An inductively coupled plasma mass spectrometry (ICP/MS) method was used for the evaluation of thallium transfer from naturally (pedogeochemically) and artificially contaminated soils into rape. Two sets of three different types of top soils (heavy, medium, and light) were used for pot experiments. The first set was collected from areas with high levels of pedogeochemical thallium (0.3, 1.5, and 3.3 mg kg(-1) DM). The second set of three soils with naturally low content of thallium was artificially contaminated with thallium sulfate to achieve five levels of contamination (0, 0.4, 2, 4, and 6 mg kg(-1) DM Tl). The soil samples and the samples of winter and spring rape (straw, seeds) from both sets were collected and analyzed. Plant and soil samples from fields were collected at 42 selected sites situated in South Bohemia and in Czech-Moravian Highlands where higher pedogeochemical content of thallium was expected. More intensive transport (better availability) of Tl was observed in the case of artificially contaminated soils. The physicochemical form and the total content of Tl in soil were found to be the main factors influencing its uptake by plants. The concentration of Tl in rapeseeds in the field samplings was mostly 45% of its content in the particular soil. Nevertheless the uptake of Tl from soils with naturally high pedogeochemical content can be high enough to seriously endanger food chains. These findings are very important because of the high toxicity of Tl and the absence of threshold limits for Tl in soils, agricultural products, feedstuffs, and foodstuffs in most countries including the Czech Republic.
Thallium (Tl) and its compounds are toxic to all organisms. Relatively high levels of thallium of pedogeochemical origin have been found in some areas of the Czech Republic. The contents of .2 mg kg 21 of Tl have been found in aqua regia soil extracts of soils originated from melanocratic porphyric hornblende-biotite granite or from hornblende-biotite granodiorite. The contents of Tl in the range of 0.45-1 mg kg 21 have occurred mainly in soils originated from paragneiss. A detailed study of some of these sites has been made. Content of thallium in soils was determined after extraction
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