Thallium Speciation and Extractability in a Thallium- and Arsenic-Rich Soil Developed from Mineralized Carbonate Rock

• Published in: Environmental science & technology 2015-05, Vol.49 (9), p.5390-5398
• Main Authors: Voegelin, Andreas, Pfenninger, Numa, Petrikis, Julia, Majzlan, Juraj, Plötze, Michael, Senn, Anna-Caterina, Mangold, Stefan, Steininger, Ralph, Göttlicher, Jörg
• Format: Article
• Language: English
• Subjects: Acids - chemistry; Arsenic - analysis; Carbonates - analysis; Chemical elements; Environmental Pollution - analysis; Ferric Compounds - chemistry; Geologic Sediments - chemistry; Hydrogen-Ion Concentration; Mass spectrometry; Minerals; Minerals - chemistry; Oxalates - chemistry; Soil - chemistry; Soil contamination; Soil Pollutants - analysis; Spectrometry, X-Ray Emission; Spectrum analysis; Sulfates - chemistry; Switzerland; Thallium - analysis; X-Ray Absorption Spectroscopy
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.5b00629

We investigated the speciation and extractability of Tl in soil developed from mineralized carbonate rock. Total Tl concentrations in topsoil (0–20 cm) of 100–1000 mg/kg are observed in the most affected area, subsoil concentrations of up to 6000 mg/kg Tl in soil horizons containing weathered ore fragments. Using synchrotron-based microfocused X-ray fluorescence spectrometry (μ-XRF) and X-ray absorption spectroscopy (μ-XAS) at the Tl L3-edge, partly Tl­(I)-substituted jarosite and avicennite (Tl2O3) were identified as Tl-bearing secondary minerals formed by the weathering of a Tl–As–Fe-sulfide mineralization hosted in the carbonate rock from which the soil developed. Further evidence was found for the sequestration of Tl­(III) into Mn-oxides and the uptake of Tl­(I) by illite. Quantification of the fractions of Tl­(III), Tl­(I)-jarosite and Tl­(I)-illite in bulk samples based on XAS indicated that Tl­(I) uptake by illite was the dominant retention mechanism in topsoil materials. Oxidative Tl­(III)­uptake into Mn-oxides was less relevant, probably because the Tl loadings of the soil exceeded the capacity of this uptake mechanism. The concentrations of Tl in 10 mM CaCl2-extracts increased with increasing soil Tl contents and decreasing soil pH, but did not exhibit drastic variations as a function of Tl speciation. With respect to Tl in contaminated soils, this study provides first direct spectroscopic evidence for Tl­(I) uptake by illite and indicates the need for further studies on the sorption of Tl to clay minerals and Mn-oxides and its impact on Tl solubility in soils.