Long-term phytoremediating abilities of Dalbergia sissoo Roxb. (Fabaceae)

Abstract

The boom of tanneries in north India has converted the river Ganga into a waste dumping stream. The tanneries discharge their heavy metal-rich effluents into the river. Tissues of two-year-old tree saplings of Dalbergia sissoo, soil sediments and river water samples were collected from three sites along the river Ganga at Jajmau, Kanpur. Site-1 was located 1 km upstream from the point of discharge of the effluents of the tanneries, Site-2 was close to the source point, and Site-3 was about 1 km downstream from the source point. Accumulation of Cu, Cr and Ni in leaves, bark, wood growth rings, soil sediments and water samples was estimated using an atomic absorption spectrophotometer. The tissues of the two-year-old wood growth rings of D. sissoo accumulated large amounts of Cr, Cu and Ni. The Cr concentration in leaves, bark and wood rings had a strong, positive and linear correlation (r2) with the Cr concentration in soil sediments. The bio-concentration factors (BCFs) of Cr, Cu and Ni were higher than 1 in the wood, bark and leaves at all three selected sites, indicating the strong phytoremediating ability of the tree. The uptake of Cr and Ni was consistent in the bark and wood growth rings of two successive years. Owing to the strong uptake and accumulating abilities of Cr, Cu and Ni as evident from high BCF values and high biomass, we propose D. sissoo as a suitable species for phytoremediation throughout its range of distribution in Africa, Asia and the Americas