Martin Mihaljevič

Wildland fires affect the trace element cycles at the vegetation–soil interface.

In?this study, we?present a?detailed geochemical characterisation and stable isotope systematics of?silver?(Ag) in?a?mining waste facility at?the Namib Lead & Zinc mine in?Namibia (Africa). We?examined a?series of?flotation tailings and or...

Untreated neutral metalliferous mine drainage sludge deposited without environmental protection for over a century was studied to assess its long-term stability. The lack of long-term stability data on such untreated sludge represents a critical knowledge gap in mine waste management. We characterized the sludge’s mineralogy, chemistry, and metal(loid) mobility using XRD, SEM–EDS, and a suite of leaching tests (deionized water, 0.01 M CaCl ₂ , and pH-static extractions), supported by geochemical modeling. Key findings show that even after ~ 100 years, the sludge’s phase composition and metal(loid) content remain largely unchanged, with high concentrations of As, Cd, Pb, and Zn comparable to those in the overlying Technosol. These metal(loid)s form their own phases (e.g., cerussite, smithsonite) or are adsorbed onto goethite and clays, limiting their release under the sludge’s natural pH (6.3–7.1). Leaching is primarily confined to the sludge–Technosol interface, where the Technosol’s low pH (~ 4) promotes mobilization of Cd, Pb, and Zn (e.g., up to 342 mg kg ⁻¹ Zn and 278 mg kg ⁻¹ Pb in CaCl ₂ extracts from the Technosol). These findings are consistent with PHREEQC modeling. A remediation scenario involving raising the Technosol pH to ≥ 7 (e.g., by liming), combined with metal(loid)-binding amendments (amorphous Mn oxide, biochar, zeolite), could reduce metal(loid) migration from the sludge to the Technosol by ~ 99.9% (especially for Cd, Pb, and Zn) and significantly decrease their bioavailability to plants. This study provides the first field-based evidence that untreated neutral mine drainage sludge can remain geochemically stable for over a century, and suggests remediation strategies to ensure environmental safety of such historical mine residues.

Waste metallurgical slags have shown the potential to serve as a source of critical raw materials. In this study, we examined the extraction of Cu and Zn from a fine-grained copper slag from the Tsumeb smelter (Namibia). A combination of chemical analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and automated mineralogy (autoSEM) was used to determine its elemental and mineralogical composition. Silicate glass was determined as being the most abundant phase (over 90 area %) and the dominant host phase for the target elements (58–70% of the total Cu, over 90% of the total Zn). Based on these results, the reprocessing of the slag by sulfide flotation and subsequent pyrometallurgical treatment would be inefficient. For the extraction of Cu and Zn, a hydrometallurgical approach using acid leaching was proposed. Extraction tests to simulate agitation leaching were carried out by leaching the original fine-grained material in H₂SO₄ (20, 50, and 100 g/l) at liquid/solid (L/S) ratios of 5, 10, and 20 kg/l and ambient temperature for 1 and 6 h. The extraction efficiencies increased with the increasing acid concentrations, L/S ratios, and leaching time, reaching up to 70% for Cu and 94% for Zn. High extraction efficiencies of As were reached (up to 91%), possibly lowering the environmental hazards posed by the original material. Graphical Abstract

Dermoloma is traditionally known as a small genus of agarics classified in the family Tricholomataceae. This study implemented a multilocus phylogeny of six DNA regions to recognize phylogenetic species within the genus. The species concept is reinforced by observations of well-defined morphological characters enhanced by long term sampling effort in Europe and North America. Thirty European Dermoloma species are described, including 16 new species from Europe and three from North American. These species are classified into two subgenera morphologically distinguished by spores with positive or negative amyloid reaction. A new genus Neodermoloma is introduced for the Dermoloma-like species N. campestre. Localized or continental-scale species endemicity was confirmed based on studied material, but more inclusive phylogenetic clustering supported a mixture of North American species among the European clades. Of the 22 names validly published from Europe prior to this study, 11 could be assigned to well-defined Dermoloma species recognized here. Of the remaining 11 names, two were considered representing Dermoloma species not recorded since their description, and nine were established as later synonyms of other species. Morphological studies of Dermoloma are challenging due to the relatively low number of characters suitable for identification of species. The majority of morphological characters showed continuous variation with high overlap throughout the genus. For this reason, species identification requires an awareness of morphological variability within species, and multiple distinguishing characters need to be combined, and furthermore, often a barcode sequence is needed for a certain identification. Stable isotope analysis in Dermoloma of δ¹³C and δ¹⁵N revealed an ecological signature similar to known CHEGD fungi, i.e. Clavariaceae and Hygrocybe s.l. This indicates that Dermoloma species are biotrophic but neither ectomycorrhizal nor saprotrophic and may form mutualistic root endophytic associations with vascular plants.

The bioaccessible fraction of metal(loid)s in tailings dust decreases along the climatic gradient from semiarid to arid environments as a function of differences in the mineralogical and geochemical compositions.

In historic mining towns, where mining activities were abandoned many decades or even centuries ago, legacy contaminations can be remobilized and redispersed, representing a threat for the environment and human health. This study focuses on urban soils (n = 19) in the town of Jihlava, the Czech Republic, one of the medieval centers of silver mining in central Europe. The basic geochemical characterization of the soils was combined with mineralogical investigations to understand the solid speciation of the metal(loid) contaminants, oral bioaccessibility tests, and exposure assessment. The total concentrations of the metal(loid)s in the original soils were not excessively high (up to 45.8 mg As/kg, 19.2 mg Cd/kg; 205 mg Cr/kg; 91.8 mg Cu/kg, 163 mg Pb/kg, 253 mg V/kg, 262 mg Zn/kg), although, in some cases, they exceeded the regulatory guidelines for agricultural and/or residential soils. A substantial increase in the metal(loid)s contents was confirmed for the < 48-µm soil fraction that was later used for the bioaccessibility tests. Scanning electron microscopy and the electron microprobe showed that ore-derived primary sulfides were rare in the studied soils. Still, hydrous ferric oxides rich in Cu, Pb and Zn and fragments of metallurgical slags composed of metal-containing glass and silicates (olivine) were prone to dissolution during extraction in a simulated gastric fluid (SGF, glycine solution acidified to pH 1.5 by HCl). The maximum bioaccessible concentrations corresponded to 4.69 mg As/kg, 1.75 mg Cd/kg, 2.02 mg Cr/kg, 20.3 mg Cu/kg, 81.6 mg Pb/kg, 16.2 mg V/kg, and 233 mg Zn/kg. Exposure estimates were carried out for children (10 kg) as a target group and a conservative soil ingestion rate (100 mg/d). However, the daily intake of all the studied contaminants was far below the tolerable limits. Our results show that the human health risk based on incidental soil ingestion in the studied area seems limited.

Samples of the bones of 47 individuals from 46 Czech and Moravian ossuaries were dated by the ¹⁴C method and analyzed for the collagen isotopic composition of carbon (δ¹³C) and nitrogen (δ¹⁵N). Most of the data for the ages of the remains corresponded to the cooler and damper periods described over the past 1000 years. Of the studied samples, the greatest number of remains corresponded to the Spörer (1400–1570), Dalton (1790–1830) and Wolf minima (1280–1350). One sample studied falls within the Maunder minimum (1645–1715). It can be assumed that these minima are connected with a reduced production of food and fodder, that may have initiated famines, epidemics and armed conflicts. Individual climatic minima showed positive correlations between δ¹³C and δ¹⁵N values, indicating that the individuals studied consumed complementary plant or animal diets to different degrees. The elevated δ¹⁵N values in our studied samples compared to the skeletal compositions of the population of the La Tène period (380 – 150 BC) and Germanic inhabitants in the territory of Bohemia (5th–6th centuries AD) and Great Moravia (9th–early 10th centuries AD) might reflect the effect of greater consumption of animal proteins or the proteins of omnivorous animals and fish, which compensated for the lack of plant foodstuffs during the colder periods. The isotopic composition of carbon and nitrogen of the bone collagen for the Spörer and Dalton minima differs from the Wolf minimum. The younger minima show higher δ¹⁵N values for a given δ¹³C value.