Uptake of trace elements and isotope fractionation of Cu and Zn by birch (Betula pendula) growing on mineralized coal waste pile

Abstract Aims of the present study were to determine the extent of the uptake of selected trace elements by birch (Betula pendula Roth) growing on the partly burnt coal waste pile and to evaluate isotopic fractionation of copper (Cu) zinc (Zn). Substrates, birch sap and leaves were collected in the coal waste pile and in a reference area outside the waste pile. The concentration of trace elements in birch sap and leaves both in birch growing on the coal waste pile and at reference sites increase in the range of U, As, Se > Cd, Mo, Cu > Pb > Ba ≫ Zn. However, the uptake of elements by birch is restricted when concentration of metals in substrates are too high. Compared to the isotopic composition of Cu in waste substrates and soils (δ65Cu = – 0.93 to + 1.49‰), this element in sap and leaves (δ65Cu = – 0.58 to −1.64 and – 0.59 to – 2.35‰, respectively) is depleted in heavy isotope regardless of plant-available concentration of Cu in substrates. Compared to the isotopic composition of Zn in substrates (δ66Zn = – 0.20 to 1.43‰), its isotopic composition in sap and leaves (δ66Zn = – 0.85 to + 1.00 and – 0.21 to + 0.57‰, respectively) is depleted in the heavy isotope only when the plant-available concentration of Zn in the substrate and soil is high (>20 mg kg−1). At low plant-available concentration of Zn no isotopic fractionation or enrichment of Zn in the heavy isotope was recorded.