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Liu, J.-l., Yao, J., Wang, F., Ni, W., Liu, X.-y., Sunahara, G., . . . Li, Z.-f. (2018). China's most typical nonferrous organic-metal facilities own specific microbial communities. Scientific Reports, 8(1), Article ID 12570.
Open this publication in new window or tab >>China's most typical nonferrous organic-metal facilities own specific microbial communities
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 12570Article in journal (Refereed) Published
Abstract [en]

The diversity and function of microorganisms have yet to be explored at non-ferrous metal mining facilities (NMMFs), which are the world's largest and potentially most toxic sources of co-existing metal(loid)s and flotation reagents (FRs). The diversity and inferred functions of different bacterial communities inhabiting two types of sites (active and abandoned) in Guangxi province (China) were investigated for the first time. Here we show that the structure and diversity of bacteria correlated with the types of mine sites, metal(loid)s, and FRs concentrations; and best correlated with the combination of pH, Cu, Pb, and Mn. Combined microbial coenobium may play a pivotal role in NMMFs microbial life. Arenimonas, specific in active mine sites and an acidophilic bacterium, carries functions able to cope with the extreme conditions, whereas Latescibacteria specific in abandoned sites can degrade organics. Such a bacterial consortium provides new insights to develop cost-effective remediation strategies of co-contaminated sites that currently remain intractable for bioremediation.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Geochemistry
Research subject
Applied Geochemistry
Identifiers
urn:nbn:se:ltu:diva-70592 (URN)10.1038/s41598-018-30519-1 (DOI)000442387900034 ()30135589 (PubMedID)2-s2.0-85052145242 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-27 (andbra)

Available from: 2018-08-27 Created: 2018-08-27 Last updated: 2018-09-10Bibliographically approved
Karlsson, T., Räisänen, M. L., Lehtonen, M. & Alakangas, L. (2018). Comparison of static and mineralogical ARD prediction methods in the Nordic environment. Environmental Monitoring & Assessment, 190(12), Article ID 719.
Open this publication in new window or tab >>Comparison of static and mineralogical ARD prediction methods in the Nordic environment
2018 (English)In: Environmental Monitoring & Assessment, ISSN 0167-6369, E-ISSN 1573-2959, Vol. 190, no 12, article id 719Article in journal (Refereed) Published
Abstract [en]

Acid rock drainage (ARD) is a major problem related to the management of mining wastes, especially concerning deposits containing sulphide minerals. Commonly used tests for ARD prediction include acid–base accounting (ABA) tests and the net acid generation (NAG) test. Since drainage quality largely depends on the ratio and quality of acid-producing and neutralising minerals, mineralogical calculations could also be used for ARD prediction. In this study, several Finnish waste rock sites were investigated and the performance of different static ARD test methods was evaluated and compared. At the target mine sites, pyrrhotite was the main mineral contributing to acid production (AP). Silicate minerals were the main contributors to the neutralisation potential (NP) at 60% of the investigated mine sites. Since silicate minerals appear to have a significant role in ARD generation at Finnish mine waste sites, the behaviour of these minerals should be more thoroughly investigated, especially in relation to the acid produced by pyrrhotite oxidation. In general, the NP of silicate minerals appears to be underestimated by laboratory measurements. For example, in the NAG test, the slower-reacting NP-contributing minerals might require a longer time to react than is specified in the currently used method. The results suggest that ARD prediction based on SEM mineralogical calculations is at least as accurate as the commonly used static laboratory methods.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
ABA test, NAG test, SEM, Waste rock, Risk assessment
National Category
Geochemistry
Research subject
Applied Geochemistry
Identifiers
urn:nbn:se:ltu:diva-71593 (URN)10.1007/s10661-018-7096-2 (DOI)000450098200002 ()30426238 (PubMedID)2-s2.0-85056501281 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-15 (johcin)

Available from: 2018-11-15 Created: 2018-11-15 Last updated: 2018-12-04Bibliographically approved
Hällström, L., Alakangas, L. & Martinsson, O. (2018). Geochemical characterization of W, Cu and F skarn tailings at Yxsjöberg, Sweden. Journal of Geochemical Exploration, 194, 266-279
Open this publication in new window or tab >>Geochemical characterization of W, Cu and F skarn tailings at Yxsjöberg, Sweden
2018 (English)In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 194, p. 266-279Article in journal (Refereed) Published
Abstract [en]

Little attention has been paid to tailings from skarn ore deposits and their environmental impact, even though they can contain elevated concentrations of elements of potential concern together with sulfides and fluorite. Historical skarn tailings at Yxsjöberg, Sweden, containing e.g. Be, Bi, Cu, F, Sn, S, W, and Zn were geochemically characterized as a first step to evaluate the environmental impact and the potential to re-mine the tailings. The tailings were deposited between 1897 and 1963 in the Smaltjärnen Repository without dams or a complete cover, and have been in contact with the atmosphere for >30 years. Four vertical cores throughout the tailings were taken and divided into 134 subsamples, which were analyzed for total concentrations and paste pH. Selected samples from different depths were mineralogically characterized using optical microscopy, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), Raman vibrational spectroscopy, and X-ray diffraction (XRD). Minerals, hand-picked from drilled rock cores, were analyzed for the element content, and a modified Element to Mineral Conversion (EMC) that pinpoints the quantitative distribution of elements between the minerals in the tailings was carried out. The average concentrations of Be, Bi, Cu, Sn, Zn, W, F and S in the tailings were 284, 495, 946, 559, 301, and 960 ppm, and 1.9 and 1.2 wt%, respectively. The tailings has reached a late stage development due to pyrrhotite oxidation resulting in low pH (<4) in the uppermost tailings, and formations of secondary minerals such as gypsum, hydrous ferric oxides (HFO) and orthogonal calcite. Secondary pyrite and magnetite, formed from monoclinic pyrrhotite was detected, and different weathering rates of secondary pyrite, hexagonal and monoclinic pyrrhotite was indicated, with secondary pyrite as the most stable and monoclinic pyrrhotite as the least. The rare and easily-weathered mineral danalite (Fe4Be3(SiO4)3S) was found in the drilled rock cores and by XRD in the tailings. However, the mineral could not be found by optical microscopy or SEM-EDS. This suggests that the mineral has been weathered to a great extent, which poses a high risk of releasing elements of potential concern to the groundwater since danalite contains approximately 40% of the total Be and Zn concentrations in the tailings. Fluorine was mainly found in fluorite, Cu in chalcopyrite, and Bi in bismuthinite; which all showed signs of weathering in acidic condition in the uppermost part, subsequent with decreased concentrations, followed by accumulation peaks deeper down in the tailings correlated with Al. Tungsten was mainly found in scheelite; most grains were unweathered, but a few grains had altered rims or HFO on the mineral surfaces. Tin was mainly found in ferrohornblende, hedenbergite and grossular. Beryllium, Cu, F, and Zn has high potential to be released to the surrounding environment from the Smaltjärnen Repository, while W, Bi and Sn are relatively stable in the tailings. Most of the scheelite is intact and re-mining could, therefore, be a suitable remediation method that would both reduce the environmental impact and simultaneously support the supply of critical raw materials in the EU.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Geology Geochemistry
Research subject
Applied Geochemistry; Ore Geology
Identifiers
urn:nbn:se:ltu:diva-70827 (URN)10.1016/j.gexplo.2018.09.001 (DOI)000447940000021 ()2-s2.0-85053199965 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-09-21 (svasva)

Available from: 2018-09-11 Created: 2018-09-11 Last updated: 2018-11-15Bibliographically approved
Salifu, M., Aiglsperger, T., Hällström, L., Martinsson, O., Billström, K., Ingri, J., . . . Alakangas, L. (2018). Strontium (87Sr/86Sr) isotopes: A tracer for geochemical processes in mineralogically-complex mine wastes. Applied Geochemistry, 99, 42-54
Open this publication in new window or tab >>Strontium (87Sr/86Sr) isotopes: A tracer for geochemical processes in mineralogically-complex mine wastes
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2018 (English)In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 99, p. 42-54Article in journal (Refereed) Published
Abstract [en]

Interpretation of geochemical data based primarily on elemental concentrations often lead to ambiguous results due to multiple potential sources including mineral weathering, atmospheric input, biological cycling, mineral precipitation and exchange processes. The 87Sr/86Sr ratio is however not fractionated by these processes. In this study, Sr isotope (87Sr/86Sr) ratios have been coupled with chemical data of Sr and Rb-bearing minerals, tailings and leachates (water-soluble) to gain insight into the geochemical processes occurring within the Yxsjöberg Cu-W mine tailings, Sweden. The tailings have been exposed to oxidizing conditions resulting in three geochemical zones namely (i) oxidized, (ii) transition and (iii) unoxidized zones. Leachates from the oxidized zone are acidic (pH = 3.6–4.5) and contain elevated concentrations of metals (e.g. Fe, Cu and Zn) and SO4. The low pH has also led to subsequent weathering of most silicates, releasing Al, Ca, Mg and Na into solution. The 87Sr/86Sr ratio in the tailings ranges from 0.84787 to 1.26640 in the oxidized zone, 0.92660–1.06788 in the transition zone, whilst the unoxidized zone has values between 0.76452 and 1.05169. For the leachates, the 87Sr/86Sr ratio ranges from 2.44479 to 5.87552 in the oxidized zone, 1.37404–1.68844 in the transition zone and 1.03697–2.16340 in the unoxidized zone. Mixing (between mineral weathering and atmospheric sources) was identified as the major process regulating the Sr composition of the tailings and leachates. The highly radiogenic signatures of the leachates in the oxidized zone suggests weathering of biotite, K-feldspar and muscovite. Despite the very radiogenic signatures in the oxidized zone, increments in Ca/K ratios, Be, Ce, Tl, Al, Fe and SO4 concentrations in the water-soluble phase were recorded in its lower parts which suggests the dissolution of amphibole, pyroxene, plagioclase, fluorite, gypsum, Al and Fe –(oxy) hydroxides as well as cation exchange by clay minerals. Presence of clay minerals has led to the partial retainment of radiogenic 87Sr/86Sr resulting in increased 87Sr/86Sr in the solid tailings material at these depths. The 87Sr/86Sr ratios of the water-soluble phase in the transition zone is similar to that of helvine and could indicate its dissolution. In the upper part of the oxidized zone, the 87Sr/86Sr ratios and trends of Be, Ca, SO4, Tl and Zn in the water-soluble phase suggest the dissolution of gypsum which precipitated from a leachate with the isotopic signature of helvine. In the lower part of the unoxidized zone, elevated concentrations of W were recorded suggesting scheelite weathering. But the 87Sr/86Sr ratios are higher than that expected from dissolution of scheelite and indicates additional processes. Possible sources include biotite weathering and groundwater. This study reveals that when interpreting geochemical processes in mine waste environments, 87Sr/86Sr should be considered in addition to chemical constituents, as this isotopic tracer offers better insights into discriminating between different solute sources.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Strontium isotopes, Silicate weathering, Yxsjöberg, Skarn mine tailings, Water-soluble
National Category
Geochemistry Geology
Research subject
Applied Geochemistry; Ore Geology
Identifiers
urn:nbn:se:ltu:diva-71501 (URN)10.1016/j.apgeochem.2018.10.022 (DOI)2-s2.0-85055999912 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-07 (johcin)

Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2018-12-10Bibliographically approved
Hamberg, R., Maurice, C. & Alakangas, L. (2018). The formation of unsaturated zones within cemented paste backfill mixtures: Effects on the release of copper, nickel, and zinc. Environmental science and pollution research international, 25(21), 20809-20822
Open this publication in new window or tab >>The formation of unsaturated zones within cemented paste backfill mixtures: Effects on the release of copper, nickel, and zinc
2018 (English)In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 25, no 21, p. 20809-20822Article in journal (Refereed) Published
Abstract [en]

Flooding of cemented paste backfill (CPB) filled mine workings is, commonly, a slow process and could lead to the formation of unsaturated zones within the CPB-fillings. This facilitates the oxidation of sulfide minerals, and thereby increases the risk of trace-metal leaching. Pyrrhotitic tailings from a gold mine (CT), containing elevated concentrations of Ni, Cu and Zn, were mixed with cement and/or fly ash (1-3 wt. %) to form CT-CPB-mixtures. Pyrrhotite oxidation progressed more extensively during unsaturated conditions, where acidity resulted in dissolution of the Ni, Cu, and Zn associated with amorphous Fe-precipitates and/or cementitious phases. The establishment of acidic, unsaturated conditions in CT-CBP:s with low fractions (1 wt. %) of binders increased the Cu-release (to be higher than that from CT), owing to the dissolution of Cu-associated amorphous Fe-precipitates. In CT-CPB:s with relatively high proportions of binder, acidity from pyrrhotite oxidation was buffered to a greater extent. At this stage, Zn-leaching increased due the occurrence of fly ash-specific Zn-species soluble in alkaline conditions. Irrespective of binder proportion and water saturation level, the Ni- and Zn-release were lower, compared to that in CT. Fractions of Ni, Zn, and Cu associated with acid-soluble phases or amorphous Fe-precipitates, susceptible to remobilization under acidic conditions, increased in tandem with binder fractions. Pyrrhotite oxidation occurred irrespective of the water saturation level in the CPB-mixtures. That in turn, poses an environmental risk, whereas a substantial proportion of Ni, Cu and Zn were associated with acid-soluble phases.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Tailings management, cement, trace metal leaching
National Category
Earth and Related Environmental Sciences
Research subject
Applied Geochemistry
Identifiers
urn:nbn:se:ltu:diva-68435 (URN)10.1007/s11356-018-2222-9 (DOI)000438830900052 ()29756187 (PubMedID)
Note

Validerad;2018;Nivå 2;2018-08-07 (andbra)

Available from: 2018-04-20 Created: 2018-04-20 Last updated: 2018-11-15Bibliographically approved
Hamberg, R., Maurice, C. & Alakangas, L. (2017). Lowering the water saturation level in cemented paste backfill mixtures: Effect on the release of arsenic. Minerals Engineering, 112, 84-91
Open this publication in new window or tab >>Lowering the water saturation level in cemented paste backfill mixtures: Effect on the release of arsenic
2017 (English)In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 112, p. 84-91Article in journal (Refereed) Published
Abstract [en]

The Cemented Paste Backfill (CPB) method allows the mixing of dewatered tailings slurries with cementitious binders to backfill excavated underground workings. After mine closure, CPB workings are permanently flooded by rising groundwater. This flooding is considered beneficial for reducing the risk of acid generation associated with CPB containing sulphide minerals. In general, CPB workings are slowly flooded and the process may lead to regions with a low degree of water saturation to form within the CPB. This in turn, may increase oxygen ingress in the CPB, thereby prolonging oxidation of the minerals. To investigate the environmental impact of this oxidation, tailings containing elevated concentrations of arsenic (As) and pyrrhotite were handled via CPB. In this study, CPB mixtures containing 1–3 wt.% of cementitious binders and tailings was studied. The water saturation level in the CPB-mixtures was lowered as curing time extended. In mimicked flooded conditions, the mobility of As in the CPB mixtures was correlated with As-bearing cementitious phases that are sensitive to a reduction in the pH. In CPB-mixtures with lower proportions of binders, cementitious As-phases dissolved while the water saturation level decreased to form more stable As-phases. Increasing binder fractions, most of the cementitious As-phases persisted in the CPB while water saturation levels were lowered and release of As increased. Regardless of curing conditions, managing these tailings via the CPB method yielded increased mobility of As compared with that in the unmodified tailings; this resulted possibly from the formation of less acid-tolerant As species.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Geochemistry
Research subject
Applied Geochemistry
Identifiers
urn:nbn:se:ltu:diva-65077 (URN)10.1016/j.mineng.2017.05.005 (DOI)000410868200011 ()2-s2.0-85026233469 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-08-15 (andbra)

Available from: 2017-08-15 Created: 2017-08-15 Last updated: 2018-07-10Bibliographically approved
Filcenco-Olteanu, A., Alakangas, L., Fiuza, A., Zlǎgnean, M. & Tomuş, N. (2017). Physical chemical characterization of historical mining waste and ARD prediction tests. Paper presented at Mineral Engineering Conference, MEC 2017, Wisla, Poland, 20-23 September 2017. E3S Web of Conferences, 18(4), Article ID 01031.
Open this publication in new window or tab >>Physical chemical characterization of historical mining waste and ARD prediction tests
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2017 (English)In: E3S Web of Conferences, E-ISSN 2267-1242, Vol. 18, no 4, article id 01031Article in journal (Refereed) Published
Abstract [en]

There are thousands of historical mine tailings and metallurgical residues present on inactive metal mining sites which have been abandoned. However, the potential release of dissolved metals, acidity, or suspended particulates from mine-waste dumps can be a serious and long-lasting problem. A variety of environmental impacts may occur at this abandoned mine sites and leading the list is acid generation, which is one of the main problems from metal mining. The objective of the present study was to characterize and evaluate the Romanian historical tailing of Sasar-Red Valley, near Baia Mare. This involved physical and chemical characterization of the materials and its acid generating potential. Sasar tailing impoundment contains 8.5 million m3 of tailings and occupies an area of 32.5 hectares. Tailings samples were collected from different depths in three sampling points, and characterized by grain size, chemical elements concentration, elements distribution of elements in depth, paste pH, acid-base account and net acid generation tests. Acid base accounting (ABA) tests in conjunction with net acid generation (NAG) tests classified the samples into the category of 'potentially acid generating'. This paper presents a synthesis of works performed in the Improve Resource Efficiency and Minimize Environmental Footprint (REMinE) project.

Place, publisher, year, edition, pages
EDP Sciences, 2017
National Category
Geochemistry
Research subject
Applied Geochemistry
Identifiers
urn:nbn:se:ltu:diva-66315 (URN)10.1051/e3sconf/201712301031 (DOI)2-s2.0-85031704706 (Scopus ID)
Conference
Mineral Engineering Conference, MEC 2017, Wisla, Poland, 20-23 September 2017
Note

Konferensartikel i tidskrift

Available from: 2017-10-30 Created: 2017-10-30 Last updated: 2017-11-24Bibliographically approved
Nyström, E., Kaasalainen, H. & Alakangas, L. (2017). Prevention of Sulfide Oxidation in Waste Rock using By-products and Industrial Remnants: a Suitability Study. In: Wolkersdorfer, C.; Sartz, L.; Sillanpää, M. & Häkkinen, A (Ed.), Mine Water & Circular Economy: A Green Congress. Paper presented at 13th International Mine Water Association Congress – “Mine Water & Circular Economy – A Green Congress”, Lappeenranta, Finland, 25-30 June 2017 (pp. 1170-1178). , 2
Open this publication in new window or tab >>Prevention of Sulfide Oxidation in Waste Rock using By-products and Industrial Remnants: a Suitability Study
2017 (English)In: Mine Water & Circular Economy: A Green Congress / [ed] Wolkersdorfer, C.; Sartz, L.; Sillanpää, M. & Häkkinen, A, 2017, Vol. 2, p. 1170-1178Conference paper, Published paper (Refereed)
Abstract [en]

Prevention and mitigation of acid rock drainage from mining are decisive for limiting environmental impact. Five by-products and industrial remnants (lime kiln dust, blast furnace slag, granulated blast furnace slag, cement kiln dust and fly ash) were investigated for their suitability to prevent acidity and metal(loid)s during leaching from highly sulfidic (50wt%, sulfide) waste rock in small scale laboratory test cells. Variations in pH and electrical conductivity in leachate allowed differentiation between the different materials. Lime kiln dust (5wt%) and fly ash (1 and 2.5wt%) were observed to be the most suitable materials to prevent acidity and metal(loid)s leaching.

National Category
Geochemistry
Research subject
Applied Geochemistry
Identifiers
urn:nbn:se:ltu:diva-66362 (URN)
Conference
13th International Mine Water Association Congress – “Mine Water & Circular Economy – A Green Congress”, Lappeenranta, Finland, 25-30 June 2017
Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2017-11-24Bibliographically approved
Nason, P., Jia, Y., Maurice, C., Alakangas, L. & Öhlander, B. (2016). Biodegradation of Biosolids Under Aerobic Conditions: Implications for Cover Materials for Sulfide Mine Tailings Remediation (ed.). Mine Water and the Environment, 35(3), 273-282
Open this publication in new window or tab >>Biodegradation of Biosolids Under Aerobic Conditions: Implications for Cover Materials for Sulfide Mine Tailings Remediation
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2016 (English)In: Mine Water and the Environment, ISSN 1025-9112, E-ISSN 1616-1068, Vol. 35, no 3, p. 273-282Article in journal (Refereed) Published
Abstract [en]

Sewage sludge residue (biosolids) was investigated for its potential as a long-term tailings cover. Biosolids may prevent oxygen diffusion into underlying sulfide tailings through microbial aerobic biodegradation of organic matter. Biosolids were investigated at laboratory-, pilot-, and field-scale using analysis of total organic matter (TOM) mass reduction and O2, CO2, CH4 concentrations to quantify the biodegradation rate. A 156-day, open microcosm experiment, in which the loss of biosolids mass over time at differing temperatures, mimicking ambient (20–22 °C), mesophilic (34 °C), and thermophilic (50 °C) conditions, indicated that TOM biodegradation was best in the mesophilic temperature range, with 14.8, 27.2, and 26.7 % mass depletion at ambient, mesophilic, and thermophilic conditions, respectively. The data was correlated to field-scale data that evaluated biodegradation rates via decreasing O2 and increasing CO2 concentrations. Field biodegradation rates were less than laboratory rates because lower mean annual temperatures (0.6–0.7 °C) diminished microbial activity. A calibrated model indicates that 20 % of a field application of biosolids will degrade within 2 years. However, the rate declines with time due to exhaustion of the most readily degradable organic fraction. If biodegradation cannot be maintained, the long-term effectiveness of biosolids as a covering material for mine tailings remains a concern.

National Category
Geochemistry
Research subject
Applied Geology
Identifiers
urn:nbn:se:ltu:diva-15882 (URN)10.1007/s10230-015-0339-3 (DOI)000382193900002 ()2-s2.0-84928624256 (Scopus ID)f734105d-fe2c-485f-8869-7e75ca81458c (Local ID)f734105d-fe2c-485f-8869-7e75ca81458c (Archive number)f734105d-fe2c-485f-8869-7e75ca81458c (OAI)
Note

Validerad; 2016; Nivå 2; 2016-10-18 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Zhang, W., Alakangas, L., Wei, Z. & Long, J. (2016). Geochemical evaluation of heavy metal migration in Pb-Zn tailings covered by different topsoils (ed.). Paper presented at . Journal of Geochemical Exploration, 165, 134-142
Open this publication in new window or tab >>Geochemical evaluation of heavy metal migration in Pb-Zn tailings covered by different topsoils
2016 (English)In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 165, p. 134-142Article in journal (Refereed) Published
Abstract [en]

Heavy metal migration was evaluated in Pb-Zn tailings covered by different topsoil constructions. The four topsoil constructions each had different interlayers: one with direct topsoiling above the tailings (CT); the second had a limestone interlayer between the tailings and topsoil with two geotextile layers set above and below the interlayer (SLS); the third had a lime interlayer, also with two geotextile layers (SL); and the fourth had a clay interlayer with two geotextile layers (SC). The topsoils were evaluated in a 210-day laboratory column leaching experiments and in a 3-year field cover application at an abandoned Pb-Zn tailings pond (northeastern China). The contents of Pb, Zn and Cd in the soils, leachates, interlayers and leaves of Amorpha fruticosa L. were analysed by inductively coupled plasma optical emission spectroscopy (ICP-OES).Results showed that the pH values of the leachates from the columns increased with time, from 6.5 to the range of 7.5 to 8.03, and the maximum in pH in C1 (tailings), C2 (CT), C3 (SLS), C4 (SL) and C5 (SC) appeared after the 180th day, at 7.85, 7.89, 7.78, 8.03, and 7.89, respectively. The topsoil effectively reduced the concentrations of Pb, Zn and Cd in the leachate, and the addition of a limestone or lime interlayer enhanced the efficiency, especially for Zn and Cd. The Pb, Zn and Cd concentrations in the topsoil that directly cover the tailings were appreciably less than the initial concentrations, resulting from the eluviation. The presence of a limestone or lime interlayer reduced the mobility of Zn and Cd, and a clay interlayer was effective in preventing the migration of Pb and Zn but had less impact on Cd.During the 3-year field experiment, the pH values of the topsoil increased slightly with time, from 7.15 to the range of 7.67 to 8.20. At the end of the experiment, Pb, Zn and Cd concentrations in the topsoil at the SLS, SL and SC plots showed little change compared with the initial value in 2012. Acid-soluble Pb, Zn and Cd concentrations of the upper soil (0–0.1 m) at CT increased from 0.19, 1.95 and 0.11 mg kg− 1 in 2012 to 1.82, 32.87 and 0.56 mg kg− 1 in 2015, indicating that acid-soluble heavy metals migrated from tailings to topsoil. Acid-soluble Cd in topsoil and in the interlayer showed a small increase at plot SC, indicating that Cd may migrate through the clay layer to topsoil with pore water. The Pb contents in leaves at SLS and SL were 2.38 and 3.04 mg kg− 1, which were appreciably lower than at CT and SC, and the Zn and Cd contents in leaves at CT were 45.78 and 0.26 mg kg− 1, which were higher than at SLS, SL and SC. Topsoiling with an interlayer could be a reliable technique for preventing toxic elements from moving downward or upward during ecological restoration of tailings ponds.

National Category
Geochemistry
Research subject
Tillämpad geokemi
Identifiers
urn:nbn:se:ltu:diva-5257 (URN)10.1016/j.gexplo.2016.03.010 (DOI)000375515000013 ()2-s2.0-84961250286 (Scopus ID)351207f3-bc87-4115-b18e-1c8675a7e768 (Local ID)351207f3-bc87-4115-b18e-1c8675a7e768 (Archive number)351207f3-bc87-4115-b18e-1c8675a7e768 (OAI)
Note
Validerad; 2016; Nivå 2; 20160314 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7291-8585

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