Bioaccumulation of heavy metals in plant leaves from Yan׳an city of the Loess Plateau, China.

Urban plants are capable of reducing environmental pollutions through bioaccumulation contaminants in their tissues. The accumulation of heavy metals (Pb, Cu, Cd, Cr, and Zn) in leaves of nine tree species and five shrub species from Yan׳an city of China were investigated, and total metal accumulation capacities of different plants were evaluated using the metal accumulation index (MAI). The results indicated that plants in polluted environments are enriched in heavy metals relative to those in pristine environments, this is mainly caused by traffic emissions and coal combustion. Species with the highest accumulation of a single metal did not have the highest total metal accumulation capacity, the MAI should be an important indicator for tree species selection in phytoextraction and urban greening. Considering total accumulation capacities, Sabina chinensis, Juniperus formosana, Ailanthus altissima and Salix matsudana var. matsudana could be widely used in the Loess Plateau.