Studies on Sophorolipids Induced Phytoremediation of Heavy Metals Contaminated Soil and Stabilization of Phyto Extracted Metal by Biocalcification

Abstract

The aim of the present work was to address the major limitations of phytoremediation. In order to address these limitations, in our first objective two plants BidenspilosaandMedicagosativa screened for the study. Both plants are locally available in Uttarakhand and exhibits great tolerance capability against heavy metals. The second objective of this work was majorly focused on to study the effects of SL in phytoremediation of heavy metal contaminated soil. In this regard, effects of SL on the plant growth, soil physicochemical properties, and phytoremediation efficiency was assessed.The results of this experiment revealed that bioaugmentation of SL in soil increased root, shoot, and dry biomass of B. pilosa, which helped in reducing the metal toxicity.The addition of SL also increased the Cd accumulation (µg pot-1) in B. pilosa, probably due to the increased bioavailability of Cd for plant due to the surfactant action. Assessment of interactive effects of SL and biochar for the phytoremediation of heavy metal contaminated soil was also conducted using response surface methodology. The models generated by CCD of Response surface methodology has R2 values more than 0.9 for Cd uptake in root and shoot as well as 0.85 for soil enzymatic activities. The regression equations showed negative interaction between SL and biochar. newlineLastly, biocalcification was used as a novel approach to overcome the problem of disposal of phyto-extracted biomass. For the biocalcification study, newly isolated urease producing bacterium Advenella sp. AV1 was used. It was observed that using biocalcification process, ash of phytobiomass was co-precipitated with calcite. It was observed that Cd was not increased in carbonate bound fraction but bioavailability of Cd was reduced in the easily available fraction in comparison to ash. Thus, it can be concluded that stabilization of heavy metals in the ash of harvested biomass using biocalcification is a potential approach for the safe disposal of heavy metal laden biomass. newline newline