Historic Copper Research Articles

Biogeochemical impact of historical submarine mine tailings on benthic ecosystems in the Repparfjord (Northern Norway)

Historical copper mine tailings deposited in the Repparfjord, Northern Norway, provided new insight into the biogeochemical impact of submarine tailings disposals on high-latitude coastal ecosystems. The submarine tailings disposal in the Repparfjord represents a product of mining activities between 1972 and 1979. Their environmental impact has been extensively studied during the last decade, but geochemistry of the sediment pore water, which is crucial to assess and monitor the in-situ metal leaching and bioavailability, has never been analysed. The actual impact on the benthic fauna remains poorly known. Therefore, this study couples the pore water chemistry and the foraminiferal analysis obtained from selected sediment cores (gravity core, multicore, box cores) to examine metal stability and the past and current status of the foraminifera community. We measured down-core sulfate and trace metal concentrations and Eh-Ph and applied the Shannon index, the AZTI's Marine Biotic Index (F-AMBI) index and the foraminiferal abnormality index. This study confirms the ongoing leaching of Cu from the underlying mine tailings and release across the sediment-water interface. Leaching of Ni, Zn and Pb have been attributed to weathering of natural bedrock lithologies. The original benthic foraminiferal community disappeared almost entirely during the disposal period, and now it is dominated by stress-tolerant and opportunistic species like Bulimina marginata and Spiroplectammina biformis. Anyhow, against previous assumptions, the community composition changed, while the overall diversity and abnormalities (FAI) shell formation is unaffected by elevated Cu concentrations.

Contamination of urban soils in a historical mining town of northern Chile

In northern Chile, economic activities related to mining and thermoelectric energy have existed in the city of Tocopilla since the early 1900s and metal concentrations in soils have likely been altered by historic anthropogenic activities. To assess the concentrations of Cu, Zn, Pb, Ni, Co, and Cr in urban soils of Tocopilla, a total of 70 superficial (2 cm) and 70 deep (20 cm) soil samples were collected in 2014. Furthermore, to analyze concentration changes in soils over time, 18 superficial (5 cm) samples were collected in 2020–2021. A numerical evaluation (geoaccumulation index, and enrichment factor), principal component analysis, and spatial distribution approach were applied to infer geogenic and anthropogenic influence on the concentrations of these elements. The main conclusions of this research indicate that urban soils of Tocopilla contain geogenic Cu, Zn, Pb, Ni, Co and Cr. However, elevated concentrations of Cu, Zn, and Pb cannot be attributed to a geogenic origin alone, as a proportion of their enrichment is considered to be anthropogenically sourced. The contamination of anthropogenic elements has been found to be related to historic copper mining and thermoelectric energy production. Furthermore, when compared to other sites globally, median concentrations of Cu (945 mg/kg in 2014 and 823 mg/kg in 2020) and Zn (305 mg/kg in 2014 and 196 mg/kg in 2020) in superficial urban soils are among the highest worldwide. Regarding 2020–2021 sampling, Zn and Pb concentrations have increased, while Cu, Cr, Co, and Ni have remained similar to the 2014 samples.

Sediment quality classification in freshwater lakes predicted by the history of treatment with copper-based aquatic algaecides.

Copper-based aquatic algaecides have been widely used in the management of aquatic macrophyte and harmful algal blooms for decades due to their effectiveness and low cost. However, repeated treatment of freshwater lakes results in the accumulation of copper in the sediment, which may adversely affect the ecosystem of the lakes through toxicity to benthic invertebrates and other organisms. Consequently, copper-based aquatic herbicides and algaecides have been frequently subjected to regulations aimed at preventing further ecological deterioration in treated waterbodies. Many states in the US are taking or considering taking an approach that limits or prohibits copper treatment in waterbodies. Freshwater lakes with extensive historical copper treatments typically have significantly higher concentrations of copper in the sediment than untreated lakes. However, the correlation between the extent of the treatments and level of copper accumulation in the sediment has not been quantitatively characterized. In the present study, between 2006 and 2017, copper concentrations were measured in the sediment from selected lakes in New York State with different histories of copper-based aquatic algaecide treatment. Analysis of these data confirmed findings from earlier studies conducted by New York State that lakes with histories of copper treatment have significantly higher copper concentrations in the sediment. It also demonstrated that sediment copper concentrations were significantly higher in the sublittoral zone than the littoral zone in treated lakes. Moreover, a positive correlation was detected between sediment copper concentrations and the total number of treatments with copper-based aquatic algaecide for both littoral and sublittoral zones (p-value = 7.94 × 10-8 and 3.1 × 10-13, respectively). This relationship can be used as a screening tool for regulatory agencies to identify lakes with sediment copper levels possibly higher than the toxicity threshold for aquatic life. Consequently, additional ecological risk assessment may be required before allowing future treatment with copper-based aquatic algaecides. Integr Environ Assess Manag 2024;20:1586-1597. © 2024 SETAC.

Sustain China's copper resources with domestic mining, trading, and recycling

Rapid urbanization and industrialization made China the world's largest refined copper producer and consumer. Insufficient copper ore reserves necessitated significant imports and scrap copper recycling. Using material flow and scenario analysis, this study examined historical copper supply and assessed future supply-demand balance. The results show that China's refined copper consumption soared from 2.3 Kt in 1949 to 14.43 Mt in 2020, with imports rising from 1.5 Kt to 11.77 Mt, resulting in a 75 % external dependence. In addition, primary copper importers were concentrated in the Americas. In 2020, China accumulated around 120 Mt of in-use stocks, enabling urban mineral resource development. Forecasted results indicate a persistent copper supply deficit. Recycling copper scrap is crucial to bridge the supply-demand gap. This study enhances understanding of copper's historical supply and consumption, providing policymakers with suggestions for sustainable copper resource management.

The Effect of Exposure Condition on the Composition of the Corrosion Layers of the San Carlone of Arona

The Colossus of San Carlo Borromeo, named San Carlone for its large dimensions, represents a unique opportunity to study the long-term effects of atmospheric corrosion on patina formation on historic copper sheets. The sculpture’s large dimensions, complex geometry, direct visitor interaction, and exposure conditions generate different microclimates. The purpose of this study is to understand how and to what extent these microclimates affect the formation of the copper patinas. The results show that microclimates play a key role in patina formation: in external surfaces exposed to rain, the main constituent is brochantite, whereas a wider variety of corrosion products have been found in sheltered and internal surfaces, such as antlerite, atacamite, copper oxalate, posnjakite, and anglesite.

Investigating Manganese-oxidizing microbial Biofilms in a historic Copper Mine of Upper Frankonia

Providing evidence for presumed chemolithoautotrophic manganese oxidation remains a major and challenging objective in subsurface microbiology. Here, we report on the dissection of blackish, leathery microbial biofilms discovered in the “Goldene Falk”, a historic copper mine in Northern Bavaria, with mine shafts originating back to the 15th centrury. Biogeochemical analysis of the biofilm indicated a notable enrichment of manganese oxides (MnOX), with Mn making up for more than 10% (dry weight) of the deposits. STXM analysis suggested a clear biogenic origin of MnOX in situ. Characteristic nodules of MnOX with microbial cells attached were also found in aerobic Mn-oxidizing enrichment cultures set up in minimal media in the lab. The biofilms obtained from the mine were also subjected to amplicon and metagenomic sequencing,revealing a vast diversity of presumably chemolithoautotrophic and heterotrophic microbial lineages, including members of the Pyrinomonadaceae, Rhizobiales, Methylomirabilaceae and also lineages within the Nitrospiraceae previously reported to be associated with lithotrophic Mn oxidation. We reconstructed >100 high-quality bacterial genomes (MAGs), many of them carrying genomic signatures of biogenic Mn oxidation (albeit non-lithotrophic). We continue to investigate the biofilms, our enrichment cultures and the metagenomic data obtained from the mine for further evidence of possible autotrophic manganese oxidation, the macroscopic leathery biofilm representing a likely habitat for these still enigmatic microbes. Indications for nitrogen and sulfur cycling also ongoing in the biofilms will also be discussed. This research contributes to a better understanding of the yet-enigmatic capacities of the microbiota in man-made subsurface environments.

Mineralogical Characterization of Historic Copper Slag to Guide the Recovery of Valuable Metals: A Namibian Case Study.

The depletion of the ore reserves in the world necessitates the search for secondary sources such as waste products (tailings and slag). The treatment and cleaning up of such secondary sources also has a positive impact on the environment. A smelter in Namibia we examined had historic slag which accumulated over decades of its operating life, thus posing the challenge of how best to collect representative samples to evaluate and propose viable methods of recovering contained metals. In this study, analytical and mineralogical characterization of the slag was performed using X-ray fluorescence (XRF) analysis, atomic absorption spectrometer (AAS), ICP-OES, scanning electron microscopy energy dispersive spectroscopy (SEM-EDS) analysis, and optical microscopy analysis. The chemical analyses showed that the metal values contained in the slag were mainly copper, lead, and zinc whose average contents were approximately 0.35% Cu, 3% Pb, and 5.5% Zn. About 10.5% Fe was also contained in the slag. Germanium was detected by scanning electron microscopy, but was however below detection limits of the chemical analysis equipment used. Based on the results, approximate conditions under which the different slag phases were formed were estimated and the recovery routes for the various metals were proposed. Analysis by both optical and scanning electron microscopy revealed that Zn and Fe occurred mainly in association with O as oxides, while Cu and Pb were mainly associated with S as sulphides. The slag consisted of three different phases, namely the silicate phase (slag), metallic phase and the sulphide phases. The phases in the slag were mainly silicate phases as well as metallic and sulphide phases. It was observed that the metallic and sulphide phases were dominant in the finer size fractions (-75 µm) whereas the sulphide phase was also present in the coarser size fractions (+300 µm). An important finding from the microscopy examination was that the sulphide phases were interstitial and could be liberated from the slag. This finding meant that liberation and subsequent concentration of the sulphide phases was feasible using conventional processing techniques.

Novel Microemulsions with Essential Oils for Environmentally Friendly Cleaning of Copper Cultural Heritage Artifacts.

Cleaning represents an important and challenging operation in the conservation of cultural heritage, and at present, a key issue consists in the development of more sustainable, "green" materials and methods to perform it. In the present work, a novel xylene-in-water microemulsion based on nonionic surfactants with low toxicity was obtained, designed as low-impact cleaning agent for metallic historic objects. Phase diagram of the mixtures containing polyoxyethylene-polyoxypropilene triblock copolymer Pluronic P84 and D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) as surfactants, water, ethanol and xylene was studied, and a microemulsion with low surfactant content was selected as suitable cleaning nanosystem. Essential oils (EOs) from thyme and cinnamon leaf were added to the selected microemulsion in order to include other beneficial properties such as anticorrosive and antifungal protection. The microemulsions with or without EOs were characterized by size, size distribution and zeta potential. The cleaning efficacy of the tested microemulsions was assessed based on their ability to remove two types of artificial dirt by using X-ray energy dispersion spectrometry (EDX), scanning electron microscopy (SEM), contact angle measurements and color analysis. Microemulsions exhibit high capacity to remove artificial dirt from model copper coupons in spite of very low content of the organic solvent. Both thyme and cinnamon oil loading microemulsions prove to significantly reduce the corrosion rate of treated metallic plates compared to those of bare copper. The antifungal activity of the novel type of microemulsion was evaluated against Aspergillus niger, reported as main treat in biocorrosion of historic copper artifacts. Application of microemulsion with small amounts of EOs on Cu plates inhibits the growth of fungi, providing a good fungicidal effect.

Laser diagnostics and processing of historical and artificial copper patina

Natural and artificial patination is crucial for the protective qualities and appearance of artefacts and roofings. Patina on historical copper roofing sheets from the Belvedere Palace built by Prince Eugene of Savoy in Vienna 1723 were compared with artificial cuprite and brochantite coated copper sheets employing scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) imaging together with profilometry based on EDX and laser-induced breakdown spectroscopy (LIBS) with 4 ns laser pulses at 266 nm. Non-destructive cleaning with this UV wavelength was discussed. A sufficient fluence cleaning window, the difference between the destruction and the cleaning threshold fluence, of more than one order of magnitude could be realized. The quantification of contamination states on the natural patina samples by colorimetry testing represented a useful tool for future quantification tests of laser cleaning and colour changes.

Dendroremediation Potential of Six Quercus Species to Polluted Soil in Historic Copper Mining Sites

Green remediation of severely contaminated soils around mining sites can be achieved using suitable woody plants such as Quercus species, but their phytoremediation potential has not been well evaluated yet. Six Quercus species, which were popular in ecological restoration and landscape application in east China, were selected and evaluated for their phytoremediation potential of metal polluted soil using a pot experiment that lasted for 150 d. The results suggested that Quercus species exhibited high tolerance to multi-metal contamination of Cu (9839 mg·kg−1), Cd (8.5 mg·kg−1), and Zn (562 mg·kg−1) with a tolerance index (TI) ranging from 0.52 to 1.21. Three Quercus (Q. pagoda, Q. acutissima, and Q. nuttallii) showed relatively higher tolerance with TIs of 1.08, 1.09, and 1.21, respectively. Above-ground tissues accounted for most of the total biomass in T1 (mixture of clean and polluted soil, 50%) and T2 (100% polluted soil) treatments for most species. The Cu contents in plant tissues were in the order of root > leaf > stem, whereas Zn exhibited the order of leaf > stem > root, and Cd showed divergent mobility within the Quercus species. All the Quercus species exhibited higher capacity for Zn phytoextraction with translocation factor (TF) over 1 and Cu/Cd phytostabilization with TFs lower than 1. The analytic hierarchy process-entropy weight model indicated that Q. virginiana and Q. acutissima were two excellent species with evident phytoremediation capacity of Cu, Cd, and Zn co-contaminated soil. Taken together, Quercus species showed great potential for phytoremediation of soils severely polluted by Cu, Cd, and Zn around historic mining sites. Application of Quercus species is a green remediation option with low-maintenance cost and prospective economic benefit for phytomanagement of historic mining sites.

Important Explorations on Surface Corrosion of the Copper Coins Sourced from the Qing Dynasty.

Surface corrosion is considered to be a main reason for the surface pattern damages of copper coin sourced from the Qing Dynasty. In this study, micromorphology and the structural feature of the copper coins were analyzed to determine their corrosion mechanisms. The results revealed that the etching rates successively reduced with decreasing corrosion thickness, possibly because of unique macrofeatures of the surface pattern. Variable phases, bonding morphologies, and three-/two-dimensional structures of Ql-TB (Qianlong-Tongbao) coins were visibly different at the microscale, which induced disproportional stresses and microscopic cracks, facilitating an unhindered entry of oxide and hydroxyl (OH−) ions. These species resulted in the competitive interplay of self-healing and self-degradation mechanisms on the coin surfaces and formed corrosion thickness of ~9.31 μm and a mean corrosion rate of ~2.7%. This study provided an important guideline for preserving microstructures and surface patterns of historical copper coins.

Probabilistic risk assessment of mine-derived copper in the Ok Tedi/Fly River, Papua New Guinea

The Ok Tedi mine discharges waste rock and tailings into the Ok Tedi River in Papua New Guinea. This has resulted in elevated copper concentrations throughout the Ok Tedi/Fly River system, which can potentially impact aquatic biota. Ten years of measured copper and toxicity monitoring data were used to assess the risk of chronic effects from the mine-derived copper. Cumulative probability plots of dissolved and labile copper were compared to a species sensitivity distribution (SSD) of published copper toxicity data for four regions of the river. The Cu-SSD was used to estimate the risk of chronic effects to aquatic organisms in the Ok Tedi/Fly River at a range of potential copper exposure scenarios. The risk to species at the median labile copper concentration for each region showed a gradient effect with distance downstream from the mine and only the most sensitive (0.2–11%) species were at risk. There were copper exceedances of the region-specific guideline values (GV) and default guideline value (DGV) 88% and 74% of the time, respectively, in the Ok Tedi region (closest to the mine) and this is considered a high risk of chronic effects. Measured copper concentrations in the middle Fly River, lower Fly River (farthest downstream of the mine) and the river at Kiunga (reference site) exceeded the region-specific GVs and DGVs less frequently to rarely and present a lower risk of chronic effects from copper. The risk was supported using toxicity tests with the local microalgal species Chlorella sp. Comparison of recent (2010−2020) and historical (1996–2004) copper monitoring data from the Ok Tedi/Fly River indicates a decrease in the labile copper concentrations (30–76%) at key sites from impacted regions and a subsequent decrease in risk. This coincides with improved mining practices aimed at reducing the copper load into the Ok Tedi/Fly River.

Reconstruction of Copper Smelting Technology Based on 18–20th-Century Slag Remains from the Old Copper Basin, Poland

This research was conducted on historical copper slags from Leszczyna and Kondratów in Lower Silesia, Poland. The area, formerly known as the Old Copper Basin, was a mining and smelting centre between the 18th and 20th centuries, with a dominant period in the 19th century. Cu-carbonates and residual chalcocite dominate local strata-bound copper deposits. Ore bodies are restricted to carbonate strata. A geochemical and mineralogical study of slag samples from four research sites allowed us to establish that a low amount of sulphur in slags results from S-poor ores, and pyrite with gypsum was implemented as reducing agents. Arkose sandstones served as a flux. During smelting, oxygen availability was limited, and temperature exceeded 1200 °C (18th- and 19th-century smelting) and 1400 °C (20th-century smelting). Calculated viscosity indexes mark the low efficiency of metal separation between the silicate and metallic phases. The skeletal and dendritic form of the crystals proved that slag melt was relatively rapidly cooled after formation, usually in air conditions. We estimated that approx. 2000 m3 of slag was created during the leading smelter (Stilles Glück) activity. The research provided various details of the historical copper smelting technological process in Leszczyna and Kondratów.

Legacy sources to new exposures. A preliminary lead risk assessment to children in the Falun mining area

BACKGROUND AND AIM: Like many of Sweden’s metropolitan areas, the city of Falun faces a shortage of affordable housing. The city’s proximity to a historic copper mine presents unique challenges for the growing high-density service and industrial area. Concerns about the feasibility and risks associated with building new housing on land contaminated by the legacy of mining and metal industries motivate a new risk assessment using current reference values for lead. The aim of this project is to undertake a preliminary environmental health-based risk assessment on the lead levels surrounding the mining area, based on previous samples (dust, soil, biomarkers). METHODS: We use environmental samples and research done in Falun from 1986 to 1998 to predict blood lead levels (BLL) today by employing the Integrated Exposure Uptake Biokinetic (IEUBK) software. We further compare calculated to measured BLL from 1993 and to current threshold values from Environmental Protection Agency (EPA) and the Scientific Committee on Health and Environmental Risks (SCHER). RESULTS:The average measured BLL for children 4 years is 3.7 µg/dL and 4 years is 2.8 µg/dL. IEUBK BLL estimates are 1.2-1.4 µg/dL and 0.9-1.1 µg/dL, respectively. Both averages are below the 5 µg/dL threshold used by EPA, and higher or equal than the 1.2 µg/dL associated with the 0,5 µg/dL bodyweight/day tolerable daily intake. CONCLUSIONS:Based on measured and calculated BLL, the exposure exceeds currently acceptable safe levels. However, samples were taken before the ban on leaded gasoline in Sweden in 1994, but also around active mining and smelting. Furthermore, the lead from mining operations in Falun has low bioavailability 0.5%-2%. The lead in the respirable fraction is more associated with smelting operations and leaded gasoline, which have not existed for almost 30 years. Together, these factors result in a possible overestimation of the current lead exposure to children in Falun. KEYWORDS: Built environment, Heavy metals, Exposure assessment-biomarkers of exposure, Risk assessment, Children's environmental health

Recovery of Cobalt, Copper and Zinc from Küre-Kastamonu Historical Copper Slag by High Pressure Oxidative Acid Leaching

Recovery of Cobalt, Copper and Zinc from Küre-Kastamonu Historical Copper Slag by High Pressure Oxidative Acid Leaching

Novel Procedure for Brochantite Based Pigment Production and Its Immobilization for Restoration of Historical Copper Objects

The article deals with the preparation of artificial copper pigment based on brochantite. The pigment was prepared by slow additions of sodium hydroxide solution into the solution of copper sulphate. The studied parameters were addition rate, solutions concentrations, ferrous ion addition, and filtration time. The prepared pigments were evaluated by means of X-ray diffraction and spectrophotometry. Subsequent pigment immobilization in an acrylate varnish was also studied. Observed parameters were influenced by solvent type, mechanical or chemical dispersion, and natural aging in an aggressive outdoor atmosphere. Pigment containing varnishes were evaluated by means of spectrophotometry, optical profilometers, and pull-off test. Slow hydroxide addition allows the formation of brochantite pigment. Fast filtration limits backward pigment decomposition. Ferrous ion improves pigment color closer to natural copper patina. The ideal immobilization procedure includes ethylacetate as a solvent and mechanical dispersion. The varnish filled with pigment provides sufficient adhesion to the metallic copper substrate as well as long-term color stability in the outdoor atmosphere.

Prospective (Bio)leaching of Historical Copper Slags as an Alternative to Their Disposal

The aim of this study was to evaluate the feasibility of (bio)hydrometallurgical methods for metal extraction from historical copper slags. Two types of slags (amorphous slag—AS, and crystalline slag—CS) were subjected to 24 to 48 h of leaching with: (i) Sulfuric acid at 0.1, 0.5, and 1 M concentrations at 1%, 5%, and 10% pulp densities (PDs); and (ii) normality equivalent (2 N) acids (sulfuric, hydrochloric, nitric, citric, and oxalic) at pulp densities ranging from 1% to 2%. Bioleaching experiments were performed within 21 days with Acidithiobacillus thiooxidans accompanied by an abiotic control (sterile growth medium). The results demonstrated that the most efficient treatment for amorphous and crystalline slag was bioleaching at 1% PD over 21 days, which led to extraction of Cu at rates of 98.7% and 52.1% for AS and CS, respectively. Among the chemical agents, hydrochloric acid was the most efficient and enabled 30.5% of Cu to be extracted from CS (1% PD, 48 h) and 98.8% of Cu to be extracted from AS (1% PD, 24 h). Slag residues after leaching were characterized by strong alteration features demonstrated by the complete dissolution of fayalite in the case of CS and the transformation of AS to amorphous silica and secondary gypsum. Based on this study, we conclude that amorphous slag is a more suitable candidate for potential metal recovery because of its generally high susceptibility to leaching and due to the generation of residue significantly depleted in metals as the end product. The inventory of economically relevant metals showed that 1 ton of historical copper slag contains metals valued at $47 and $135 for crystalline and amorphous slag, respectively, suggesting that secondary processing of such materials can potentially be both economically and environmentally viable.

A colorimetric chemosensor for quantification of exchangeable Cu2+ in soil

Chemosensors have already demonstrated potential for the detection and imaging of metal ions in solutions and biological systems, however, their applications to soil analysis are limited. This study explores the potential of utilizing a chemosensor for the detection of exchangeable Cu2+ in soils via qualitative (solution visual color change) and quantitative (UV–Vis spectrophotometry) approaches. Montmorillonite and kaolin clays were doped with Cu(NO3)2 solutions from 2.5 to 50 mM, and contaminated soil samples were collected from a historic copper mine. The exchangeable Cu2+ was extracted using a standard CaCl2 cation exchange approach, and the Cu2+ concentration in the resulting solutions determined by UV–Vis spectrophotometry, using a chemosensor, and compared to traditional ICP-MS analysis. Analytical results showed that the chemosensor provided a visual response in contaminated soils at concentrations of 25 μM and quantitative detection to concentrations of 1 μM using UV–Vis spectrophotometry. This work demonstrates the first reported chemosensor for exchangeable Cu2+ with application to soil systems.

Rapid metal mobilisation through litter, water and bioweathering as the legacy of historical copper smelting

Though activities have long ceased, historical mining sites may continue to represent a risk to the environment and human health through long-time leaching processes. This study was undertaken to assess the immediate environmental risk posed by historic metallurgical slags upon contact with litter (Fagus sylvatica leaves, Picea abies needles) and stream water. Further, the contribution of direct slag phase bioweathering was investigated using a soil solution favouring microbial growth (biostimulation) versus aqueous sterile soil extracts. The slags' exposure to Acidithiobacillus thiooxidans mimicked the extremely acidic conditions that will eventually develop under long-term weathering of the sulfidic phases present in the slags (e.g. bornite, chalcopyrite). The risk of metal mobilisation was assessed by means of both bio-chemical leaching experiments (quantification by triple quadrupole inductively coupled plasma mass spectrometry QQQ-ICP-MS) as well as phytotoxicity (Zea mays germination; direct contact and soil pot experiments). Potential metal donor slag phases were identified by scanning electron microscopy (SEM-EDS). It was shown that slags would be categorised as hazardous waste when remaining in contact with the studied weathering solutions. Lead was the most mobile element leaching from slags (up to 86%) and exceeded the legal limits for classification as a non-hazardous waste for all executed treatments. Biostimulation had little effect on Cu leaching (up to 2.6% versus 2.5% for the sterile soil extract, respectively). Litter derived solutions, in contrast, enhanced glass dissolution instead of heavy metal bearing phases. Metal leaching was rapid, raising concerns for peak loads on slag exposure to changing biogeochemical conditions. Extremely acidic conditions and bioleaching by A. thiooxidans were shown to result in metal-enriched leachates (up to 92% of Zn) as well as the lowest germination rate in Zea mays, implying a long term risk by sulphide bioweathering. Five week pot experiments with a soil/slag mixture and Zea mays revealed poor growth in all studied conditions. However, a bacterially derived citric acid was found to improve root and shoot development, possibly due to alleviating the toxic effect of some elements. Due to the observed phytotoxicity, we conclude that the phytoremediation/rehabilitation of slag impacted soils may be limited. The search for a metal tolerant plant species that would be efficient in terms of biomass production and metals uptake is a perspective of this work.

The origin and evolution of copper patina colour

The copper patina colour has been systematically explored through a large set of short- and long-term exposed copper metal samples. The initial brown-black appearance is attributed to semiconducting properties of cuprite (Cu2O) and fully attained at thickness 0.8 ± 0.2 μm. The characteristic green-blue appearance is due to the colour forming Cu(II)-ion in the outer patina layer which needs to be 12 ± 2 μm to fully cover the inner cuprite layer. No significant influence of atmospheric environment on patina colour is discerned. The green-blue patina colour on historic copper was attained after shorter exposures than in modern copper due to more inhomogeneous microstructure.