Efficacy of biochar on the phytoremediation potential of Tithonia diversifolia on spent oil-contaminated soil

The application of biochar has gained attention as a simple, affordable and sustainable strategy for the remediation of contaminated soils. However, the phytoremediation potential of certain plants and interactions with biochar are necessary to achieve effective environmental clean-up. This study evaluated the influence of biochar on the remediation potential of Tithonia diversifolia grown in spent oil-contaminated soil. T. diversifolia was grown for six weeks in spent oil-contaminated soil amended with rice biochar (RB), sorghum biochar (SB) and standard biochar (StB). Four different application rates (0, 1, 2 and 3% w/w) were used. The heavy metals studied included copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd) and chromium (Cr). Biochar treatments was assessed using one-way analysis of variance (ANOVA) and significant differences in soil properties, plant growth, and heavy metal content were further investigated with Duncan’s multiple range test (DMRT). All statistical analyses were conducted using SPSS 21.0 statistical package. The results of this study showed that biochar enhanced the biomass of T. diversifolia particularly by RB treatment. Also, biochar influence the bioavailability of heavy metals in polluted soil. The specific biochar relation with T. diversifolia affect its status from a phytoextractor to a phytostabilizer for specific heavy metal. On the other hand, SB changed Cu-phytostabilizing T. diversifolia to a Cu-phytoextracting plant. Generally, the phytoextraction and phytostabilization capacities of T. diversifolia is dependent on the biochar features. These features are influenced by the feedstock, the pollutant and soil type. Hence, the need for further studies on the interaction of T. diversifolia and biochar for soil remediation. Feasible long term field studies and monitoring strategies can be conducted on varied biochar types in relation to plants remediating potential for specific heavy metal. This will provide a valuable insight on sustainable biochar application for remediation of heavy metal contaminated soil.