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)

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)

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)

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

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)

The findings of this study indicated that the historical mining village of Kaňk is highly contaminated by As, Cu, Pb, and Zn, of which As is the most significant contaminant. Despite the high concencentration of As in mining wastes (∼1.15 wt.%), urban soils (∼0.3 wt.%), and road dusts (∼ 440 mg/kg), risk was associated only with mining waste and contaminated soil material via oral exposure (not the inhalation pathway)

Drahota P., Raus K., Rychlíková E., Rohovec J. (2018): Bioaccessibility of As, Cu, Pb, and Zn in mine waste, urban soil, and road dust in the historical mining village of Kaňk, Czech Republic. Environmental Geochemistry and Health 40, 1495-1512. (DOI)