Heavy metal fractions in rhizosphere sediment vis-à-vis accumulation in Phoenix paludosa (Roxb.) mangrove plants at Dhamra Estuary of India: assessing phytoremediation potential.

Total and sequentially extracted fractions (exchangeable, bound to carbonate, bound to iron and manganese oxides, bound to organic matter and residual) of eight heavy metals (Cu, Mn, Zn, Ni, Fe, Cr, Cd and Pb) were estimated in rhizosphere sediment along with their accumulation in roots and leaves of Phoenix paludosa plants at Dhamra estuary. The Cu, Mn, Zn, Ni, Fe, Cr, Cd and Pb content in rhizosphere sediments were 162.2, 563.3, 289.1, 228.8, 31,524.3, 475.5, 8.5 and 256.8 mg/kg, respectively. For almost all the heavy metals, sequential extraction estimation showed residual>bound to iron and manganese>bound to organic matter>bound to carbonate>exchangeable fractions. Exceptionally very high residual Cr (77.36%) and organic matter-bound Cd fraction (41.10%) highlighted the sedimentary mine run-off and industrial activities as their main source of pollution, respectively. Phoenix paludosa exhibited maximum bio-concentration (0.34), bio-accumulation (0.51) and translocation (0.50) factor for Cd. The primary results revealed the phyto-accumulation behaviour of different heavy metals in Phoenix paludosa and showed its relatively higher remediation potential for Cd and Cr pollution. In view of the above facts, heavy metals-polluted estuarine sites can be remediated through afforestation of Phoenix paludosa plant species. [ABSTRACT FROM AUTHOR]