Our new study reveals that the health risk from arsenic-contaminated soil and mine waste is not just about how much arsenic is present—but what form it takes. We tested 16 environmentally important arsenic minerals using a method that mimics human digestion. Results showed bioaccessibility ranged from nearly zero to 100%, depending on the mineral. When mixed with soil, arsenic from low-solubility minerals became even less bioaccessible. These findings highlight the crucial role of mineralogy in assessing arsenic exposure risks.

Drahota P., Ettler V., Košek F. (2025): Arsenic bioaccessibility in environmentally important arsenic minerals. Journal of Hazardous Materials 485, 136838. (DOI)

Skeletal remains collected from 46 Bohemian and Moravian ossuaries were of an age corresponding to cold climatic fluctuations in the past millennium. It seems that climatic events, associated with limited solar activity, influenced the production of plant food. The values of δ¹⁵N and δ¹³C have a linera dependence, indicating a predominant sources of protenins. Simultaneously, the compositions of the bone collagen exhibited differences in the isotopic compositions of C and N, which could be caused by the better management in smaller municipalities and as a consequence of the availability of plant protenins with a higher content of the heavier isotopes of nitrogen or greater availability of animal proteins.

Smrčka V., Mihaljevič M. (2024): Depositing sskeletal remains in Czech and Moravian ossuaries and associated climatic variations. Radiocarbon 66, 552-567. (DOI)

For the first time, copper isotopes (expressed as δ⁶⁵Cu) wer used as indicators of reactions occurring during the Cu-ore heap leaching, an in situ technological process used for extraction of this strategic metal. In comparison with unleached ore (average δ⁶⁵Cu  -1.47‰), leached ores exhibit lighter isotopic values (average δ⁶⁵Cu -6.01‰) and enrichment of the leachate in heavier ⁶⁵Cu isotope indicating a dissolution of primary Cu-bearing minerals along with an oxidation process. Our results, based on combined measurements of Cu isotopes and mineralogical investigation with geochemical modelling, can be used as analogy of Cu leaching in gossans. 

Sracek O., Ettler V., Mihaljevič M., Kříbek B., Mapani B., Penížek V., Zádorová T., Vaněk A. (2024): Identification of processes in Cu-ore heap leaching using Cu isotopes and leachate chemistry at Tschudi mine, northern Namibia. Hydrometallurgy 228, 106356. (DOI)

The significant release of arsenic observed from ferric arsenate minerals in the presence of elevated phosphate levels underscores the complexity of their stability in natural environments. Our findings highlight the need to reconsider phosphate treatments in extraction procedures involving ferric arsenates, emphasizing the importance of cautious application in managing polymetallic mine wastes. For sustainable land management, minimizing long-term phosphate additions to arsenic-contaminated soils and mine tailings containing ferric arsenates is crucial to mitigate As(V) export into surface waters and groundwater.

Petra Stubbe (Venhauerova), Irena Matulková, Christian Mikutta, Petr Drahota (2024): Dissolved phosphate decreases the stability of amorphous ferric arsenate and nano-crystalline yukonite. Journal of Hazardous Materials 471, 134374. (DOI)

Wastewater treatment plants are an important source of phosphorus to the environment. They are estimated to bring between 25 and 45 % of total phosphorus in freshwaters. This study describes how discharged phosphate releases arsenic from streambed sediments into freshwaters. After seven years, the concentration of total As in the streambed sediment below the wastewater treatment plant decreased by 25 % due competitive desorption of arsenate by phosphate.

Petra Venhauerova, Petr Drahota, Ladislav Strnad, Šárka Matoušková (2022): Effects of a point source of phosphorus on the arsenic mobility and transport in a small fluvial system. Environmental Pollution 315, 120477. (DOI)

This study explores the oxidation of arsenopyrite (FeAsS) and löllingite (FeAs₂) at high relative humidity (RH: 75%-100%). Long-term oxidation (40 months) experiments show that oxidation of arsenopyrite and löllingite led to formation of different assemblages of secondary phases. Arsenopyrite oxidized to poorly-crystalline ferric arsenate, while löllingite oxidized to scorodite (FeAsO₄·2H₂O) and arsenolite (As₂O₃). Our results showed that the exposure of arsenopyrite and löllingite to different RH levels significantly influenced the amounts of newly formed phases. The major environmental impact of sulfide weathering occurs in well aerated environments characterized by high humidity – such as underground workings and some unsaturated mine wastes and tailings deposits.

Drahota, P., Ettler, V., Culka, A., Rohovec, J., Jedlička, R. (2022): Effect of relative humidity on oxidation products of arsenopyrite and löllingite. Chemical Geology 605, 120945. (DOI)

Cobalt is one of the most important critical metals which could be potentially extracted from the old metallurgical slags in the Zambian Copperbelt. The slags from Luanshya, the oldest mining and smelting site in the Copperbelt, contain up to 5990 ppm Co (median: 2370 ppm). The detailed mineralogical investigation combined with the sulfuric acid leaching simulating hydrometallurgical recovery indicated that up to 67% of Co can be extracted from slag in a short period of time (24 h). However, despite the dramatic increase of Co prices on the global market, its recovery from the Luanshya slags appears to be non-economical due to the high costs of the mechanical and chemical processing of the slag materials. The paper is freely available via open access:

Ettler V., Mihaljevič M., Drahota P., Kříbek B., Nyambe I., Vaněk A., Penížek V., Sracek O., Natherová V. (2022): Cobalt-bearing copper slags from Luanshya (Zambian Copperbelt): Mineralogy, geochemistry, and potential recovery of critical metals. Journal of Geochemical Exploration 237, 106987. (DOI)

We used an in situ experimental technique with double nylon experimental bags  to study the effect of low-cost organic materials (sawdust, wood cubes and hemp shives) on As sulfidation in three naturally As-enriched wetland soils. After 15 months of in situ incubation, all of the organic materials were covered by yellow-black mineral accumulations, dominantly composed of crystalline As₄S₄ polymorphs (realgar and bonazziite) and reactive Fe(II) sulfides (probably mackinawite). Our findings suggest an authigenic formation of AsS minerals in strongly reducing conditions of experimental bags by a combination of reduced exchange of solutes through the pores of the bag and comparatively fast microbial production of dissolved sulfide. Arsenic sulfide formation, as an effective treatment mechanism for natural and human-constructed wetlands, appears to be favored for As(III)-rich waters with a low Fe(II)/As(III) molar ratio, preventing the consumption of dissolved As and sulfide by their preferential incorporation into natural organic matter, and newly-formed Fe(II) sulfides, respectively.

Peřestá, M., Drahota, P., Culka, A., Matoušek, T., Mihaljevič, M. (2022): Impact of organic matter on As sulfidation in wetlands: An in situ experiment. Science of the Total Environment 819, 152008. (DOI)

We compared analogous healthy topsoils and ones burned by fires of different temperatures for their elemental and isotopic Pb content. The fires only affected the top 5 cm of the soil. We found that soils affected by low-temperature fires had increased Pb compared to healthy soils. The accumulation of Pb was not observed in the soils exposed to higher temperatures. The same results were found in ash. Lead isotopic ratios were affected by the fires. These increased in soils affected by higher temperatures but didn’t change with the low temperatures. We proposed that the temperature dependence is due to anthropogenic Pb (²⁰⁶Pb/²⁰⁷Pb < 1.16) volatilizing at lower temperatures than geogenic Pb (²⁰⁶Pb/²⁰⁷Pb > 1.19). This work suggests that it may be possible to determine the temperature of a forest fire from the Pb isotopic signatures of the burned materials.

Baieta R., Vieira A.M.D, Vaňková M., Mihaljevič M. (2022): Effects of forest fires on soil lead elemental contents and isotopic ratios. Geoderma 414, 115760. (DOI)

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. For this purpose, new wildfire-simulating setups were introduced. Laboratory single-step combustion experiments (250–850 °C) and experiments with a continuous temperature increase and online ICP-OES detection (25–750 °C) were coupled with mineralogical investigations of the soils, ashes, and aerosols. The results indicate that metals are dominantly concentrating in the ash residue, and part of As is remobilized depending on temperature. Therefore, the active and abandoned mining and smelting sites, especially those highly enriched in As, should be protected against wildfires, which can be responsible for substantial As re-emissions.

Tuhý M., Ettler V., Rohovec J., Matoušková Š., Mihaljevič M., Kříbek B., Mapani B. (2021): Metal(loid)s remobilization and mineralogical transformations in smelter-polluted savanna soils under simulated wildfire conditions. Journal of Environmental Management 293, 112899. (DOI)