Identification of metal tolerant plant species for sustainable phytomanagement of abandoned red mud dumps

Abstract

Bauxite residue (red mud) generation is increasing largely following the high demand for aluminium worldwide. Thus to manage the residue, different phytotechnologies need to be developed which offer sustainable and eco-friendly options. Considering this, the present study was conducted to assess the phenotype and distribution of metals in herbaceous species at forest (FS) and abandoned red mud dumping (RMD) sites. The study also encompassed the categorization of dominant species in relation to their metal tolerance capabilities at RMD site. Soil at RMD site was marked by high alkalinity, salinity and poor nutrient status. Also, contents of Fe, Zn, Cu, Mg, Mn, Ni, Co, Cr, Cd and Pb in soil at RMD site were higher, but their phytoavailabilties were less as compared to FS site. Herbaceous community at both the sites were dominated by Poaceae and Asteraceae families. Biological spectrum of vegetation at FS site showed predominance of therophytes followed by chamaephytes and hemicryptophytes, whereas RMD site showed preponderance of therophytes followed by hemicryptophytes and chamaephytes. Based on metal tolerance index, 51.4, 10.8 and 37.8% of herbaceous species exhibited sensitive, moderate and high metal tolerant behaviour, respectively. Dominant species e.g. Brachiaria mutica, Cynodon dactylon, Dactyloctenium aegyptium, Digitaria ischaemum, Digitaria longiflora, Eragrostis cynosuroides, Launaea asplenifolia, Parthenium hysterophorus, Sporobolus diander and Stylosanthes scabra with high metal tolerance capabilities indicated their tendency towards a definite selection strategy in response to altered soil properties at RMD site. The study thus offers a potential avenue towards phytomanagement of abandoned red mud dumps by reclamation using dominant and metal tolerant plant species.