Root versus canopy uptake of heavy metals by birch in an industrially polluted area: contrasting behaviour of nickel and copper

Patterns of leaf surface contamination and root uptake were similar for nickel and copper; however, nickel but not copper was effectively translocated from roots to shoots and leaves.

Abstract

We investigated root versus canopy uptake of nickel and copper by mountain birch, Betula pubescens subsp. czerepanovi, close to a nickel-copper smelter on the Kola Peninsula, northwest Russia. To distinguish between aerial contamination of leaf surfaces by dust particles and root-derived contamination of leaves by soluble metals, we transplanted seedlings from a control site to clean and metal-contaminated soils and exposed these seedlings both in clean and polluted sites. Patterns of leaf surface contamination and root uptake were similar for nickel and copper; however, nickel but not copper was effectively translocated from roots to shoots and leaves. The majority (80-95%) of nickel and copper found in birch foliage in the heavily contaminated site was due to deposition of dust particles on leaf surfaces; 32-40% of foliar nickel and 9-19% of foliar copper were in water soluble forms. Washing of fresh leaves removed only a minor part of surface contaminants; boiling of unwashed leaves in distilled water for 15 min removed >90% of soluble nickel and copper.