Arsenic bioaccessibility in environmentally important arsenic minerals.

The potential risk to humans from incidental ingestion of As-contaminated soil and mine waste is influenced by the mineralogical composition of the As phases present. Using the Solubility Bioaccessibility Research Consortium in vitro assay, simulating gastric conditions, we determined the oral bioaccessibility of As in 16 environmentally important As mineral(oid)s commonly found in mine waste and contaminated soils. Our results revealed a wide range of bioaccessibility values closely related to the solubility of the mineral(oid)s.

Sensitivity of microbial bioindicators in assessing metal immobilization success in smelter-impacted soils.

While plant toxicity reduction remains the primary metric for judging the success of metal immobilization in soil, the suitability of microorganisms as universal indicators of its effectiveness in various contaminated soils remains a point of contention. This study assessed the sensitivity of microbial bioindicators in monitoring metal immobilization success in smelter-impacted soils. It compared plants and microorganisms as indicators of the efficiency of natural Fe-Mn nodules from the Gulf of Finland in immobilizing metals in soils contaminated by a Ni/Cu smelter, on the Kola Peninsula, Murmansk region, Russia.

Tracing anthropogenic mercury in soils from Fe-Hg mining/smelting area: Isotopic and speciation insights.

Mercury (Hg) stable isotope ratios supplemented by Hg solid speciation data were determined in soils in a former Fe-Hg mining/smelting area (Jedová hora, Czech Republic, Central Europe). The dominant Hg phase in the studied soils was found to be cinnabar (HgS). A secondary form of soil Hg(II) was represented by Hg weakly and strongly bound to mineral (micro)particles, as revealed by thermo-desorption analysis.

Bioaccessible metals in dust materials from non-sulfide Zn deposit and related hydrometallurgical operation.

Mining and processing of ores in arid (desert) areas generates high amounts of dust, which might be enriched in potentially harmful elements. We studied dust fractions of ores, soils, and technological materials from mining and related hydrometallurgical operation at former Skorpion Zinc non-sulfide Zn deposit in southern Namibia (closed and placed under maintenance in 2020). Chemical and mineralogical investigation was combined with oral bioaccessibility testing of fine dust fractions (<48 μm and <10 μm) in simulated gastric fluid (SGF) to assess potential risk of intake of metallic contaminants (Cd, Cu, Pb, Zn) for staff operating in the area.

Contaminant release from massive copper metallurgical slags: Insights from long-term monolithic leaching tests.

Compared to compliance leaching tests performed on granular materials, leaching experiments on monolithic slags are more suitable for predicting the contaminant release when large boulders or poured slag layers are submerged in water, a specific environmental scenario typical for many smelting sites. We conducted EN 15863 dynamic monolithic leaching tests on massive copper slags over a prolonged period of 168 d. The patterns of the major contaminant (Cu, Co) fluxes indicated an initial diffusion process followed by the dissolution of primary sulfides with the maximum cumulative releases attaining 75.

Smelter-derived soil contamination in Luanshya, Zambia.

Extensive mining and smelting contributed to the declining quality of Luanshya soils. The local smelter was the epicenter of contamination as shown by a spatial distribution analysis. Closeby soil profiles smelter exhibit extremely high Cu concentrations (up to 46,000 mg kg Cu) relative to deeper layers where only background levels of trace elements were observed.

Contaminant Binding and Bioaccessibility in the Dust From the Ni-Cu Mining/Smelting District of Selebi-Phikwe (Botswana).

We studied the dust fractions of the smelting slag, mine tailings, and soil from the former Ni-Cu mining and processing district in Selebi-Phikwe (eastern Botswana). Multi-method chemical and mineralogical investigations were combined with oral bioaccessibility testing of the fine dust fractions (<48  and <10 μm) in a simulated gastric fluid to assess the potential risk of the intake of metal(loid)s contaminants. The total concentrations of the major contaminants varied significantly (Cu: 301-9,600 mg/kg, Ni: 850-7,000 mg/kg, Co: 48-791 mg/kg) but were generally higher in the finer dust fractions.

Effect of peat organic matter on sulfide weathering and thallium reactivity: Implications for organic environments.

Weathering of Tl-containing sulfides in a model (12-week) peat pot trial was studied to better understand their geochemical stability, dissolution kinetics, alteration products and the associated release and mobility of anthropogenic Tl in organic environments. We also present the effect of industrial acid rainwater on sulfide degradation and Tl migration in naturally acidic peat. Sphalerite (ZnS) was much less stable in peat than other Tl-containing sulfides (galena and pyrite), and thus acted as a major phase responsible for Tl mobilization.

Evaluation of thallium isotopic fractionation during the metallurgical processing of sulfides: An update.

In this study, we report combined Tl isotopic and Tl mineralogical and speciation data from a set of Tl-rich sulfide concentrates and technological wastes from hydrometallurgical Zn extraction. We also present the first evaluation of Tl isotopic ratios over a cycle of sulfide processing, from the ore flotation to pyro- and hydrometallurgical stages. The results demonstrate that the prevailing Tl form in all samples is Tl(I), without any preferential incorporation into sulfides or Tl-containing secondary phases, indicating an absence of Tl redox reactions.

Thallium and lead variations in a contaminated peatland: A combined isotopic study from a mining/smelting area.

Vertical profiles of Tl, Pb and Zn concentrations and Tl and Pb isotopic ratios in a contaminated peatland/fen (Wolbrom, Poland) were studied to address questions regarding (i) potential long-term immobility of Tl in a peat profile, and (ii) a possible link in Tl isotopic signatures between a Tl source and a peat sample. Both prerequisites are required for using peatlands as archives of atmospheric Tl deposition and Tl isotopic ratios as a source proxy. We demonstrate that Tl is an immobile element in peat with a conservative pattern synonymous to that of Pb, and in contrast to Zn.

Metal(loid)s remobilization and mineralogical transformations in smelter-polluted savanna soils under simulated wildfire conditions.

The surroundings of mines and smelters may be exposed to wildfires, especially in semi-arid areas. The temperature-dependent releases of metal(loid)s (As, Cd, Cu, Pb, Zn) from biomass-rich savanna soils collected near a Cu smelter in Namibia have been studied under simulated wildfire conditions. Laboratory single-step combustion experiments (250-850 °C) and experiments with a continuous temperature increase (25-750 °C) were coupled with mineralogical investigations of the soils, ashes, and aerosols.

Slag dusts from Kabwe (Zambia): Contaminant mineralogy and oral bioaccessibility.

The former Pb-Zn mining town of Kabwe in central Zambia is ranked amongst the worst polluted areas both in Africa and in the world. The fine dust particles from the ISF and Waelz slags deposited in Kabwe represent a health risk for the local population. Here, we combined a detailed multi-method mineralogical investigation with oral bioaccessibility testing in simulated gastric fluid (SGF; 0.

Automated mineralogy for quantification and partitioning of metal(loid)s in particulates from mining/smelting-polluted soils.

Topsoils near active and abandoned mining and smelting sites are highly polluted by metal(loid) contaminants, which are often bound to particulates emitted from ore processing facilities and/or windblown from waste disposal sites. To quantitatively determine the contaminant partitioning in the soil particulates, we tested an automated mineralogy approach on the heavy mineral fraction extracted from the mining- and smelting-polluted topsoils exhibiting up to 1920 mg/kg As, 5840 mg/kg Cu, 4880 mg/kg Pb and 3310 mg/kg Zn. A new generation of automated scanning electron microscopy (autoSEM) was combined and optimized with conventional mineralogical techniques (XRD, SEM/EDS, EPMA).

The potential wildfire effects on mercury remobilization from topsoils and biomass in a smelter-polluted semi-arid area.

Wildfires can be responsible for significant mercury (Hg) emissions especially in contaminated areas. Here, we investigated the Hg distribution in topsoils and vegetation samples and temperature-dependent Hg mobilization from biomass-rich topsoils collected near a copper (Cu) smelter in Tsumeb (semi-arid Namibia), where Hg-rich Cu concentrates are processed. The thermo-desorption (TD) experiments conducted on representative biomass-rich topsoils (3.

Thallium stable isotope fractionation in white mustard: Implications for metal transfers and incorporation in plants.

We studied thallium (Tl) isotope fractionation in white mustard grown hydroponically at different Tl doses. Thallium isotope signatures in plants indicated preferential incorporation of the light Tl isotope during Tl uptake from the nutrient solution. Negative isotope fractionation was even more pronounced in dependence on how much the available Tl pool decreased.

Oral bioaccessibility of metal(loid)s in dust materials from mining areas of northern Namibia.

Ore mining and processing in semi-arid areas is responsible for the generation of metal(loid)-containing dust, which is easily transported by wind to the surrounding environment. To assess the human exposure to dust-derived metal(loid)s (As, Cd, Cu, Pb, Sb, Zn), as well as the potential risks related to incidental dust ingestion, we studied mine tailing dust (n = 8), slag dust (n = 5) and smelter dust (n = 4) from old mining and smelting sites in northern Namibia (Kombat, Berg Aukas, Tsumeb). In vitro bioaccessibility testing using extraction in simulated gastric fluid (SGF) was combined with determination of grain-size distributions, chemical and mineralogical characterizations and leaching tests conducted on original dust samples and separated PM fractions.

The impact of wetland on neutral mine drainage from mining wastes at Luanshya in the Zambian Copperbelt in the framework of climate change.

The impact of a natural wetland ("dambo" in Zambia) on neutral mine drainage at Luanshya in the Zambian Copperbelt has been investigated during an intermediate discharge period (July) using a multi-method characterization of solid phase samples, sequential extraction analysis, X-ray diffraction, Mössbauer spectroscopy, and scanning electron microscopy combined with water analyses, isotopic analyses, and geochemical modeling. In the wetland, the principal identified solid phases in sediments were carbonates, gypsum, and ferric oxyhydroxides. A significant portion of the ochres was present as insoluble hematite.

Stability of mercury concentration measurements in archived soil and peat samples.

Archived soil samples can provide important information on the history of environmental contamination and by comparison with recently collected samples, temporal trends can be inferred. Little previous work has addressed whether mercury (Hg) concentrations in soil samples are stable with long-term storage under standard laboratory conditions. In this study, we have re-analyzed using cold vapor atomic absorption spectroscopy a set of archived soil samples that ranged from relatively pristine mountainous sites to a polluted site near a non-ferrous metal smelter with a wide range of Hg concentrations (6.

Thallium contamination of desert soil in Namibia: Chemical, mineralogical and isotopic insights.

We studied arid desert soils from Namibia (Rosh Pinah) that were contaminated with up to 7 mg kg of thallium (Tl) via dust emitted from a local flotation tailing dam. Chemical extractions of waste and soil materials indicated that most of the Tl is strongly bound, in accordance with X-ray diffraction and X-ray absorption spectroscopy data that point to the predominant association of Tl with metal sulfides and phyllosilicates. The isotope fractionation factor εTl of the soil samples (from -0.

Transformation of arsenic-rich copper smelter flue dust in contrasting soils: A 2-year field experiment.

Dust emissions from copper smelters processing arsenic-bearing ores represent a risk to soil environments due to the high levels of As and other inorganic contaminants. Using an in situ experiment in four different forest and grassland soils (pH 3.2-8.

AMOchar: Amorphous manganese oxide coating of biochar improves its efficiency at removing metal(loid)s from aqueous solutions.

A novel sorbent made from biochar modified with an amorphous Mn oxide (AMOchar) was compared with pure biochar, pure AMO, AMO+biochar mixtures and biochar+birnessite composite for the removal of various metal(loid)s from aqueous solutions using adsorption and solid-state analyses. In comparison with the pristine biochar, both Mn oxide-biochar composites were able to remove significantly greater quantities of various metal(loid)s from the aqueous solutions, especially at a ratio 2:1 (AMO:biochar). The AMOchar proved most efficient, removing almost 99, 91 and 51% of Pb, As and Cd, respectively.

Characterization and pH-dependent environmental stability of arsenic trioxide-containing copper smelter flue dust.

Increasing amounts of impurities (especially As) in Cu ores have aggravated the problem of flue dust generation in recent years. As an example from a smelter processing As-rich Cu ores, we characterized a flue dust particularly rich in As (>50 wt%) to understand its mineralogy and pH-dependent leaching behavior, with special emphasis on binding, release and solubility controls of inorganic contaminants (As, Bi, Cd, Cu, Pb, Sb, Zn). Whereas arsenolite (AsO) was the major host for As and Sb, other contaminants were bound in sulfides, arsenates, alloys and slag-like particles.