Lithogenic thallium behavior in soils with different land use |
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| Authors: | Aleš Vaněk Vladislav Chrastný Martin Mihaljevi? Petr Drahota Tomáš Grygar Michael Komárek |
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| Institution: | 1. Department of Soil Science and Soil Protection, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Praha 6, Czech Republic;2. Department of Applied Chemistry, University of South Bohemia, Studentská 13, 370 05 ?eské Budějovice, Czech Republic;3. Institute of Geochemistry, Mineralogy and Mineral Resources, Charles University, Albertov 6, 128 43 Praha 2, Czech Republic;4. Institute of Inorganic Chemistry, Analytical Laboratory, Academy of Sciences of the Czech Republic, v.v.i, 250 68 ?e? u Prahy, Czech Republic;5. Department of Agro-Environmental Chemistry and Plant Nutrition, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Praha 6, Czech Republic |
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| Abstract: | In order to evaluate the effect of different land use on lithogenic Tl geochemistry, two forest and grassland soils developed on an identical Tl-rich substrate were examined. For this purpose a complex soil-plant investigation supplemented by mineralogical methods was performed. The modified BCR sequential extraction combined with X-ray diffraction analysis (XRD) and voltammetry of microparticles (VMP) were performed for a detailed insight on lithogenic Tl speciation and availability in both contrasting soils. It was revealed that soil forming processes like bioturbation and probably dust deposition may influence the increased input of lithogenic Tl into the forest floor. Thallium was predominantly bound within the residual fraction (up to 95%) corresponding to primary silicates (mainly orthoclase and muscovite) and probably secondary illite, which were detected by XRD in all studied horizons. Thus, stable silicates can be thought as the phases controlling the solubility of lithogenic Tl in both the forest and grassland soils. The highest portion (~ 5%) of “labile” Tl was found in the organic horizons of the forest soil indicating a distinct role of forest soil organic matter (SOM) on Tl mobilization and availability. Thallium adsorption was dominated by an identified non-crystalline Mn(III,IV) oxide detected by VMP proving thus its strong affinity for Mn oxides in mineral soils. On the contrary, Tl adsorption by more abundant Fe(III) oxides (goethite and ferrihydrite) was evaluated to be negligible. Organically bound Tl in the forest floor was found to be associated with primary SOM corresponding to the raw and partially decomposed litter of Norway spruce (Picea abies L.). Moreover, a relatively high Tl uptake was recorded by this species. In contrast, lithogenic Tl uptake by common grasses like red clover (Trifolium pratense L.) or timothy grass (Phleum pratense L.) seems to be very low. |
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| Keywords: | Thallium Speciation Mn oxide Forest Grassland |
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