Assessment of different multipurpose tree species for phytoextraction of lead from lead-contaminated soils

Abstract

Phytoextraction of heavy metals by trees is less hazardous for human beings and animals than their extraction by agricultural crops from the contaminated sites. Therefore, phytoextraction potential of four tree species namely Eucalyptus tereticornis Sm. (eucalyptus), Leucaena leucocephala Lam. de Wit (subabul), Melia azedarach L. (dhrek), and Dalbergia sissoo Roxb. (shisham) to tolerate and extract lead (Pb) from soil at its six applied rates (0, 30, 60, 120, 180, and 240 mg Pb kg − 1 soil) was assessed after 18 months of their growth in a pot experiment. Dry matter (DM) yield of different tree components (stem, leaves, and roots), their Pb concentration, Pb uptake and available Pb in the soil before planting and after harvesting the plants were determined. Contamination indices namely transfer coefficient (TC) or bioaccumulation factor for shoots (BAFshoot), bioaccumulation factor for roots (BAFroot), translocation factor (TF), tolerance index (TI), and the remediation factor (RF) were also determined. The increasing Pb levels led to a significant decrease in total DM yield and in eucalyptus, subabul, dhrek, and shisham, it decreased by 38.9, 34.6, 23.3, and 23.5% at the highest level of applied Pb as compared to control (P ≤ 0.05). The Pb concentration in different plant parts increased significantly with increasing levels of added Pb (P ≤ 0.05). Subabul had significantly highest (0.25 − 100.9 mg pot − 1) removal of Pb at different applied Pb levels and therefore, subabul pots had the lowest amount of available soil Pb after harvesting of plants. Dhrek was observed to have highest (56.4 mg kg − 1 soil) upper critical level of available soil Pb whereas subabul had the greatest Pb extraction capacity from the soil. Contamination indices TF (1.35) and TI (0.88) were highest for dhrek but TC or BAFshoot (3.23), BAFroot (2.66), and RF (7.65%) were highest for subabul. Therefore, subabul can be used for phytoremediation of Pb-contaminated sites due to its more biomass and higher extraction of Pb from soil than the other tree species.