We used pine tree rings and soil geochemistry to expose the activity of a Pb-Zn smelter in Kabwe, Zambia. We found that local soils are extremely contaminated (up to 16000 mg/kg Pb; 14000 mg/kg Zn; 600 mg/kg Cu in the topsoil). Also, metal bearing particles share their Pb isotopic signature with smelting by-products, and more concerning, metals in tree biomass. We concluded that these metals enter the tree though the bark and leaves, not the roots, implying airborne contamination. Using Pb and C isotopes we mapped the dendrochronology of the tree and verified its susceptibility to changes in smelter production throughout the late 20th century.

Baieta R., Mihaljevič M., Ettler V., Vaněk A., Penížek V., Trubač J., Kříbek B., Ježek J., Svoboda M., Sracek O., Nyambe I. (2021): Depicting the historical pollution in a Pb–Zn mining/smelting site in Kabwe (Zambia) using tree rings. Journal of African Earth Sciences 181, 104246. (DOI)

Arsenic-rich stalactites (0.13-294 g/kg As)  collected from abandoned adits of the Plavno and Mikulov mines (NW Czech Republic) consist of HFA, HFO, kaňkite, schwertmannite, and hydrous manganese oxide mineral phases. These phases were often combined in one stalactite, forming domains, layers and coprecipitates. The microbial communities indicated autotrophic oxidation of Fe(II), As(III), and reduced sulphur compounds as the most notable biological processes influencing the mineralogy in studied stalactites.

Jelenová H., Drahota P., Falteisek P., Culka A. (2021): Arsenic-rich stalactites from abandoned mines: Mineralogy and biogeochemistry. Applied Geochemistry 129, 104960. (DOI)

We combined selective chemical extractions and S isotopes to examine the mobility of As and trace metals (Co, Cu, Ni) in two Czech wetland soils enriched in authigenic Fe-As sulfide minerals through the drying process. We found that As and trace metals released via oxidation of the sulfide phases (particularly Fe sulfides) were almost entirely sequestered by Fe(III) (oxyhydr)oxides, but concomitant acidification resulted in the pH-dependent release of the As(III) and trace metals. Although our results documented the relatively low As mobilization potential under relatively short droughts (several weeks), the preservation of the anoxic conditions must be regarded as a fundamental management strategy of these and other sulfidic wetlands enriched in As.

Drahota P., Peřestá M., Trubač J., Mihaljevič M., Vaněk A. (2021): Arsenic fractionation and mobility in sulfidic wetland soils during experimental drying. Chemosphere 277, 130306. (DOI)

Vanadium is a key critical metal with many applications in the steel and chemical industry. Slags issued from the metallurgical processing of Pb-Zn vanadate ores at Berg Aukas (Namibia) and Kabwe (Zambia) exhibit interestingly high concentrations of V (up to 6140 ppm) and can be considered potential sources of this metal. Two papers published recently by our research group focused on geochemistry and mineralogy of these slags combined with laboratory simulation of the hydrometallurgical extractive processes in view of potential V recovery. The results indicate that, despite high V bulk concentrations and extractabilities, its recovery seems to be non-economical, mainly due to low prices of V (and other associated valuable elements such as Zn) on the global market.

Ettler V., Mihaljevič M., Jarošíková A., Culka A., Kříbek B., Majer V., Vaněk A., Penížek V., Sracek O., Mapani B., Kamona F. (2020): Vanadium-rich slags from the historical processing of Zn-Pb-V ores at Berg Aukas (Namibia): Mineralogy and environmental stability. Applied Geochemistry 114, 104473. (DOI)

Ettler V., Jarošíková A., Mihaljevič M., Kříbek B., Nyambe I., Kamona F., Mapani B. (2020): Vanadium in slags from smelting of African Pb-Zn vanadate ores: Mineralogy, extractability and potential recovery. Journal of Geochemical Exploration 218, 106631. (DOI)

Automated mineralogy has been used to quantitatively determine the contaminant partitioning in the soil particulates originating from heavily polluted mining/smelting sites. This method provides faster data acquisition, the full integration of the quantitative EDS data and better detection limits for the elements of interest. AutoSEM was found to be a useful tool for the determination of the modal phase distribution and element partitioning in the metal(loid)-bearing (As, Cu, Pb, Zn) soil particulates and will definitely find more applications in environmental soil sciences in the future.

Tuhý M., Hrstka T., Ettler V., Automated mineralogy for quantification and partitioning of metal(loid)s in particulates from mining/smelting-polluted soils. Environmental Pollution 266: 115118. (DOI) (open-access)

Mercury distribution in topsoils and vegetation samples and temperature-dependent Hg mobilization simulating wildfires have been investigated near a Cu smelter in semi-arid Namibia. The thermo-desorption experiments performed on the representative Hg-rich topsoils indicated that >91% of the Hg was released at ~340°C, which corresponds to the predominant grassland-fire conditions. Despite the installation of a sulfuric acid plant in the smelter in 2015 and a calculated drop in the estimated Hg emissions (from 1301 ± 457 kg/y for the period 2004-2015 to 67 ± 5 kg/y after 2015), the Hg legacy pool in the smelter surroundings will contribute to wildfire-driven Hg emissions until its complete burn-out. Using the Hg spatial distribution data in the area (184 km²), the estimates indicate that up to 303 kg and 1.3 kg can be remobilized from the topsoils and vegetation, respectively.

Tuhý M., Rohovec J., Matoušková Š., Mihaljevič M., Kříbek B., Vaněk A., Mapani B., Göttlicher J., Steininger R., Majzan J., Ettler V. (2020): The potential wildfire effects on mercury remobilization from topsoils and biomass in a smelter-polluted semi-arid area. Chemosphere 247, 125972. (DOI)

This study investigated As-enriched wetland at the Smolotely-Líšnice Au district (Centra Bohemia) using the combination of geochemical (soil and pore water analyses, S isotopes), mineralogical (microprobe, Raman spectrometry) and biological (DNA extraction) method. In this paper, Magda and her co-authors identified a complex assemblage of As and Fe sulfides (realgar, bonazziite, pyrite, greigite) on the fragments of natural organic matter, which play an active role (very fast microbial sulfate reduction vs. slow transfer of solutes) in arsenic immobilization in polluted wetland systems.

Knappová M., Drahota P., Falteisek L., Culka A., Penížek V., Trubač J., Mihaljevič M., Matoušek T. (2019): Microbial sulfidogenesis of arsenic in naturally contaminated wetland soil. Geochimica et Cosmochimica Acta 267, 33-50. https://doi.org/10.1016/j.gca.2019.09.021

We combined elemental and isotopic studies, leaching techniques and speciation modeling to describe Cu and Pb behavior in contaminated soil profiles of Kombat, Namibia. Tailings, soils and bedrock samples were analyzed. We described pollutants’ behavior in detail for different type of soils and concluded that migration is highly dependent on soil characteristics and element speciation shown by variations, or lack thereof, in concentrations, δ⁶⁵Cu and ²⁰⁶Pb/²⁰⁷Pb values with depth.

Mihaljevič M., Baieta R., Ettler V., Vaněk A., Kříbek B., Penížek V., Drahota P., Trubač J., Sracek O., Chrastný V., Mapani B. S. (2019): Tracing the metal dynamics in semi-arid soils near mine tailings using stable Cu and Pb isotopes. Chemical Geology 515, 61-76. (DOI)

We used a multi-method approach for characterization of dust from mines and smelters in the northern Namibia. In vitro bioaccessibility testing in simulated gastric fluid (SGF) indicated that As, Pb (and also Cd to a lesser extent) exceeded tolerable daily intake limits for these contaminants in the case of slags and smelter dusts, but the exposure risk for local population is only important at the unfenced disposal sites.

The paper published in Environment International is open-access. Ettler V., Cihlová M., Jarošíková A., Mihaljevič M., Drahota P., Kříbek B., Vaněk A., Penížek V., Sracek O., Klementová M., Engel Z., Kamona F., Mapani B. (2019): Oral bioaccessibility of metal(loid)s in dust materials from mining areas of Namibia. Environment International 124, 205-215. (DOI)

A complete set of new thermodynamic data has been determined for three Al and Fe arsenate minerals: mansfieldite, angelellite and kamarizaite.

Majzlan J., Nielsen U.G., Dachs E., Benisek A., Drahota P., Kolitsch U., Herrmann J., Bolanz R., Števko M. (2018): Thermodynamic properties of mansfieldite (AlAsO₄·2H₂O), angelellite (Fe₂(AsO₄)₂O₃) and kamarizaite (Fe₃(AsO₄)₂(OH)₃·3H₂O). Mineralogical Magazine 82, 1333-1354. (DOI)