Radial distributions of Pb in stems of 6-year-old spruce trees (Picea abies (L.) Karst.) grown for 2 years in Pb-contaminated soil

Concentrations and total quantities of Ph in annual growth rings of B-year-old Picea abies trees were determined after two years of growth in Pb-contaminated soil. Xylem rings grown after Pb addition to the soil did not show highest Pb concentrations. Peak concentrations of Pb were found in inner, older rings. Radial distribution patterns of total Pb quantities in the rings were different from those of Pb concentrations in the rings. Relatively small quantities were found near the pith and in the outermost rings whereas larger amounts occurred in rings grown in the years just before or after the Pb treatment started. The results were compared to data of a previous harvest of spruce trees from the same experiment after one year of treatment. Radial distributions of Pb concentrations did not change in the period of one year between the first and the second harvest but concentration levels varied. The radial distributions of Pb concentrations were no chronological records of temporal variations in soil Pb levels. Neither concentrations nor quantities of Pb in growth rings were reliable indicators of the year when Pb was added to the soil. The results question the use of such data for biomonitoring of historical changes in environmental Ph pollution levels.