Detoxification and amelioration of heavy-metal contaminated forest soils by means of liming and fertilisation.

Four experiments were established in 1992 in Scots pine stands (Pinus sylvestris L.) on relatively infertile sites at distances of 0.5, 2, 4 and 8 km to the south-east of the Cu-Ni smelter at Harjavalta, south-west Finland, in order to investigate the effects of liming, correction fertiliser and site-specific fertiliser treatments on heavy metal (Cu, Ni) and macronutrient (Ca, Mg, K) availability in the organic layer. The organic layer samples were analysed for total, plant-available (BaCl(2)+EDTA) and water-extractable Ca, Mg, K, Cu and Ni. A high proportion of the Cu and Ni at 0.5 km was in a non-toxic, immobilised form. Liming had only a relatively small reducing effect on free and exchangeable Cu and Ni concentrations at 0.5 km. The lack of pH increase following liming may be due to the precipitation of Fe, present in very high concentrations close to the smelter, as Fe(OH)(3), resulting in the loss of neutralising bicarbonate and hydroxyl ions, but the release of Ca and Mg. Liming strongly increased Ca and Mg availability. The correction fertiliser had no effect on Ca or K availability at any of the sites.