Effects of a long-term heavy-metal pollution on Scots pine forests

The major source of Cu and Ni emissions in Finland is a Cu-Ni smelter at Harjavalta. The mean, 10-year Cu:Ni ratio of emissions derived from smelting activities is about 3:1. However, the corresponding ratio in the organic layer in an adjacent Scots pine stand is 12:1, suggesting that Cu is retained more efficiently than Ni in the surface soil. The experimentally estimated rate of Cu uptake by the roots of pine seedlings cultivated in smelter-polluted soil was higher than the corresponding Ni uptake rate, but Ni transport from the roots to the shoot was more efficient than that of Cu. This is in agreement with an exposure experiment in which the lethal metal threshold in pine roots was found to be much lower for Ni (less than 100 mg kg(-1)) than for Cu (less than 1000 mg kg(-1)). The overall metal uptake rates of the pine seedlings were relatively low and had no reducing effect on the metal concentrations in the soil.