Thallium in Technosols from Allchar (North Macedonia): Isotopic and speciation insights

• Published in: Environmental pollution (1987) Vol. 357; p. 124413
• Main Authors: Vaněk, Aleš, Đorđević, Tamara, Mihaljevič, Martin, Vaňková, Maria, Fizková, Karolína, Zádorová, Tereza, Vokurková, Petra, Galušková, Ivana, Penížek, Vít, Drábek, Ondřej, Tasev, Goran, Serafimovski, Todor, Boev, Ivan, Boev, Blažo
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15.09.2024
• Subjects: Fractionation; Isotope; Mining; Oxide; Soil; Waste; Mining; Oxide; Soil; Fractionation; Isotope; Waste
• ISSN: 0269-7491; 1873-6424; 1873-6424
• DOI: 10.1016/j.envpol.2024.124413

Allchar (North Macedonia) mining area is known for anomalous background Tl concentrations. In this study, we combine accurate detection of Tl stable isotope ratios with data on mineralogy/speciation and chemical extraction of Tl in Tl-contaminated Technosol profiles. We demonstrate that Tl in the studied soils varies significantly in both concentration (500 mg/kg-18 g/kg) and isotopic composition (−1.6 and +3.2 of ε205Tl, a ∼0.5‰ spread), which is due to changes in the phase chemistry and/or mineralogy of Tl. Moreover, the observed 205Tl/203Tl ratios do not reflect the extent to which individual soils undergo Tl isotopic fractionation during mineral weathering and soil formation. Clearly, they reflect the initial isotopic signal(s) of the primary ore or ore minerals, and thus, the general history or type of their genesis. As the Tl carriers, various types of Tl–Me-arsenates, mixtures of jarosite and dorallcharite and minor Mn-oxides predominated. We revealed intense adsorption of Tl by the identified Mn-oxides (≤6.7 at.%). It is hypothesized that these phases are of key importance in the fractionation of Tl isotopes, meaning at this type of secondary oxide-soil solution interface. However, model studies involving primary/secondary components (sulfides, sulfates, oxides and arsenates) are required to understand the mechanisms that may lead to post-depositional Tl isotopic redistribution in soils, as well as Tl isotope systematics in mining wastes in general. [Display omitted] •Thallium concentrations in soils are between 500 mg/kg and 18 g/kg.•205Tl/203Tl soil data reflect changes in phase chemistry/mineralogy.•205Tl/203Tl soil data reflect initial isotopic signals related to ore genesis.•205Tl/203Tl soil data do not show post-depositional isotopic fractionation.•Intense Tl uptake by Mn-oxides (≤6.7 at.%).