Comparative studies on accumulation of Cr from metal solution and tannery effluent under repeated metal exposure by aquatic plants: its toxic effects.

The present study demonstrates comparison of Cr accumulating potential by the plants of Najas indica Cham. (submerged), Vallisneria spiralis L. (rooted submerged) and Alternanthera sessilis R. Br. (rooted emergent) under repeated metal exposure and its effect on chlorophyll and protein concentrations. These plants were treated with different concentrations of Cr under repeated exposure in controlled laboratory conditions to assess the maximum metal accumulation potential. The plants of V. spiralis accumulated significantly high amount of Cr under laboratory conditions in comparison to N. indica and A. sessilis. The maximum accumulation of 1378, 458 and 201 microg (-1) dw Cr was found in the leaves of V. spiralis. N. indica and A. sessilis, respectively at 8 mg (-1) after 9 day of Cr exposure. These plants have shown a decrease in chlorophyll and protein concentrations with increase in Cr concentrations. In view of high accumulation of Cr in V. spiralis, the plants were treated with different concentrations of tannery effluent collected from Common Effluent Treatment Plant, Unnao (UP). The plants of V. spiralis treated with 100% tannery wastewater showed the maximum accumulation (57.5 microg g(-1) dw) of Cr in the roots after 10 days of exposure. The plants were found effective in removing Cr from solution and tannery effluent.