LONG-TERM CORRELATIONS BETWEEN MINING ACTIVITY AND LEVELS OF LEAD AND CADMIUM IN TREE-RINGS OF EASTERN RED-CEDAR

Growth increments of eastern red-cedar (Juniperus virginiana L.) from sites in the Pb mining district of southeast Missouri were subjected to multielemental analysis. Three chronologies, two of Pb and one of Cd, were constructed from heartwood growth increments of 27 trees on sites in the mining district and on control sites. No significant increases in Pb and Cd were found in growth increments of trees on control sites. Lead in the xylem of trees growing in acid soils of the mining district increased from 3.1-mu-mol kg-1 in growth increments formed before 1900 to 7.8-mu-mol kg-1 in increments formed after 1900. Cadmium was detected in 46% of the wood formed after 1900 vs. 3% of the wood formed before 1900. Lead and Cd were found only in wood grown on acid soils (pH < 4.6) and not in wood grown in more basic soils. Lead and Cd concentrations in growth increments are found to be highly correlate with Pb production. Lead in sapwood was also found to correlate with soil pH on acid sites in both the mining district and in the control sites.