EXTRACTION OF CD AND PB FROM STEM WOOD OF OAK TREES (QUERCUS-PETRAEA [MATT] LIEBL) WITH VARIOUS SOLUTIONS

Radial distribution of total and of extractable concentrations of Cd a nd Pb in wood of oak trees (Quercus petraea) were investigated. Wood s amples obtained from stem bases of mature trees were extracted with H2 O and 0.01 M solutions of acetic acid, citric acid, CaCl2 and EDTA. Ex tracted quantities were expressed in percent of total concentrations. The Cd extracting efficiency increased in the order H2O < acetic acid < CaCl2 < citric acid < EDTA. With H2O less than 10 %, with EDTA up to 94 % of Cd were extracted. In the case of Pb the order of extracting efficiency was citric acid < CaCl2 < EDTA. Water and acetic acid did n ot mobilize detectable amounts of Pb. In general the extracting effici encies of the solutions were correlated to the complex stability const ants for binding to Cd and Pb. Whereas CaCl2 acted by ion exchange of xylem-bound Cd and Pb, the complexing agents captured cations from the liquid phase and thus affected exchange equilibria between solutions and vessel walls. The results are discussed with respect to binding fo rms and mobility of trace elements in oak wood.