Phytochelatins are bioindicators of atmospheric metal exposure via direct foliar uptake in trees near Sudbury, Ontario Canada

Plants produce phytochelatins in response to copper and nickel, the primary metal pollutants emitted by the dominant smelting operation in Sudbury. Co pper and nickel concentrations in soils decline sharply with distance from this facility, primarily as a result of early smelting practices. Phytochel atin concentrations in Sudbury-area trees, however, do not correlate with m etal levels in soils. Rather, phytochelatin production in tree leaves is dr iven by metals currently released to the atmosphere through the 381 m emiss ions stack. Phytochelatin concentrations in the foliage of three tree speci es growing in situ are highest 20-30 km from the stack, correlated with max imum acid-leachable concentrations of deposited copper and nickel. Similar results observed in potted trees placed adjacent to indigenous trees confir m that aerially deposited metals are the source of current metal stress pat terns. The addition of peat moss "filters" to potted soils did not alter th is response, indicating that direct foliar metal uptake is responsible.