Dissolved phosphate decreases the stability of ferric arsenates

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)

Discharged phosphorus releases arsenic from streambed sediments

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)

The effect of different humidity on the oxidation of arsenopyrite and löllingite

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 recovery from Zambian slags

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)

Sulfidation of As in wetland soil – in situ experiment

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)

Do forest fires alter the Pb isotopic composition of topsoils?

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)

Metal(loid)s remobilization from contaminated soils during experimental wildfires

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)

Lead isotopic compositions in La Tène artifacts

The paper presents a geochemical analysis of a remarkable assemblage from the early La Tène period (4th century BCE): the Duchcov hoard found in the late 19th century in north-western Bohemia. More than a thousand pieces of bronze jewellery in a bronze cauldron were deposited in a natural spring. This possibly ritual offering of unknown purpose might have involved a large community whose origin and structure could be discussed using archaeometric data from the hoard. This assemblage offers a unique opportunity to study Iron Age bronze metalworking. The results show that this seemingly homogeneous assemblage contains several chemically distinctive groups that are compatible with the spread of the so-called Duchcov-Münsingen horizon in the 4th century BCE.

Danielisová A., Pajdla P., Bursák D., Strnad L., Trubač J., Kmošek J. (2021): Claiming the land or protecting the goods? The Duchcov hoard in Bohemia as a proxy for ‘Celtic migrations’ in Europe in the 4th century BCE. Journal of Archaeological Science 127, 105314. (DOI)

Looking at a Pb–Zn mining/smelting site in Kabwe (Zambia) using tree rings

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 in abandoned mines

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)