Assessment of native plant species for phytoremediation of heavy metals growing in the vicinity of NTPC sites, Kahalgaon, India.

The present investigation was carried out to screen native plants growing in fly ash (FA) contaminated areas near National Thermal Power Corporation (NTPC), Kahalgaon, Bihar, India with a view to using them for the eco-restoration of the area. A total number of 30 plant species (5 aquatic and 25 terrestrial including 6 ferns) were collected and their diversity status and dominance were also studied. After screening of dominant species at highly polluted site, 8 terrestrial and 5 aquatic plants were analyzed for heavy metals (Fe, Zn, Cu, Ni, Si, Al, Pb, Cr, and Cd). Differential accumulations of various heavy metals by different species of plants were observed. Typha latifolia was found to be most efficient metal accumulator of Fe (927), Cu (58), Zn (87), Ni (57), Al (67), Cd (95), and Pb (69), and Azolla pinnata as Cr (93) hyper-accumulator among aquatic species in µg g(-1). In terrestrial species the maximum levels of Fe (998), Zn (81), Ni (93), Al (121), and Si (156) were found in Croton bonplandium. However, there was high spatial variability in total metal accumulation in different species indicated by coefficient of variation (CV%). These results suggest that various aquatic, some dominant terrestrial plants including fern species may be used in a synergistic way to remediate and restore the FA contaminated wastelands.

Bioconcentration and phytotoxicity of chromium in Eichhornia crassipes.

Physico-chemical parameter and metal concentration in effluents of two industries i.e. Tannery industry, Jajmau, Kanpur and Electroplating industry, Scooter India Limited (SIL), Lucknow were determined to assess the toxicity of chromium. Metal accumulation in Eichhomia crassipes growing in these contaminated sites were also determined. For laboratory toxicity testing the plants were exposed to nutrient solution containing Cr concentration ranging from 0.01-10 microg ml(-1) for 24-96 hr. Accumulation of chromium was observed to be dependent on its concentration and time of exposure and was greater in roots (789.3 mg g(-1) d.wt.) than in leaves (335.6 mg g(-1) d.wt.) after 96 hrat 10 microg ml(-1) concentration. Under field conditions the accumulation of Cr was 1258 and 733.3 in roots and 94 and 53 microg g(-1) d.wt. in leaves of E. crassipes growing in Jajmau, Kanpur tanning industry and SIL effluents, respectively. It was found that lower doses (0.01-0.1 microg ml(-1)) of chromium had stimulatory effect on various metabolic activities in plants including chlorophyll a, b and total chlorophyll, protein, nitrate reductase and mitotic index. Whereas higher doses of chromium had inhibitory effect. The carotenoid content and number of micronuclei was found directly proportional to the concentration of chromium and increased with increase in concentration of chromium to which plants were exposed. It may be concluded from the present study that E. crassipes is tolerant to the elevated Cr concentration as there is no inhibition of chlorophyll and carotenoid up to 0.1 microg ml(-1) at 24 and 48 hr exhibiting phytotoxicity at higher concentration. Therefore, E. crassipes may be used as bioassay for biomonitoring and control of Cr pollution in the environment.