Bioaccumulation of metals in timber and edible fruit trees growing on reclaimed coal mine overburden dumps

A field study was carried out (IB-valley areas, Mahanadi Coalfields Limited) to assess the bioaccumulation of heavy metals in the tree species, changes in physicochemical and nutritional properties of mine soils, and bioavailability of metals. Only limited amount of topsoil was added in the plantation pits in the ratio of 1:4 (topsoil: weathered mine spoils), which significantly improved pH and fertility. Out of the six analysed metals, the highest concentration was found for Fe followed by Mn>Zn>Cu>Cd>Ni in mine soils. Metal accumulation and bioconcentration factor (BCF) for each metal were calculated for edible fruit (Mangifera indica, Anacardium occidentale, Psidium guajava, Artocarpus heterophyllus and Syzygium cumini) and timber trees (Acacia mangium, Eucalyptus spp., Techtona grandis and Gravellia robusta). Higher metal accumulations were observed in edible fruit trees than control plants growing in garden soil. Significant variations of metal accumulations were observed amongst timber tree species with higher BCF values. Present study suggested that in spite of addition of topsoil, no significant improvement was observed for the bioavailable metal concentration in the mine soils. Additional care should be undertaken, if edible fruit trees are considered for afforestation of coal mine spoils.