Korean Journal of Soil Science and Fertilizer 한국토양비료학회 학회지 ISSN:0367-6315(Print) 2288-2162(Online)

Thallium (Tl) is a highly toxic heavy metal that poses a threat to various organisms, including human beings. In plants, Tl is mostly present as the uncomplexed Tl⁺ species, and its uptake by plants follows a similar trend to that of other monovalent ions such as NH₄⁺, Cs⁺, K⁺, Rb⁺, and others. In this study, we investigated the relationships between the Tl concentrations in barley and sunflower and the extractable-Tl concentrations in acidic, neutral, and alkaline soils. We used ammonium and potassium based-inorganic salt extractants, including 1 M NH₄Cl, 1 M (NH₄)₂SO₄, 1 M KCl, and 1 M KNO₃. The Tl concentration in the sunflower tissues harvested from the acidic soil with a treatment of 40 mg Tl kg^-1 was 1,910 mg kg^-1, indicating that sunflower could be considered a Tl-hyperaccumulator plant. Among the extractants, the highest concentration of extractable soil Tl was obtained using 1 M NH₄Cl solution, followed by 1 M (NH₄)₂SO₄, 1 M KCl, and 1 M KNO₃. The Tl concentrations in both plants were well related (R² > 0.910) to the Tl concentrations extractable by ammonium and potassium-based inorganic salts and showed the closest relationship (R² = 0.936 - 0.980) with that extractable by 1 M (NH₄)₂SO₄. Therefore, the ammonium and potassium based-inorganic chemicals can be considered applicable soil Tl extractants in relation to Tl uptake by plants.