Assessment of bioaccumulation of heavy metals by different plant species grown on fly ash dump.

A field experiment was conducted on a 10-hectare area on fly ash dump at Khaperkheda Thermal Power Plant, Nagpur, India, where different ecologically and economically important plant species were planted using bioremediation technology. The technology involves the use of organic amendment and selection of suitable plant species along with site-specific nitrogen-fixing strains of biofertilizers. The study was conducted to find out the metal accumulation potential of different plant species. The total heavy metal contents in fly ash were determined and their relative abundance was found in the order of Fe>Mn>Zn>Cu>Ni>Cr>Pb>Cd. Fly ash samples had acidic pH, low electrical conductivity, low level of organic carbon and trace amounts of N and P. Plantation of divergent species was done on fly ash dump using the bioremediation technique. After 3 years of plantation, luxuriant growth of these species was found covering almost the entire fly ash dump. The results of the metal analysis of these species indicated that iron accumulated to the greatest extent in vegetation followed by Mn, Ni, Zn, Cu, Cr and Pb. Cassia siamea was found to accumulate all metals at higher concentrations compared to other species. The experimental study revealed that C. siamea could be used as a hyper-accumulator plant for bioremediation of fly ash dump.