HEAVY-METAL CONCENTRATIONS IN PLANTS IN RELATION TO ATMOSPHERIC HEAVY-METAL DEPOSITION

Zinc, Cu, Ph, and Cd concentrations were examined in several plant species and corresponding organic topsoil collected in forest and on ombrotrophic bogs along a temporal (1982-1992) and a spatial (Southern Norway-Central Norway) heavy metal deposition gradient. This allowed relations between metal concentrations in plants, soil/peat, peat, and spatial and temporal changes in atmospheric deposition of heavy metals to be studied. Lead concentrations in plants decreased significantly from 1982 to 1992 both in Southern and Central Norway, while stable levels were observed in surface soil. These observations together with a decrease in atmospheric Pb deposition rates of about 70% both in Southern and Central Norway, suggests that direct atmospheric deposition strongly influenced Pb levels in vegetation. Lead concentrations in vegetation were significantly higher in Southern Norway than in Central Norway both in 1982 and 1992, evidently due to a more than 15 times higher Pb deposition in Southern Norway. Plant concentrations of Zn, Cu, and Cd were significantly higher in Southern Norway than in Central Norway, both in 1982 and 1992, most likely because of higher root uptake in Southern Norway due to distinctly higher surface soil levels of Zn, Cu, and Cd from air pollution in this region. No distinct changes in Zn, Cu, or Cd concentrations in plants, however, where observed from 1982 to 1992, even in Southern Norway where wet deposition of these elements decreased by about 26% (Zn), 40% (Cu), and 51% (Cd) during this period.