Keywords: Betula pendula, siver birch, bleeding sap, cadmium, copper, heavy metals, leaf age, manganese, zinc, environmental pollution, soil contamination
Bleeding sap and leaves of silver birch (Betula pendula) as bioindicators of metal contaminated soils
Bleeding sap of Betula pendula contained high levels of manganese on soils near ore outcrops and on acid soils, whereas high zinc levels were restricted to metal-mining and metal-smelting areas. The relationships between metal contents of bleeding sap and those of the soils were dependent on the kind of chemical soil extraction. Copper and zinc sap levels had a significantly positive correlation with the aqua regia soil extract, iron and manganese with the CaCl2-extract, and cadmium with the NH4-acetate soil extract. Metal contents of mature leaves were highest in autumn and all, except cadmium, were related in a similar metal-specific way to the same chemical soil extracts as the bleeding sap. Lead levels of sap and leaves had no consistent correlation with type of soil extract. The timing of collection and the advantages of the analysis of bleeding sap versus mature leaves are discussed.