Partitioning of transition metals in oxidised and reduced zones of sulphide-bearing fine-grained sediments

doi:10.1016/S0883-2927(97)00093-0

Applied Geochemistry

Volume 13, Issue 5, July 1998, Pages 607-617

https://doi.org/10.1016/S0883-2927(97)00093-0 Get rights and content

Abstract

Distribution and forms of transition metals (Ti, Zn, Ni, Co, Mn, Fe, Cu, V and Cr) were investigated in oxidised, partly oxidised and reduced zones of sulphide-bearing fine-grained sediments located in the coastal areas of western Finland. Samples for the analysis and study of vertical distribution of elements were taken from each vertical 10 cm section in pits ranging in depth between 2 and 3 metres, while bulk samples for characterisation of species and forms of metals were taken from 3 zones in each pit: the acid sulphate soil (characterised by acid and oxidising conditions), transition zone (characterised by a steep pH gradient and partly oxidising conditions) and the reduced zone (pH >6). The former samples were digested in aqua regia (3:1:2 HCl:HNO₃:H₂O), while the latter were digested in aqua regia and hot concentrated acids (HClO₄–HNO₃–HCl–HF) and were subjected to extractions with acid ammonium acetate, H₂O₂ and acid ammonium oxalate. Each leachate was analysed for metals with ICP–AES.

The vertical variation in the concentrations of Ti were small at all the studied sites indicating that the sediments are homogeneous and that the total losses of other elements from the soil profiles (acid sulphate soil+transition zone) are not extensive. Field observations, extractions with ammonium oxalate, and concentration–variation patterns indicated that Fe-oxide is largely precipitated and retained also in these acid soils. There are, however, indications of redistribution of Fe within the soil profiles. The results also demonstrated that Mn, Ni, Zn, Co and Cu have been lost in considerable amounts from the acid sulphate soils. However, whereas Mn in general has been lost throughout the soil profile, part of the Zn, Ni and Co released in the acid sulphate soils have migrated downward and been reimmobilised in the transition zone immediately above the reduced zone. Also Cu has been lost from the acid sulphate soil, but generally in smaller proportions than Mn, Zn, Ni and Co. Dissolved metal sulphides seem to be major sources of the mobilised metal fractions. A main part of the V and Cr in the sediments are associated with weathering-resistant minerals. These metals are therefore, like Ti, only to a limited extent mobilised by the oxidation of the sulphide-bearing sediments.

Introduction

The extent of metal–sulphide oxidation, the H⁺ buffering properties of the sediment/soil material and the amounts of easily mobilised chemical elements are factors that control the extent of geochemical dispersion and environmental impact caused by the oxidation of sulphide-bearing fine-grained sediments. The mechanisms of the oxidation reactions of reduced S compounds have been studied in detail (Wiklander et al., 1950; Lowson, 1982; Morse et al., 1987), and oxidation experiments in laboratory and field studies have shown that severe acidity commonly develops rapidly when these type of sediments are exposed to atmospheric O₂ (Wiklander et al., 1950; Purokoski, 1958; Brinkman and Pons, 1973; Dent, 1980; Pons et al., 1982; Hartikainen and Yli-Halla, 1986). The H⁺ buffering properties, which are related largely to the contents of carbonate material, easily weathered silicate minerals and exchangeable “base” cations (van Breemen, 1973; Pons et al., 1982), have been determined in many sediments and soils. However, the concentration levels and behaviour of various trace elements in these environments are not known in detail (van Breemen, 1993).

The general objective of this investigation was to increase our knowledge concerning the solubilisation and redistribution of first-row transition metals (Ti, Co, Ni, Zn, Cu, Mn, V, Cr and Fe) caused by the oxidation of sulphide-bearing fine-grained sediments. The specific aims were to (1) compare the concentration levels of metals in oxidised, partly oxidised and reduced zones, (2) determine the relative proportions of metals extracted with weak and strong chemical reagents in the various zones of the sediments, (3) identify and quantify the factors controlling the mobility of metals in these environments and (4) estimate the relative losses of metals from the oxidised zones.

The sulphide-bearing fine-grained sediments located in the Quark area, western Finland, were selected for this study since the uppermost layers of most of these sediments are subjected to strong oxidation and weathering due to extensive artificial drainage activities initiated in the 1950s. Investigation of vertical profiles through these soils and sediments can, as a consequence, provide us with valuable information concerning the behavior of metals in sulphide-bearing fine-grained sediments exposed to atmospheric O₂.

Section snippets

Geology of the study area

In the Quark area, western Finland (Fig. 1), the topography is very subdued and the surface inclination towards the sea on average only some 1.5 m/km. Since the region was below the thickest parts (>3 km) of the Pleistocene continental ice sheet, which reached its maximum extent some 2×10⁴ a ago, isostatic land uplift is a characteristic feature of the area (Atlas of Finland, 1990; Donner, 1995). Shortly after the retreat of the ice cover (approximately 10⁴ a B.P.) the uplift was very fast but

Site descriptions

The site locations (n=5; A–E) of the fine-grained sediments and the associated soils studied are shown in Fig. 1. In the ground-water zone (located at depths greater than 100–180 cm), where the O₂ supply is limited, the sediments were dark grey to black as a result of dispersed fine-grained amorphous and poorly crystalline Fe mono-sulphides. The smell of H₂S was evident in this zone. Above the ground-water table, where acid sulphate soils have developed, the soil material had an orange–brown

Sampling

Samples of soil and sediment were taken from each vertical 10 cm section, except from the cultivated topsoil (uppermost 10–50 cm of a profile), in the pits at sites A–E ranging in depths between 2 m and 3 m. A 9 ml portion of sample material was collected in a plastic tube and was stirred with 15 ml of deionised water for measurement of pH, and about 200g was sampled for chemical analyses. The samples for chemical analysis were subsequently dried in an oven at 50°C.

A bulk sample (approximately

Results and discussion

The investigation of the vertical variation of metals in the profiles is based on the aqua regia extractable fractions of the metals. However, in 15 soil/sediment samples (one sample from each zone in each studied profile) the median ratio of the amount extracted in aqua regia to the total concentration (see above) are 0.8–1.0 for Cu, Co, Zn, Ni, Fe, Mn and Cr, while they are approximately 0.5 for Ti and V. It can, therefore, be assumed that the variation patterns of at least the former 7

CONCLUSIONS

The results presented in this study show that Mn, Zn, Ni, Co and Cu are released and mobilised in large amounts when sulphide-bearing fine-grained sediments are exposed to atmospheric O₂. However, while Mn in general is lost throughout the soil profiles developed on these sediments, part of the Zn, Ni and Co released in the acid sulphate soil is transported downward and reprecipitated in the zone immediately above the ground-water table (transition zone). The behaviour of Cu is less regular,

Acknowledgements

The author wishes to thank Professor Alf Björklund for practical advice and comments on the manuscript, and the staff of the Chemical Laboratory of the Geological Survey of Finland for the chemical analysis. The study was financed by the Academy of Finland and the Åbo Akademi University.
Editorial handling:—Dr Don Runnells.

References (53)

M. Åström et al.
Impact of acid sulphate soils on stream water geochemistry in western Finland
J. Geochem. Explor.
(1995)
T.T. Chao
Use of partial dissolution techniques in geochemical exploration
J. Geochem. Explor.
(1984)
K. Lax et al.
Wide-spaced sampling of humus in Fennoscandia
J. of Geochem. Explor.
(1995)
J.W. Morse et al.
Adsorption and coprecipitation of divalent metals with mackinawite (FeS)
Geochim. Cosmochim. Acta
(1993)
J.W. Morse et al.
The chemistry of the hydrogen sulphide and iron sulphide systems in natural waters
Earth-Sci. Reviews
(1987)
J.W. Murray
The interaction of metal ions at the manganese dioxide-solution interface
Geochim. Cosmochim. Acta
(1975)
J.W. Murray
The interaction of cobalt with hydrous manganese dioxide
Geochim. Cosmochim. Acta
(1975)
I. Öborn
Properties and classification of some acid sulphate soils in Sweden
Geoderma
(1989)
M.A. Rashid
Absorption of metals on sedimentary and peat humic acids
Chem. Geol.
(1974)
H. Sandström
Selective sequential dissolution of organic-rich stream sediments from Talvivaara
Finland. J. Geochem. Explor.
(1984)

F. Sondag

Selective extraction procedures applied to geochemical prospecting in an area contaminated by old mine workings

J. Geochem. Explor

(1981)

E. Tipping et al.

A unifying model of cation binding by humic substances

Geochim. Cosmochim. Acta

(1992)

B. Wehrli et al.

Vanadyl in natural waters: adsorption and hydrolysis promote oxygenation

Geochim. Cosmochim. Acta

(1989)

Åström M. (1996). Geochemistry, chemical reactivity and extent of leaching of sulphide-bearing fine-grained sediments...

M. Åström et al.

Hydrogeochemistry of a stream draining sulphide-bearing postglacial sediments in Finland

Water Air Soil Pollut.

(1996)

Åström M. and Björklund A. (1997) Geochemistry and acidity of sulphide-bearing sediments of western Finland. Environ....

Åström M. and Åström J. (1997) Geochemistry of stream water in a catchment in Finland affected by sulphidic fine...

Atlas of Finland (1990) Geology, Folio 123–126. National Board of Survey and Geographical Society of Finland,...

P.R. Anderson et al.

Distribution coefficients of Cd, Co, Ni and Zn in soils

J. Soil Sci.

(1988)

H.P. Blume et al.

Genetic evaluation of profile distribution of Al, Fe and Mn oxides

Soil Sci. Soc. Am. Proc

(1969)

van Breemen N. (1973) Soil forming processes in acid sulphate soils. In Proc. Int. Symp. on Acid Sulphate Soils (ed. H....

van Breemen N. (1993) Environmental aspects of acid sulphate soils. In Selected Papers of the Ho Chi Minh City...

N. van Breemen et al.

Translocation of iron in acid sulphate soils: soil morphology, and the chemistry and mineralogy of iron in a chronosequence of acid sulphate soils

Soil Sci. Soc. Amer. Proc.

(1975)

Brinkman R. and Pons L. J. (1973) Recognition and prediction of acid sulphate soil conditions. In Proc. Int. Symp. on...

Diemont W. H., Pons L. J. and Dent D. L. (1993) Standard profiles of acid sulphate soils. In Selected Papers of the Ho...

D. Dent

Acid sulphate soils: morphology and prediction

J. Soil Sci.

(1980)

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Partitioning of transition metals in oxidised and reduced zones of sulphide-bearing fine-grained sediments

Abstract

Introduction

Section snippets

Geology of the study area

Site descriptions

Sampling

Results and discussion

CONCLUSIONS

Acknowledgements

J. Geochem. Explor.

J. Geochem. Explor.

J. of Geochem. Explor.

Geochim. Cosmochim. Acta

Earth-Sci. Reviews

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geoderma

Chem. Geol.

Finland. J. Geochem. Explor.

J. Geochem. Explor

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Hydrogeochemistry of a stream draining sulphide-bearing postglacial sediments in Finland

Water Air Soil Pollut.

Distribution coefficients of Cd, Co, Ni and Zn in soils

J. Soil Sci.

Genetic evaluation of profile distribution of Al, Fe and Mn oxides

Soil Sci. Soc. Am. Proc

Translocation of iron in acid sulphate soils: soil morphology, and the chemistry and mineralogy of iron in a chronosequence of acid sulphate soils

Soil Sci. Soc. Amer. Proc.

Acid sulphate soils: morphology and prediction

J. Soil Sci.