Bioaccumulation of heavy metals by Dyera costulata cultivated in sewage sludge contaminated soil
High concentrations of heavy metals are harmful to plants, animals and humans and their potential accumulation in human tissues and bio-magnification through the food chain cause serious health hazards. An experiment was conducted in the glasshouse to evaluate the potential of Dyera costulata as a bioaccumulator to absorb heavy metals from sewage sludge contaminated soils. D. costulata seedlings were planted in the following growth media: T0 (control soil), T1 (100% sludge), T2 (80% sludge + 20% soil), T3 (60% sludge + 40% soil), T4 (40% sludge + 60% soil) and T5 (20% sludge + 80% soil). T4 showed the best growth performance in terms of height, basal diameter and number of leaves. The maximum reduction of Cd, Cr and Pb was found in the 100% sludge treatment. Zn, Cd, Ni and Cr were highly concentrated in the leaves, while Pb accumulated mainly in the stems. D. costulata showed high potential to retain high amounts of Zn, Ni and Cr in the leaves and Pb in the stems. The species had high translocation factor (TF) and low bioconcentration factor (BCF) values in the soil at higher metal concentrations as well as it was able to tolerate and accumulate high concentrations of Zn, Cd, Ni, Cr and Pb. It means that, this species is a good accumulator of heavy metals and can be considered as a potential bioaccumulator species.
Key words: Phytoremediation, Dyera costulata, heavy metals, sewage sludge.