prevailing soil type at Talvivaara and is present 

as a thin layer covering the entire area (Murtoniemi 

1984). Till fabric alignments vary from 

290º to 310º, corresponding to bedrock striation 

directions and the general orientation of drumlins 

and bedrock topography. The upper part of the 

basal till horizon has locally been reworked with 

removal of fine material, during the final stages of 

the last deglaciation. Ablation moraines, characterized 

by sand and gravel, form discrete mounds 

Because of the highly undulating topography in 

the Talvivaara area, as in much of the Sotkamo 

region, peatlands are relatively small. Together 

with several lakes, occupying low-lying areas 

throughout the region, commonly occurring in 

depressions between elevated moraine ridges (Fig. 

7097 7100 7103 

2.2 Soil 

2.3 Peatlands 

Upper Kaleva (



Fig. 3. Soil stratigraphy exposed at study site M2 in 2011. Photo: Ale Grundström, GTK. 

Fig. 4. Shaded topographic map of the Talvivaara area showing study sites and drainage watershed (broken red line). Old 

quarries are also marked on the map in violet. Detailed maps from study site M2 (inset enlargement at lower right) indicate 

that the old quarries did not influence the quality of surface and ground water affecting peat in M2. Outcrops of black schist 

containing abundant sulphides (inset enlargement at upper right) induce acid runoff and acidification of surface waters, after 

exposure to the atmosphere and surface waters (Loukola-Ruskeeniemi et al. 1998). Basemap@National Land Survey of Finland, 

licence no 13/MML/12. 

8 

7095 7096 7097 7098 

Watershed area 

Rock outcrop 

!( Study sites 

Old quarry 

m.a.s.l. 

High : 250 m 

Low : 200 m 

3553 

M2 

3553 

M2 

3554 

M1 

M3 

0 250 500 1 000 000Metriä 

m 

3554 

7097000 7098000 7099000 

7098000 

7097000 

7096000 

7098 

7097 

7096 

7095 

m a.s.l 

High : 218 m 

Low : 210 m 

M2 

M2 

! 

0 100 200 300 m

7097 7100 7103 



3551 3555 

3551 

!( !( 

M2 

!( !( 

M1 

!( 

M3 

3555 

7103 

7100 

7097 

Fig 5. Magnetic map of the study area. Fig. 6. Electromagnetic in-phase component map of the 

study area. 

when the sandy till in depressions between moraine 

ridges became emergent. Peatland formation 

began on mineral soils on the sloping study 

site M2 at 7980 years ago (C14-age; Poz-4323). 

The rate of peat formation has averaged 0.31 mm 

Low altitude airborne geophysical surveys of the 

Talvivaara area were carried out along east-west 

flightlines in 1977. The black schist area is clearly 

delineated in both magnetic and electromagnetic 

maps. The magnetic map in Figure 5 illustrates the 

distribution of ferrimagnetic minerals in the bedrock. 

Magnetic anomalies in the black schists are 

due to the presence of monoclinic pyrrhotite and 

Sampling of the peat layers from study sites M1, 

M2 and M3 at Talvivaara was carried out in 

2.4 Airborne geophysics 

3 MATERIALS AND METHODS 

3.1 Sampling 

per year. The peat at study site M3 was formed 

by progressive paludication of forest, the evidence 

for which can be seen in wood residues at the bottom 

of the peat layer. 

are indicated by red colors in Figure 5. The electromagnetic 

in-phase component map in Figure 6 

corresponds generally to the mineral composition 

of the bedrock, but thick overburden and water 

bodies can obscure their distribution. The electrical 

anomalies in the black schist area are caused 

by both graphite and sulphides. 

2005, before the commencement of mining at Talvivaara 

(Fig. 7). 

9



Fig. 7. Study site M2 in 2011. The mining area is visible in the 

background approximately 100 m from the study site. Photo: 

Markku Mäkilä, GTK. 

Sampling was carried out using a Russian 

core sampler with a diameter of 5 cm and length 

of 50 cm. Peat samples were taken at the in situ 

peat deposit study sites as 10 cm sections from 

the surface downwards (Fig. 8). Altogether, 58 

peat samples were taken. The main peat type and 

In the laboratory, peat samples were homogenized 

before analysis. The samples were chemically analysed 

by ICP-MS and ICP-AES methods. Analyses 

were carried out in the laboratory of the 

Geological Survey of Finland. The samples were 

analysed for organic carbon and ash content % of 

Conductivity was measured at the three study 

sites from the surface to the bottom of the cored 

section at intervals of 25 cm. During sampling, 

conductivity and temperature were measured 

with an electric conductivity and temperature 

probe (Puranen et al. 1997 and 1999) (Fig. 9). The 

sensor was pressed into the peat using the shaft 

of the core sampler. The temperature sensor consisted 

of an integrated circuit (AD590), and the 

four Wenner electrodes (with a spacing of 1.5 cm) 

comprising the conductivity sensor operated at 

a high frequency (500 Hz) to avoid electrode polarization. 

Electrical conductivity correlates with 

the nutrient content, temperature and acidity (pH 

value) of peatland waters. 

10 

3.2 Laboratory analyses 

3.3 Electrical conductivity 

Fig. 8. Peat sampling. Photo: Markku Mäkilä, GTK. 

the proportions of any minor constituents were 

determined by visual inspection of the peat cores 

(Lappalainen et al. 1984). Humification was estimated 

according to the 10-degree scale of von 

Post (1922). In addition, the type of subsoil was 

recorded. 

dry weight, water content % of wet weight, pH, 

elemental sulphur and major and trace elements 

(mg/kg). Dry bulk density per cubic metre of peat 

(g/m 3 ) was calculated on the basis of the water 

content (Mäkilä 1994). 

Fig. 9. Probe for electrical conductivity and temperature logging 

of soft sediments. P: probe; E: electronics unit; C: Kevlar 

cable; S: sampler shaft; L: lifting tool.



4 RESULTS 

4.1 Chemical concentrations and peat properties of study sites 

Study site M1 was situated in a schist area outside 

the watershed (Figs. 2 and 4). The mire type at 

study site M1 represents a transformed pine bog. 

The peat layer was 1.8 m thick and mainly consisted 

of moderately decomposed woody-Sphagnum 

(moss) peat with a Carex (sedge) layer at the 

bottom. Beneath the peat was a 10 cm layer of 

sandy till with peat (Table 1). The mean humification 

degree (H) of the peat was 5.5 according on 

the 10-degree scale of von Post (1922). The average 

ash content was 2.4% of dry weight, the water 

content 87.1% of wet weight, and the dry bulk 

density 125.3 kg per m 3 in situ (Table 1). 

Study site M2 represents peat development on 

sloping terrain, which occurs where ground water 

is discharges at the surface on a rather steep 

slope (Fig. 4). This type of peatland usually forms 

at the foot of a hill. Good drainage and aeration 

of the peat-generating layer ensures a high degree 

of peat decomposition, although some remaining 

wood residues are well preserved (Fig. 10). Study 

site M2 is located within the watershed, subject 

Fig. 10. Well-preserved woody residue at study site M2. Photo: Markku Mäkilä, GTK. 

to discharge from the Kuusilampi ore deposit, 

where the bedrock consists of black schists that 

are highly fractured and rich in sulphides (Fig. 2). 

The mire type at the study site consisted of 

transformed spruce peatland. The peat layer was 

2.5 m thick and mainly consisted of well decomposed 

woody Carex peat. The subsoil was sandy 

till (Fig. 3). The mean humification degree (H) 

of the peat was 6.6. The average ash content was 

31.3% of dry weight, the water content 85.3% of 

wet weight, and the dry bulk density 135.3 kg per 

m 3 in situ (Table 1). 

Study site M3 was situated in a black schist area 

outside the watershed (Figs. 2 and 4). This site 

represented a transformed spruce peatland. The 

peat layer was 1.2 m thick and mainly comprised 

moderately decomposed woody Sphagnum and 

Carex peat. The subsoil was sandy till. The mean 

humification degree (H) of the peat was 5.2. The 

average ash content was 5.6% of dry weight, the 

water concentration 85.9% of wet weight, and the 

dry bulk density 132.0 kg per m 3 in situ (Table 1). 

11



Tables 1, 2 and 3. Concentrations of selected trace elements and sulphur, pH, carbon, water, and ash content and dry density. Conductivity is corrected at a temperature of 18 o C in peat 

at study sites M1, M2 and M3. Metal and sulphur concentrations are presented as mg/kg dry matter. The peat type is described using the following symbols: C Carex (sedge), S Sphagnum 

(moss), B Bryales (brown moss), ER Eriophorum (cotton grass), L wood residues, EQ Equisetum (horsetail), N Nanolignidi (dwarf shrub remains). Degree of humification 1-10 in von Post’s 

scale. Sphagnum-predominant peat is highlighted with light grey and Carex-predominant peat is highlighted with dark grey. 

12 

Depth Humifi- Peat Co Cu Fe Mn Ni Pb U Zn S C pH Water Dry Ash Conduccm 

cation type mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg % cont. % density % tivity 

of dry of wet in situ of dry mS/m 

weight weight kg/m3 Table 1. 

weight 18 °C 

10 2 LS 1.10 10.3 8060 35.7 5.48 18.9 0.21 41.0 2400 43.6 3.4 87.2 100.6 3.5 12.8 

20 7 LS 0.87 5.09 4300 6.00 5.33 9.14 0.37 10.1 3200 51.2 3.2 88.3 114.2 3.1 12.8 

30 7 LS 0.84 5.41 1410 7.85 4.65 3.32 0.26 11.2 3730 48.3 3.1 86.2 135.4 2.1 12.8 

40 5 ERS 0.98 8.25 1210 9.52 5.79 1.87 0.34 7.08 3830 48.7 3.1 85.5 142.5 1.7 8.0 

50 5 ERS 0.75 4.79 1190 8.69 4.65 0.95 0.41 5.43 3510 49.8 3.2 84.4 153.6 1.4 8.0 

60 5 ERLS 0.72 10.1 1320 10.1 6.26 1.31 0.96 7.63 4110 51.1 3.3 84.4 153.5 1.9 8.0 

70 5 ERLS 0.68 10.9 1290 8.65 5.48 0.99 0.97 4.98 4800 51.0 3.3 84.6 151.5 1.8 6.7 

80 5 ERLS 1.00 15.5 1260 8.59 6.58 1.07 1.16 5.59 6620 50.9 3.4 86.3 134.5 1.7 6.7 

90 5 ERLS 0.88 16.2 1220 7.72 5.74 0.90 1.38 5.24 6250 51.5 3.6 88.2 115.5 1.8 4.3 

100 5 CS 1.12 19.2 1220 7.78 6.34 1.35 1.30 4.56 8450 51.6 3.6 90.2 95.5 1.7 4.3 

110 7 SC 0.94 18.5 1510 9.18 6.37 2.26 1.25 4.99 6730 51.0 3.5 89.0 107.3 1.9 4.3 

120 7 SC 0.87 28.6 1620 8.23 7.19 2.99 2.03 4.48 6850 51.2 3.6 88.7 110.2 2.5 5.1 

130 7 SC 0.73 30.8 1600 7.77 6.99 2.74 2.42 4.04 7380 51.8 3.6 87.3 123.8 3.2 5.1 

140 6 SC 0.62 26.1 1670 7.92 7.33 3.13 2.33 5.17 7930 52.7 3.7 84.6 150.6 3.0 4.5 

150 6 SC 0.69 30.7 1890 8.39 9.04 4.02 2.30 3.95 9970 51.1 3.7 84.3 153.5 3.2 4.5 

160 5 SC 1.05 31.5 2010 8.78 12.4 3.59 1.37 6.46 11600 51.5 3.7 87.6 121.0 2.7 4.5 

170 5 SC 1.11 18.9 2200 8.87 9.68 1.92 0.77 7.29 11000 51.6 3.9 89.9 98.4 2.2 3.7 

180 5 SC 1.43 15.5 2660 10.2 11.4 1.64 0.55 21.3 9030 49.8 3.9 90.4 93.2 3.4 3.7 

190 Sandy peat 1.91 47.1 3140 26.5 23.6 3.29 2.07 93.4 8530 35.9 4.1 32.3 3.3 

200 Peaty till 6.40 31.8 5900 86.6 29.1 6.98 2.41 38.0 2450 11.5 4.4 81.9 3.3 

Average 5.5 0.91 17 2091 10.00 7.04 3.5 1.13 8.92 6522 50.5 3.5 87.1 125.3 2.4 6.7

Table 2. 






weight weight kg/m 3 weight 18 °C 

10 2 NS 2.72 29 26200 89.9 22.9 23.9 0.61 104 2230 43.8 3.5 85.3 100.6 6.6 3.5 

20 5 LCS 1.53 73 17000 7.09 17.6 12.7 2.36 36.4 4680 48.2 3.6 84.1 155.5 6.4 3.5 

30 6 LCS 1.35 180 13700 6.80 21.4 12.2 3.66 48.2 6740 46.9 3.7 85.1 144.8 10.1 3.5 

40 7 SC 2.00 276 25600 21.6 25.9 3.55 3.27 220 9540 40.3 4.2 85.7 135.5 20.8 4.5 

50 7 SC 4.06 93 9670 71.0 35.4 1.40 1.56 266 10300 29.7 4.4 86.3 124.7 41.7 4.5 

60 8 SC 9.88 94 20100 77.3 77.6 3.84 1.88 317 15700 34.9 4.3 87.1 119.6 29.8 4.5 

70 7 LSC 20.4 95 32200 76.9 162 1.33 1.69 568 27100 30.5 3.1 88.0 110.2 31.7 8.5 

80 6 SC 20.0 97 33500 85.0 156 1.28 2.00 676 26300 35.1 3.2 89.0 102.7 21.9 8.5 

90 7 SC 21.7 120 32300 68.1 148 0.65 2.08 795 26700 30.7 3.3 87.7 113.5 30.3 10.1 

100 7 SC 33.9 146 40000 56.0 220 0.53 2.64 1010 35300 26.1 3.3 87.5 114.0 36.7 10.1 

110 8 LSC 32.4 184 42400 57.9 230 0.62 3.47 1050 35000 28.0 3.3 87.8 112.0 32.5 10.1 

120 8 LSC 39.0 231 47600 54.3 303 0.64 4.47 1490 41100 26.5 3.3 87.7 112.7 34.1 9.5 

130 7 LSC 37.8 249 53300 48.7 305 0.69 5.67 1580 46500 25.0 3.2 87.2 117.3 35.2 9.5 

140 7 LSC 31.3 316 63700 40.4 286 0.83 6.94 1580 57900 23.8 3.4 86.1 127.9 36.4 11.7 

150 7 SC 16.9 292 80600 33.3 237 1.31 7.82 1830 75500 23.2 3.3 83.8 150.6 36.9 11.7 

160 7 SC 19.5 300 75100 32.8 244 1.32 7.71 1990 69600 23.5 3.7 84.9 139.6 37.3 11.7 

170 8 SC 20.3 324 78900 28.4 272 1.41 8.20 2380 74900 23.5 3.6 84.6 142.9 35.6 12.5 

180 7 SC 18.6 285 90700 22.0 260 1.36 6.92 2170 86500 23.2 3.8 84.6 143.1 34.9 12.5 

190 6 BC 18.7 234 97700 15.4 265 1.14 5.57 1990 93000 21.1 3.2 85.2 136.5 37.6 16.5 

200 6 BC 18.4 227 109000 11.6 293 0.76 5.07 2420 107000 20.6 3.1 84.4 144.9 35.7 16.5 

210 6 BC 27.0 194 120000 14.0 451 1.28 3.88 5270 121000 22.2 3.7 85.1 138.1 35.3 16.5 

220 6 SC 16.5 114 85600 22.5 292 0.43 3.48 2740 123000 18.8 3.5 83.5 153.5 36.9 21.5 

230 7 LSC 12.1 93 74600 23.5 277 0.66 2.64 1050 136000 14.9 3.6 80.3 183.7 43.3 21.5 

240 7 LSC 20.8 101 89800 16.6 612 3.44 4.84 1580 136000 16.1 3.2 79.5 192.1 40.9 27.8 

250 7 EQLSC 28.1 137 87700 23.4 758 7.06 10.5 4360 126000 24.8 2.8 82.4 165.1 33.7 27.8 

260 Peaty till 35.9 334 269000 29.9 1120 15.4 8.77 5400 33700 9.65 68.3 36.7 

Average 6.6 19.0 179 57879 40.2 239 3.4 4.4 1501 59744 28.1 3.5 85.3 135.3 31.3 11.9 

13



14 

Table 3. 




weight weight kg/m3 weight 18 °C 

10 2 NS 1.41 17.5 4110 46.3 20.9 16.9 1.2 39.1 5090 45.1 3.4 83.3 100.6 6.4 7.3 

20 7 LS 1.33 27.4 3880 11.3 27.1 10.1 1.53 29.2 8700 47.9 3.5 83.5 161.9 4.7 7.3 

30 7 LS 1.72 20.6 3800 27.4 31.8 3.33 0.91 54.5 9470 48.2 3.6 85.2 144.8 5.2 7.3 

40 6 LCS 1.76 15.6 3500 22.9 34.7 1.71 0.96 64.5 9610 48.6 3.7 85.3 143.8 5.3 5.4 

50 6 LCS 1.88 12.9 3800 33.4 35.5 1.8 0.98 79.5 9910 47.9 3.8 84.8 148.7 5.9 5.4 

60 4 LCS 2.09 16.6 4500 55.3 35.4 1.89 0.58 73.6 10100 47.8 4.2 88.2 114.5 5.1 5.4 

70 5 LSC 2.28 15.3 5750 86.3 37.4 0.81 0.53 83.2 12300 47.5 4.1 86.7 129.2 5.6 8.9 

80 5 LSC 2.00 20.7 7100 105 40.6 0.86 0.91 93.3 13400 48.0 4.2 87.5 121.2 6.1 10.4 

90 5 LSC 1.64 24.2 7780 128 40.4 0.87 1.17 84.8 14500 47.5 4.3 86.6 130.0 6.6 13.6 

100 5 LSC 1.43 24.0 7610 120 34.0 0.89 1.03 100 13600 48.3 4.3 86.9 127.3 5.2 13.6 

110 5 LSC 1.33 18.8 6950 108 30.1 0.96 0.79 49.8 14900 49.5 4.6 87.8 118.6 4.6 13.6 

120 5 LSC 1.20 26.7 8260 124 37.4 1.15 1.42 118 14400 48.8 4.5 85.2 143.8 6.5 15.1 

Average 5.2 1.67 20.0 5587 72.3 33.8 3.4 1.0 72.5 11332 47.9 4.0 85.9 132.0 5.6 9.4

Tables 4, 5 and 6. Concentrations of selected trace elements, sulphur, pH value, carbon, water, and ash content, dry density and conductivity corrected at a temperature of 18 o C at study 

sites M1, M2 and M3. Metal and sulphur concentrations are presented as g/m3 of peat. The peat type is described with use of the following symbols: C Carex (sedge), S Sphagnum (moss), 

B Bryales (brown moss), ER Eriophorum (cotton grass), L wood residues, EQ Equisetum (horsetail), N Nanolignidi (dwarf shrub remains). Degree of humification 1-10 in von Post’s scale. 

Sphagnum-predominant peat is highlighted with light grey and Carex-predominant peat is highlighted with dark grey. Average values don´t include results of the sandy peat and peaty till 

samples. 




cation type g/m3 g/m3 g/m3 g/m3 g/m3 g/m3 g/m3 g/m3 g/m3 % cont. % density % tivity 


weight weight kg/m3 Table 4. 

weight 18 °C 

10 2 LS 0.22 1.04 811 3.59 5.48 18.9 0.21 4.12 241 43.6 3.4 87.2 100.6 3.5 12.8 

20 7 LS 0.10 0.58 491 0.69 5.33 9.14 0.37 1.15 366 51.2 3.2 88.3 114.2 3.1 12.8 

30 7 LS 0.11 0.73 191 1.06 4.65 3.32 0.26 1.52 505 48.3 3.1 86.2 135.4 2.1 12.8 

40 5 ERS 0.14 1.18 172 1.36 5.79 1.87 0.34 1.01 546 48.7 3.1 85.5 142.5 1.7 8.0 

50 5 ERS 0.12 0.74 183 1.33 4.65 0.95 0.41 0.83 539 49.8 3.2 84.4 153.6 1.4 8.0 

60 5 ERLS 0.11 1.55 203 1.55 6.26 1.31 0.96 1.17 631 51.1 3.3 84.4 153.5 1.9 8.0 

70 5 ERLS 0.10 1.65 195 1.31 5.48 0.99 0.97 0.75 727 51.0 3.3 84.6 151.5 1.8 6.7 

80 5 ERLS 0.13 2.09 170 1.16 6.58 1.07 1.16 0.75 891 50.9 3.4 86.3 134.5 1.7 6.7 

90 5 ERLS 0.10 1.87 141 0.89 5.74 0.90 1.38 0.61 722 51.5 3.6 88.2 115.5 1.8 4.3 

100 5 CS 0.11 1.83 116 0.74 6.34 1.35 1.30 0.44 807 51.6 3.6 90.2 95.5 1.7 4.3 

110 7 SC 0.10 1.99 162 0.99 6.37 2.26 1.25 0.54 722 51.0 3.5 89.0 107.3 1.9 4.3 

120 7 SC 0.10 3.15 178 0.91 7.19 2.99 2.03 0.49 755 51.2 3.6 88.7 110.2 2.5 5.1 

130 7 SC 0.09 3.81 198 0.96 6.99 2.74 2.42 0.50 914 51.8 3.6 87.3 123.8 3.2 5.1 

140 6 SC 0.09 3.93 251 1.19 7.33 3.13 2.33 0.78 1194 52.7 3.7 84.6 150.6 3.0 4.5 

150 6 SC 0.11 4.71 290 1.29 9.04 4.02 2.30 0.61 1530 51.1 3.7 84.3 153.5 3.2 4.5 

160 5 SC 0.13 3.81 243 1.06 12.4 3.59 1.37 0.78 1403 51.5 3.7 87.6 121.0 2.7 4.5 

170 5 SC 0.11 1.86 216 0.87 9.68 1.92 0.77 0.72 1082 51.6 3.9 89.9 98.4 2.2 3.7 

180 5 SC 0.13 1.44 248 0.95 11.4 1.64 0.55 1.98 841 49.8 3.9 90.4 93.2 3.4 3.7 

190 Sandy peat 35.9 4.1 32.3 3.3 

200 Peaty till 11.5 4.4 81.9 3.3 

Average 5.5 0.12 2.1 248 1.2 7.04 3.45 1.13 1.0 801 50.5 3.5 87.1 125.3 2.4 6.7 

15



16 

Table 5. 


cation type g/m 3 g/m 3 g/m 3 g/m 3 g/m 3 g/m 3 g/m 3 g/m 3 g/m 3 % cont. % density % tivity 



10 2 NS 0.27 2.90 2636 9.04 2.30 2.40 0.06 10.5 224 43.8 3.5 85.3 100.6 6.6 3.5 

20 5 LCS 0.24 11.3 2644 1.10 2.74 1.98 0.37 5.7 728 48.2 3.6 84.1 155.5 6.4 3.5 

30 6 LCS 0.20 26.1 1983 0.98 3.10 1.77 0.53 7.0 976 46.9 3.7 85.1 144.8 10.1 3.5 

40 7 SC 0.27 37.4 3470 2.93 3.51 0.48 0.44 29.8 1293 40.3 4.2 85.7 135.5 20.8 4.5 

50 7 SC 0.51 11.5 1206 8.85 4.41 0.17 0.19 33.2 1285 29.7 4.4 86.3 124.7 41.7 4.5 

60 8 SC 1.18 11.2 2404 9.24 9.3 0.46 0.22 37.9 1878 34.9 4.3 87.1 119.6 29.8 4.5 

70 7 LSC 2.25 10.5 3550 8.48 17.9 0.15 0.19 62.6 2988 30.5 3.1 88.0 110.2 31.7 8.5 

80 6 SC 2.05 10.0 3439 8.73 16.0 0.13 0.21 69.4 2700 35.1 3.2 89.0 102.7 21.9 8.5 

90 7 SC 2.46 13.6 3667 7.73 16.8 0.07 0.24 90.3 3032 30.7 3.3 87.7 113.5 30.3 10.1 

100 7 SC 3.87 16.6 4561 6.39 25.1 0.06 0.30 115 4025 26.1 3.3 87.5 114.0 36.7 10.1 

110 8 LSC 3.63 20.6 4750 6.49 25.8 0.07 0.39 118 3921 28.0 3.3 87.8 112.0 32.5 10.1 

120 8 LSC 4.39 26.0 5362 6.12 34.1 0.07 0.50 168 4630 26.5 3.3 87.7 112.7 34.1 9.5 

130 7 LSC 4.44 29.2 6254 5.71 35.8 0.08 0.67 185 5456 25.0 3.2 87.2 117.3 35.2 9.5 

140 7 LSC 4.00 40.4 8149 5.17 36.6 0.11 0.89 202 7407 23.8 3.4 86.1 127.9 36.4 11.7 

150 7 SC 2.54 44.0 12134 5.01 35.7 0.20 1.18 276 11367 23.2 3.3 83.8 150.6 36.9 11.7 

160 7 SC 2.72 41.9 10483 4.58 34.1 0.18 1.08 278 9715 23.5 3.7 84.9 139.6 37.3 11.7 

170 8 SC 2.90 46.3 11279 4.06 38.9 0.20 1.17 340 10707 23.5 3.6 84.6 142.9 35.6 12.5 

180 7 SC 2.66 40.8 12980 3.15 37.2 0.19 0.99 311 12379 23.2 3.8 84.6 143.1 34.9 12.5 

190 6 BC 2.55 32.0 13341 2.10 36.2 0.16 0.76 272 12699 21.1 3.2 85.2 136.5 37.6 16.5 

200 6 BC 2.67 32.9 15794 1.68 42.5 0.11 0.73 351 15504 20.6 3.1 84.4 144.9 35.7 16.5 

210 6 BC 3.73 26.8 16569 1.93 62.3 0.18 0.54 728 16707 22.2 3.7 85.1 138.1 35.3 16.5 

220 6 SC 2.53 17.5 13141 3.45 44.8 0.07 0.53 421 18883 18.8 3.5 83.5 153.5 36.9 21.5 

230 7 LSC 2.22 17.1 13701 4.32 50.9 0.12 0.48 193 24977 14.9 3.6 80.3 183.7 43.3 21.5 

240 7 LSC 4.00 19.4 17253 3.19 117.6 0.66 0.93 304 26129 16.1 3.2 79.5 192.1 40.9 27.8 

250 7 EQLSC 4.64 22.6 14483 3.86 125.2 1.17 1.73 720 20808 24.8 2.8 82.4 165.1 33.7 27.8 

260 Peaty till 9.65 68.3 36.7 

Average 6.6 2.5 24.3 8209 5.0 34.3 0.4 0.6 213 8817 28.1 3.5 85.3 135.3 31.3 11.9



Table 6. 


cation type g/m 3 g/m 3 g/m 3 g/m 3 g/m 3 g/m 3 g/m 3 g/m 3 g/m 3 % cont. % density % tivity 



10 2 NS 0.14 1.76 413 4.66 2.10 1.70 0.12 3.93 512 45.1 3.4 83.3 100.6 6.4 7.3 

20 7 LS 0.22 4.44 628 1.83 4.39 1.64 0.25 4.73 1409 47.9 3.5 83.5 161.9 4.7 7.3 

30 7 LS 0.25 2.98 550 3.97 4.60 0.48 0.13 7.89 1371 48.2 3.6 85.2 144.8 5.2 7.3 

40 6 LCS 0.25 2.24 503 3.29 4.99 0.25 0.14 9.27 1382 48.6 3.7 85.3 143.8 5.3 5.4 

50 6 LCS 0.28 1.92 565 4.97 5.28 0.27 0.15 11.82 1473 47.9 3.8 84.8 148.7 5.9 5.4 

60 4 LCS 0.24 1.90 515 6.33 4.05 0.22 0.07 8.43 1156 47.8 4.2 88.2 114.5 5.1 5.4 

70 5 LSC 0.29 1.98 743 11.15 4.83 0.10 0.07 10.75 1589 47.5 4.1 86.7 129.2 5.6 8.9 

80 5 LSC 0.24 2.51 860 12.72 4.92 0.10 0.11 11.31 1624 48.0 4.2 87.5 121.2 6.1 10.4 

90 5 LSC 0.21 3.14 1011 16.63 5.25 0.11 0.15 11.02 1884 47.5 4.3 86.6 130.0 6.6 13.6 

100 5 LSC 0.18 3.06 969 15.28 4.33 0.11 0.13 12.73 1732 48.3 4.3 86.9 127.3 5.2 13.6 

110 5 LSC 0.16 2.23 824 12.81 3.57 0.11 0.09 5.90 1767 49.5 4.6 87.8 118.6 4.6 13.6 

120 5 LSC 0.17 3.84 1188 17.84 5.38 0.17 0.20 16.97 2071 48.8 4.5 85.2 143.8 6.5 15.1 

Average 5.2 0.22 2.67 731 9.29 4.47 0.44 0.13 9.56 1497 47.9 4.0 85.9 132.0 5.6 9.4 

17



At study site M2 in the black schist area, the 

average concentrations of copper, nickel, zinc 

and sulphur in the peat were many times higher 

than average values reported by Virtanen (2005) 

from Ostrobothnia in western Finland (Table 7). 

These differences were particularly significant 

for zinc, nickel, cobolt and sulphur. At the black 

schist study site M3, Zn, Ni and S concentrations 

showed the greatest differences when compared 

with average values from Ostrobothia. At study 

site M1, located in an area of mica schists with 

black schist intercalations, element concentrations 

were closer to the average values of Ostrobothnia 

(Table 7). 

The concentrations of Co, Cu, Fe, Mn, Ni, Zn 

and S were greater in peat at black schist study site 

M3 than at mica schist study site M1. However, 

the above-mentioned concentrations, apart from 

those for Mn, were significantly greater at study 

18 

site M2 in an area where hydrologically modified 

peat overlies black schist than at study sites M1 or 

M3, (Tables 1−6). 

At study sites M1 and M3 the concentrations 

of cobalt remained relatively constant with increasing 

depth (Fig. 11). At M2 the cobalt concentration 

increased more than tenfold from the 

surface down to a depth of 0.3 m, after which the 

concentration remained relatively constant. 

The copper concentration also increased as a 

function of depth (Fig. 12). At the black schist 

study sites M2 and M3 the peak copper concentration 

was recorded at a depth of less than half 

a metre, while at the mica schist study site M1 the 

peak was close to the bottom of the peat layer. 

The iron concentration increased at all study 

sites as a function of depth below 50 cm, the largest 

increase being recorded at study site M2 (Fig. 

13). 

Table 7. The average concentrations of selected trace elements and sulphur at study sites M1, M2 and M3 at Talvivaara. Results 

from peatlands of northern Ostrobothnia were used as reference values for comparison (Virtanen 2005). Red background 

colour indicates higher concentrations and blue background lower concentrations compared to average values provided by 

Virtanen (2005). The Talvivaara ore has rather low Pb concentrations, which is evident in the comparative data: the Pb content 

of peat at Talvivaara is lower than in Ostrobothnia. 

Co Cu Fe Mn Ni Pb Zn S 

Study site mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg 

M1 0.9 17.0 2091 10.0 7.0 3.5 8.9 6522 

M2 19.0 179.4 57 879 40.2 238.9 3.4 1501 59 744 

M3 1.7 20.0 5587 72.3 33.8 3.4 72.5 11 332 

Virtanen (2005) 1.3 7.8 7710 83.9 3.9 4.2 8.9 1611 

norm. concent.) 

Depth [cm] 

Co concentration [mg/kg] 

0.1 1 10 100 

0 

50 

100 

150 

200 

250 

Fig. 11. Cobalt concentrations in peat at study sites M1, M2 and M3. The scale is logarithmic for Co. 

M1 

M2 

M3



Depth [cm] 

1 

0 

10 100 1000 

M1 

50 

100 

150 

200 

250 

Fig. 12. Copper concentrations in peat at study sites M1, M2 and M3. The scale is logarithmic for Cu. 

Depth [cm] 

0 

50 

100 

150 

200 

250 

Cu concentration [mg/kg] 

1000 10000 100000 

Fig. 13. Iron concentrations at study sites M1, M2 and M3. The scale is logarithmic for Fe. 

Depth [cm] 

Fe concentration [mg/kg] 

Mn concentration [mg/kg] 

1 

0 

10 100 1000 

50 

M1 

M2 

M3 

100 

150 

200 

250 

Fig. 14. Manganese concentrations at study sites M1, M2 and M3. The scale is logarithmic for Mn. 

M2 

M3 

M1 

M2 

M3 

19



Manganese concentrations were high in the uppermost 

surficial peat at all study sites (Fig. 14). 

Manganese was enriched at the peatland surface. 

However, the minimum manganese concentration 

at all study sites was recorded at a depth of 20 cm. 

Below the surface, the manganese concentration 

remained relatively constant with depth at study 

site M1, while at M3 it increased towards the bottom 

of the peat layer. At study site M2, the manganese 

concentration increased from the surface 

to a depth of 80 cm, below which the concentration 

steadily decreased towards the bottom. 

The nickel concentration increased towards the 

bottom at all study sites, the largest increase being 

recorded at study site M2 (Fig. 15). Nickel was 

enriched in the bottom peatland layers. 

The lead concentration was greatest near the 

surface of the peat layer at all study sites (Fig. 16). 

20 

Depth [cm] 

0 

50 

100 

150 

200 

250 

Lead was enriched at the peatland surface. Lead 

concentrations decreased downwards to a depth 

of less than a metre, after which they increased 

again. The average lead concentration was the 

same at each study site, which reflects the concentrations 

of bedrock and soil (Tables 1–3). The Talvivaara 

black schists tend not be enriched in Pb 

when compared to the average mica schists, which 

could also indicate that lead effectively binds to 

humic substances and is not easily transported 

through the soil. 

Uranium concentrations in the peat increased 

towards the bottom, with the exception of study 

site M3 (Fig. 17). At study site M3 the uranium 

concentration began to increase below a depth 

of 70 cm. The maximum uranium concentrations 

were recorded close to the soil. 

Except near the peat surface, the concentra- 

Ni concentration [mg/kg] 

1 10 100 1000 

Fig. 15. Nickel concentrations at study sites M1, M2 and M3. The scale is logarithmic for Ni. 

Depth [cm] 

0.1 

0 

1 10 100 

M1 

50 

100 

150 

200 

250 

Pb concentration [mg/kg] 

Fig. 16. Lead concentrations at study sites M1, M2 and M3. The scale is logarithmic for Pb. 

M1 

M2 

M3 

M2 

M3



Depth [cm] 

0.1 1 10 

0 

50 

100 

150 

200 

250 

U concentration [mg/kg] 

Fig. 17. Uranium concentrations at study sites M1, M2 and M3. The scale is logarithmic for U. 

Depth [cm] 

0 

50 

100 

150 

200 

250 

tion of zinc increased as a function of depth at 

the black schist study sites M2 and M3 (Fig. 18). 

The zinc concentration decreased with depth at 

the mica schist study site M1, at least to a depth 

of one and a half metres, after which the concentration 

increased again. The average zinc content 

at study site M2 was 168 times greater than at M1 

(Table 7). 

The acidity of the peat layers decreased downwards, 

as seen at M1 and M3 (Fig. 18). At study 

site M2, acidity decreased down to a depth of 

about 50 cm, after which there was a sharp reversal 

in trend. Because the surrounding bedrock was 

sulphide-rich, pH values were also anomalous at 

M2. The pH of peat is usually lowest in the surface 

layer (regional average 3.1–3.7) (Virtanen et 

al. 2003). The pH of the surface peat is dependent 

Zn concentration [mg/kg] 

1 10 100 1000 10000 

Fig. 18. Zinc concentrations at study sites M1, M2 and M3. The scale is logarithmic for Zn. 

M1 

M2 

M3 

M1 

M2 

M3 

upon the availability of hydrogen ions in Sphagnum 

peat, in that free hydrogen ions are produced 

by the cation exchange in the Sphagnum peat and 

organic acids are released by the aerobic decomposition 

of Sphagnum (Shotyk 1988). 

The pH value increases with depth in the peat 

layer. A high sulphur concentration causes a lowering 

of pH and an increase in conductivity (see 

Figs. 19–20). The average pH values for bottom 

peat layer in Finland range from 4.5 to 4.9 (Virtanen 

et al. 2003). At study site M1, pH levels 

were closest to the Finnish average, whereas the 

largest differences were found at the black schist 

study site M2; at this site the pH of the bottom 

peat layer (2.8–3.7) was the same or lower than 

the Finnish average values for surface peat. 

The sulphide concentration of study site M1 

21



22 

Depth [cm] 

2.5 

0 

3 3.5 4 4.5 5 

M1 

50 

100 

150 

200 

250 

Fig. 19. Acidity (pH value) at study sites M1, M2 and M3. 

Depth [cm] 

pH value 

1000 

0 

10000 100000 1000000 

M1 

50 

100 

150 

200 

250 

S concentration [mg/kg] 

Fig. 20. Sulphur concentrations at study sites M1, M2 and M3. The scale is logarithmic for S. 

was lower than at M3 and markedly less than at 

M2 (Fig. 20). Sulphur concentrations increased as 

a function of depth at all the study sites, most notably 

at M2 (Fig. 20). The increasing effect of the 

underlying soil was seen at the bottom of study 

sites M1 and M2. Essentially, sulphur in peat is 

transported from the underlying soil via plant 

roots. Sulphur is also likely to have risen into the 

peat layer by capillary flow, and then to have become 

bound to the peat. The high sulphur concentrations 

appear to be influenced most strongly 

by the bedrock in the black schist areas, while at 

study site M2, acidic drainage has also contributed 

significantly to the elevated S concentrations. 

The highest average sulphur concentrations reported 

for Finnish peatlands are from the black 

schist areas of North Karelia (Herranen 2010), 

M2 

M3 

M2 

M3 

which together account for approximately a third 

of the peatlands with the highest average sulphur 

concentrations in Finland. Virtanen and Lerssi 

(2006) observed that some element concentrations 

in peat are typically elevated in areas underlain 

by black schists; sulphur concentrations for 

example, may be up to 50–100 times greater than 

background levels. 

At study sites M1 and M3 the carbon content 

remained relatively constant with increasing 

depth. However, at study site M2, the carbon content 

decreased with depth, along with a coincident 

increase in ash content (Fig. 21). 

At the black schist study sites M2 and M3, 

the water content in peat increased from the surface 

down to a depth of about 0.6 m, mainly due 

to peatland drainage activities which had been



Depth [cm] 

0 

50 

100 

150 

200 

250 

Fig. 21. Carbon content at study sites M1, M2 and M3. 

Depth [cm] 

particularly intensive in the Talvivaara area in 

the 1960s (Fig. 22). The water table in the peat 

shows slight seasonal variations but was located 

at a depth of about half a metre at each of the 

study sites. Below this depth, the water content 

decreased most markedly at study site M2. Acidic 

waters had also displaced the peat pore waters; 

this was particulary evident at study site M2, 

where the ash content was high and the water content 

low (Table 2). There was a distinct correlation 

between the water content and the concentrations 

of analysed metals. 

At study site M1, the ash content of the peat 

layer was representative of the average ash content 

of peatlands in Finland, but the ash content 

was anomalously high at study site M2 (Fig. 23). 

According to Mäkilä (1994), the average ash con- 

C content [%] 

0 10 20 30 40 50 60 70 

79 81 

0 

50 

100 

150 

200 

250 

Fig. 22. Water content at study sites M1, M2 and M3. 

Water content [%] 

M1 

M2 

M3 

83 85 87 89 91 93 

M1 

M2 

M3 

tents of different peat types are 4.0% in Sphagnum- 

Carex peat, 3.8% in Carex peat, 3.4% in Carex- 

Sphagnum peat and 1.6% in Sphagnum peat. The 

degree of humification of peat also affects the ash 

content, although its effect is smaller than that 

due to the peat type. The elements contained in 

ash and their various resultant compounds constitute 

the inorganic component of the chemical 

composition of peat. Peat ash is derived from 

peatland vegetation (primary ash) and surrounding 

mineral matter (secondary ash). Material is 

classified as peat when the proportion of organic 

dry mass is at least 75%. At study site M2 in particular, 

the ash content was very high, so that with 

the exception of the peat surface the ash content 

exceeded the 25% threshold. 

Electrical conductivity increased from top to 

23



bottom at the black schist study sites M2 and 

M3 (Fig. 24). At study site M1, conductivity de- 

24 

Depth [cm] 

0 

50 

100 

150 

200 

250 

0 5 10 15 

Fig. 23. Ash content at study sites M1, M2 and M3. 

Depth [cm] 

0 

50 

100 

150 

200 

250 

Figure 25 presents statistically significant correlations 

between each of the parameters analysed 

at study sites M1, M2 and M3, computed using 

the Spearman method. Dark blue and light blue 

colours indicate a negative correlations with significance 

levels of

M1 

Co 

Cu 

Ni 

Pb 

U 

Fe 

Mn 

S 

Zn 

pH 

WaterCont. 

DryDensity 

Ash 

C 

Conductivity 

Depth 

Humification 

M3 Co 

Co 

Cu 

Ni 

Pb 

U 

Fe 

Mn 

S 

Zn 

pH 

WaterCont. 

DryDensity 

Ash 

C 

Conductivity 

Depth 


Co 

Cu 

Ni 

Pb 



U 

Fe 

Cu 

Ni 

Pb 

U 

Fe 

Mn 

Mn 

S 

S 

Zn 

Zn 

pH 

WaterCont. 

pH 

WaterCont. 

DryDensity 

Ash 

DryDensity 

Ash 

C 

Conductivity 

C 

Conductivity 

Depth 


tivity correlate with other analysed elements and 

peat properties. 

At study site M1, iron correlated most strongly 

with ash content, lead and zinc (Fig. 26). Iron 

showed a strong positive correlation with Ni, S, 

Zn, U, Co and conductivity at study site M2. At 

study site M3, iron had a strongly positive correlation 

with conductivity, manganese and sulphur, 

and a strongly negative correlation with cobalt 

and lead. 

At study site M1, uranium showed a strongly 

positive correlation with copper, sulphur, nickel 

and pH and a negative correlation with conductivity 

(Fig. 27). Uranium had a strongly positive 

correlation with Cu, Zn, Fe, Ni, conductivity, S 

and Co at study site M2 and a negative correlation 

with Mn. At study site M3, uranium was 

strongly correlated with Co. 

At study site M1, a positive correlation was ob- 

M2 Co 

Co 

Cu 

Ni 

Pb 

U 

Fe 

Mn 

S 

Zn 

pH 

WaterCont. 

DryDensity 

Ash 

C 

Conductivity 

Depth 


Cu 

Ni 

Pb 

U 

Fe 

Mn 

S 

Zn 

pH 

WaterCont. 

DryDensity 

Ash 

C 

Conductivity 

Depth 


Pos. correlation is significant at the 0.01 level (2-tailed). 


Neg. correlation is significant at the 0.01 level (2-tailed). 


Fig. 25. Statistically significant correlations between the studied properties at study sites M1, M2 and M3. 

Depth 


served between sulphur and copper, pH, uranium 

and nickel, but a significant negative correlation 

was found between sulphur and conductivity (Fig. 

28). Significant positive correlations between sulphur 

and conductivity, nickel, iron and zinc were 

recorded at the black schist study site M2 (Figs. 

24 and 28). It is probable that the iron and the 

sulphur have combined to form an iron-sulphur 

compound in the peat (Virtanen & Lerssi 2006). 

Iron-sulphur compounds in peat appear to reduce 

the pH of peat when present at high concentrations. 

This effect becomes apparent when the 

contents of both iron and sulphur exceed 1% of 

dry mass (Virtanen & Lerssi 2006). In the present 

data, an effect on pH levels is discernible at study 

site M2 when the contents of both iron and sulphur 

were approximately 20 000 mg/kg or 2 000 g/ 

peatland-m 3 (Tables 2 and 5). At the black schist 

study site M3, a significant positive correlation 

25



26 

Fe 

Spearman’s correlation coefficient 



1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

WaterCont. 

C 

Conductivity 


U 

Cu 

S 

Co 

C 

M1 

M2 

M3 

Co 

Pb 

WaterCont. 

pH 

Mn 

Pb 



DryDensity 

C 

WaterCont. 

Cu 

DryDensity 

U 

Ni 

Ash 

Zn 

Cu 

pH 





Depth 

DryDensity 

Mn 

pH 

Ni 

Zn 

Pb 

Ash 

Fe 

Ash 

Co 

U 

Zn 

S 

Conductivity 

Ni 

Depth 

Fe 

S 

Depth 

Mn 

Conductivity 

Fe 

Fig. 26. The statistically most significant correlations between iron and other measured variables at study sites M1, M2 and 

M3.



U 




1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

M1 

M2 

C 

Conductivity 

WaterCont. 

Zn 

Co 

WaterCont. 

Mn 

pH 

WaterCont. 

pH 

S 

Depth 

Co 

Mn 

C 

Zn 

Conductivity 

Fe 

M3 

Fe 

Mn 

Pb 

C 


Ash 

DryDensity 

pH 

Ni 

Depth 

Pb 


Ash 

DryDensity 

Co 

S 

Conductivity 

Ni 

Fe 

Depth 

Zn 

Cu 


Ni 





S 

Cu 

Ash 

Pb 

Cu 

DryDensity 

Fig. 27. The statistically most significant correlations between uranium and other investigated parameters at study sites M1, 

M2 and M3. 

U 

U 

U 

27



28 

S 




1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

Conductivity 

Zn 

WaterCont. 

Mn 

Co 

DryDensity 


Pb 

Fe 

C 

C 

Pb 

M1 

M2 

M3 

WaterCont. 

Mn 

pH 

Pb 

DryDensity 

Co 

U 


Cu 

Ash 

Ni 

C 


Cu 

DryDensity 

Co 

Ash 

U 

Ash 

Ni 





U 

pH 

Cu 

Depth 

Zn 

Fe 

Ni 

Conductivity 

Depth 

Zn 

WaterCont. 

Fe 

Conductivity 

Mn 

Depth 

pH 

Fig. 28. The statistically most significant correlations between sulphur and other investigated variables at study sites M1, M2 

and M3. 

S 

S 

S



pH 




1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

M1 

Conductivity 

DryDensity 


Mn 

Zn 

WaterCont. 

Co 

C 

Pb 

M2 

M3 

Co 

Fe 

Ni 

DryDensity 

Co 

U 


Cu 

Ash 

Ni 

Zn 

C 

Conductivity 

S 

Depth 

Zn 

U 

Pb 

Fe 

Ash 

U 

WaterCont. 

Mn 

Ash 

Ni 

Cu 

S 

Depth 

pH 

DryDensity 

Cu 

C 


Pb 

pH 

Fe 

WaterCont. 

Conductivity 

Mn 





S 

Depth 

pH 

Fig. 29. The statistically most significant correlations between pH and the other measured parameters at study sites M1, M2 

and M3. 

29



30 

Ash 




1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

M1 

Conductivity 

C 

WaterCont. 

DryDensity 

Co 

Mn 


U 

S 

M2 

C 

M3 

C 

WaterCont. 

Pb 

pH 

Mn 


WaterCont. 

Pb 

DryDensity 


pH 

Co 

S 

Cu 

Co 

U 

Depth 

Cu 

DryDensity 

Conductivity 





U 

Zn 

Cu 

Ni 

Depth 

pH 

Pb 

Fe 

Ash 

Zn 

Fe 

Ni 

S 

Depth 

Conductivity 

Ash 

Mn 

Fe 

Ni 

Zn 

Ash 

Fig. 30. The statistically most significant correlations between ash content and the parameters investigated at study sites M1, 

M2 and M3.



Conductivity 




1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

1.0 

0.8 

0.6 

0.4 

0.2 

0 

-0.2 

-0.4 

-0.6 

-0.8 

-1.0 

C 

Co 

M1 

M2 

M3 

Depth 

pH 

Pb 

S 

Cu 

U 

WaterCont. 

pH 

Mn 

Pb 

Ni 

DryDensity 



Cu 

DryDensity 

U 

Ni 

WaterCont. 

Ash 

Fig. 31. The statistically most significant correlations between conductivity and the other measured parameters at study sites 

M1, M2 and M3. 

C 

Ash 

WaterCont. 

C 

Co 

Fe 

Co 

Ash 

U 

Zn 

Cu 

pH 


Pb 

Zn 

Mn 

DryDensity 

Conductivity 

Zn 

Fe 





S 

S 

Depth 

Mn 

Ni 

Depth 

Conductivity 

Fe 

Conductivity 

31



was observed between sulphur and pH, manganese, 

conductivity and iron, but a significant negative 

correlation between sulphur and lead. 

At the mica schist study site M1, pH values 

displayed a positive correlation with sulphur, copper, 

nickel and uranium and a negative correlation 

with conductivity (Fig. 29). At study site M2 there 

was no marked association between pH and any 

of the analysed elements, although a negative correlation 

with cobalt was observed. At study site 

M3, pH was positively correlated with S, Mn and 

conductivity and negatively with Pb and Co. 

At study site M1 there was a marked correla- 

32 

tion between the ash content and iron, lead and 

pH (Fig. 30). At study site M2, a marked positive 

correlation was observed between the ash content 

and conductivity, sulphur, nickel, iron, zinc and 

uranium. 

There was a strong negative correlation between 

electrical conductivity and depth, pH, S 

and Cu at study site M1 (Fig. 31), and a clearly 

positive correlation of conductivity with depth, 

nickel, sulphur, iron and zinc at M2. Conductivity 

was positively correlated with iron, depth, manganese, 

sulphur and pH at study site M3. 

5 APPLICATION OF ELECTRIC CONDUCTIVITY MEASUREMENTS IN 

ENVIRONMENTAL STUDIES 

The logging probe (Fig. 9, p. 10) can be used for 

mapping the electrical conductivity and temperature 

of peatlands and underlying unconsolidated 

sediments. Conductivity data have been applied 

in the interpretation of electromagnetic (AEM) 

maps, and for tracing pollutants within peatlands. 

Electric conductivity also reflects the nutrient conditions 

(salinity, acidity), which, together with 

temperature, control the growth and decay processes 

within peatlands (Puranen et al. 1997, Puranen 

et al. 1999). Electrical conductivity correlates 

with the temperature and acidity (pH value) 

of peatland waters. A rise in temperature of one 

degree Celcius increases the electrical conductivity 

of the solution by approximately 2% (Hem 1985). 

Electrical conductivity measurements provide a 

reliable indication of anomalies in peat, and can 

be used as a preliminary indicator of peat conductivity 

(Puranen et al. 1996). The method is also 

more cost-effective than other geophysical techniques. 

The high sulphur content of peatlands in 

the black schist area had an effect on the high conductivity, 

especially in the sedge-dominated bottom 

and middle layers (Lerssi & Virtanen 2006). 

The peat layers investigated in the Talvivaara 

area contain high Zn, Cu and Ni concentrations 

but low Pb concentration compared with the values 

from western Finland reported by Virtanen 

(2005). This is because at Talvivaara the black 

schist has high Ni, Cu, and Zn concentrations but 

does not contain more Pb in average than the ad- 

6 DISCUSSION 

Higher acidity of peat layers and increasing metal 

contents enhances the conductivity of peat. Highly 

conductive runoff and groundwaters in poorly 

conducting peat is an optimal research target for 

conductivity probing (Puranen et al. 1996, Mäkilä 

& Toivonen 1998). 

A high sulphur concentration lowers the pH 

and increases the conductivity in Carex peat. In 

the acidic surface layers at the study sites the hydrogen 

ions significantly increase or even dominate 

the electric conductivity of peat. For pH 

values lower than 3.5 the conductivity effect due 

to hydrogen ions is at least 10 mS/m (e.g. Kivinen 

1935). At the black schist study sites M2 and M3, 

the effect of bedrock composition on the metal 

(Fe, Ni, Zn) and sulphur concentration of the 

peat as well as the conductivity can be seen in 

the basalmost peat layers (Figs. 13, 15 and 18). 

At the mica schist study site M1 the metal concentrations 

were lower and the change in acidity 

from the about 3.1. in the surface layer to 4.4 in 

the bottom layer is the principal cause of the observed 

reduction in conductivity from 13 mS/m to 

3 mS/m. 

jacent granitic rocks. According to Virtanen et al. 

(1997), the basal peat layer overlying the Pampalo 

gold-arsenic ore deposit at Ilomantsi, in easternmost 

Finland, contains 100 times more arsenic 

than than the average background value for peat 

in the area. Such high values arise from upwards 

migration of metals in groundwater or gaseous



phases from the underlying till. Transport of metals 

in groundwater is influenced by a number of 

factors including capillary flow. At the peatland 

surface, Sphagnum moss absorbs water and nutrients, 

the latter being retained in the moss while the 

water evaporates to the air (Salmi 1955), causing 

slow but continuous upwards migration of water 

from soil to the upper layers of the peat. It has 

also been shown that metal species can be transported 

upwards through bedrock and soils within 

gas bubbles (Kristiansson & Malmqvist 1982). 

Uranium and lead concentrations in peat at 

study sites M1-M3 resemble each other in showing 

higher concentrations of Pb and lower concentrations 

of U in surface layers compared with 

the bottom layers. Uranium concentrations were 

also lower in surface sediments than deeper in the 

profile in organic lake sediments from Lake Kolmisoppi 

at Talvivaara, while lead concentrations 

were higher in surface sediments than deeper in 

the profile (Loukola-Ruskeeniemi et al. 1998). 

The same tendency in peat profiles is probably 

due to the inherent differences between Pb and U 

with respect to redox behaviour and microbiological 

processes. 

At the mica schist study site M1, the concentrations 

of analysed metals and sulphur were lower 

than at the black schist study site M3, with the exception 

of uranium and lead which were present 

at roughly similar concentrations. At the mica 

schist study site, the influence of the bedrock on 

the metal concentrations and conductivity of the 

peat was low, while at the black schist study sites 

the effect of bedrock composition on peat conductivity 

was reflected in elevated concentrations 

of sulphur. A high sulphur concentration lowers 

the pH and increases the conductivity in Carex 

peat. It is notable that the most significant positive 

correlations between metals were recorded 

at study site M2 and the least significant at study 

site M3. At study site M2 there was a highly significant 

positive correlation between all metals 

except for lead and manganese. At study site M3, 

manganese displayed a highly positive correlation 

with iron and sulphur. Copper and uranium were 

also strongly correlated. 

Of the three study sites, the greatest metal and 

ash concentrations were recorded at the black 

schist study site M2, which is situated on the sloping 

peatland, with Ni-rich black schists outcropping 

on the nearby hillside. The average concentrations 

of copper, nickel, zinc and sulphur in the 

peat were many times higher than average values 

reported by Virtanen (2005) from Ostrobothnia, 

western Finland. It seems likely that the outcrops 

of black schist were a source of acid rock drain- 

age during peat formation. A ten-fold ash content 

compared to average values in Finnish peatlands 

provides distinct evidence of acid runoff. The distance 

from the black schist outcrops to study site 

M2 is about 100 m and at the onset of paludification 

there was a difference in elevation of 

more than ten metres. The acidity of peat did not 

change until the 1960s when the peat became drier 

due to drainage of the the peatland, such that sulphur 

(S-ion) became oxidized to SO 4 . The buffering 

capacity of peat was low because of the high 

H 2 SO 4 concentration. 

In addition, peat is always affected by the 

movement of ground water, as the waters carry 

soluble metal ions in the direction of flow. During 

and after transport, the metal concentrations in 

peat pore water may continue to change through 

a variety of chemical reactions. Metal ions have 

remained in the peat because of changes in pH 

or oxidation-reduction state or because they have 

become bound in complexes with peat organic 

compounds, such as humic and fulvic acids (Kapata-Pendias 

1994). Statistically significant correlations 

between Fe, S, Ni, Co, Zn and U were 

observed for peat at study site M2. The pH values 

were lower than the tolerance threshold for peatforming 

plants. Carex peat forms under conditions 

where the pH of the peat layers is typically 

between 4 and 5. Accordingly, the pH of peat at 

study site M2 must also have been of the same 

order of magnitude, as Carex peat had formed in 

the area. Beneath the surface layer of the peat deposits, 

pH values varied between 2.8–3.8. 

Peat acidity at site M2 changed during and after 

pre-mining peatland drainage activity in the 

1960s. Excavations extended in the margins of 

mire down to the bedrock or at least to the basalmost 

layers of glacial till. A variety of chemical 

and microbiological reactions affect the metal 

concentrations in the pore waters in peat. Since 

both the bedrock and till at Talvivaara contain 

abundant sulphides, the surface waters flowing 

in peatland drainage channels reacted with 

sulphide-rich material resulting in acid runoff in 

the nearby streams. A dense network of drainage 

channels also promotes vegetation growth and 

root systems, which in turn enhances the movement 

of water in peatlands because the permeability 

of peat is dependent primarily on the structure 

of the peat and the presence of tree roots and 

debris. Drainage directly improves water runoff 

and movement possibilities. In general, permeability 

is greater in woody peat than in Carex or 

Sphagnum peat, when compared at the same degree 

of humification (Päivänen 1982). 

33



Element concentrations in peat layers result from 

complex interactions between a number of processes. 

Elements and more complex compounds 

are transported from the underlying mineral substrate 

into peat via plant roots in the form of soluble 

ions. The concentrations of soluble ions in peat 

are controlled by several factors, including acidity, 

oxidation conditions, ion exchange capacity, 

and the number of complex compounds. In areas 

such as Talvivaara, characterized by high natural 

sulphur and metal concentrations in bedrock soil, 

capillary water, surface water and ground water 

all contain above average abundances of sulphur 

and metals. Since peat accumulation in the Talvivaara 

area commenced about 10 000 years ago, 

there has been a considerable amount of time for 

metals to precipitate from groundwaters within 

peat. The analysed metals displayed greater concentrations 

in the basalmost peat deposits of 

Carex peat than in the surface layers of Sphagnum-dominated 

peat. Iron-sulphur compounds 

in peat evidently cause a lowering of pH at high 

concentrations and thereby lead to an increase in 

conductivity. The effect on pH levels becomes apparent 

when the concentrations of both iron and 

sulphur are approximately 20 000 mg/kg or 2 000 

g/peatland-m 3 . 

At the black schist study sites M2 and M3, the 

elements showing the greatest increase in concentration 

with depth were nickel, iron, sulphur and 

zinc. At the mica schist study site M1, the concentrations 

of copper, nickel and sulphur increased 

as a function of depth. Variations in concentrations 

were caused by fluctuations in ground water 

level as well as changes in the movement and accumulation 

of the elements. The concentrations 

of zinc, manganese and lead were greatest at the 

peatland surface, immediately below the surface 

layer of peat. 

Of the three Talvivaara study sites, the highest 

metal and ash concentrations were recorded at the 

black schist study site M2. Instead of attributing 

We thank Ale Grundström for assistance during 

fieldwork and for many inspiring discussions 

and valuable comments on the manuscript, and 

numerous colleagues at the Geological Survey of 

34 

7 CONCLUSIONS 

ACKNOwLEDGEMENTS 

this to the influence of Ni-rich ground waters, it 

seems more likely that there has been acid rock 

drainage from Ni-rich black schists on the adjacent 

hillside throughout the entire history of peat 

formation. In addition, peatland drainage activities 

in the 1960s resulted in acid runoff wherever 

excavation penetrated to the underlying Ni-rich 

bedrock or Ni-rich glacial till. At this study site 

metals were precipitated in the peat deposits. 

Therefore, we can see a natural analogue for the 

method of remediation of mining environments 

with peat at Talvivaara. 

Under anaerobic conditions, such as those 

prevailing in peat, sulphur mainly occurs as sulphides. 

Sulphides are oxidized to soluble and 

mobile sulphates when conditions change from 

anaerobic to aerobic. Peatland drainage leads to 

aerobic conditions and consequently oxidation of 

sulphides to sulphates. Leaching of sulphur from 

peat may in turn cause environmental problems 

such as acid runoff. The high sulphur content in 

peatlands in black schist areas and the consequent 

low pH values lead to high electrical conductivity 

levels, especially in the sedge-dominated bottom 

layer. 

Except for the topmost Sphagnum-dominated 

layer, the sulphur concentrations in the layer underlying 

the surficial peat at each of the study sites 

exceeded the upper limit of 0.50% of dry mass, 

which is the highest value class for energy peat 

in northern Europe (Nordtest Innovation Center 

2006). The sulphur content of peat has a significant 

impact on the suitability of peatland for 

commercial peat production. This is mainly due 

to the corrosive effects on power plant equipment, 

but the evaluation and minimization of sulphur 

emissions resulting from peat incineration is also 

important (Virtanen 2005, Herranen 2010). When 

planning peat production near sulphide-rich bedrock 

and/or soil, the quality of peat should be 

studied and sulphur-rich peat should be excluded 

from production. 

Finland for their co-operation. We are particularly 

grateful to Kimmo Virtanen for his comments 

and Peter Sorjonen-Ward for checking the English 

of the manuscript.



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www.gtk.fi 

info@gtk.fi 

Three peat study sites representing different bedrock types 

and hydrological conditions were sampled in the Talvivaara 

area in 2005, before the large-scale mining activities began in 

2008. The concentrations of Co, Cu, Fe, Mn, Ni, U, Zn and S 

and conductivity were lower in peat at a study site on mica 

schist bedrock than at two study sites underlain by black 

schists hosting the Talvivaara Ni-Cu-Zn-Co deposit. Black 

schist refers to a graphite and sulphide rich metasedimentary 

rock. It seems likely that hydrological conditions at one sloping 

peatland site underlain by black schist have been conducive 

to acid rock drainage, production and transport of acidic 

surface waters with Ni-Cu-Zn-Co- rich suspension from 

adjacent black schist outcrops and glacial till throughout the 

entire history of peat accumulation. The peat layer evidently 

functioned in the same way as peat filters in the remediation 

of acid mine drainage in present-day mine environments, i.e. 

metals were retained in the peat. The acidity of peat changed 

beneath the surface peat layer in the 1960s when the peat 

became drier due to drainage of the peatland, and sulphur 

oxidized to SO 4 . We conclude that in sulphide-rich terrain, 

sulphur concentrations in peat can be high, and leaching of 

sulphur from peat to surface waters during and after peatland 

drainage activities may lead to environmental problems. 

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