Green synthesised iron oxide nanoparticles decorated on biochar for enhanced natural attenuation in simulated petroleum compromised soil

Nanobioremediation is an emerging technique for pollution management. This study aimed to enhance the natural attenuation process during remediation of petroleum polluted soil using a nanocomposite consisting of green synthesised iron oxide nanoparticles decorated on cow bone-derived biochar. The biochar used was produced via slow pyrolysis at 500 °C under low oxygen conditions while the iron oxide nanoparticles were synthesised using extracts from leaves of the pea eggplant ( Solanum torvum ). The iron oxide-biochar nanocomposite (BCNP) was applied to soil in microcosms at 10% w/w and 15% w/w amendment levels, and the set-ups were monitored for 60 days. At the end of the study, the total cultivable heterotrophic bacterial abundance in the BCNP amended soils were 7.37–8.92 times greater than the observed abundance in the biochar controls. Similarly, total petroleum hydrocarbon removal levels were 28.4 and 26.2% greater (at 10% w/w and 15% w/w BCNP, respectively) than obtained with the plain biochar controls. Klebsiella pneumoniae , Pseudomonas spp. and Bacillus spp. were the predominant cultivable heterotrophic bacterial isolates while Pseudomonas spp., Acinetobacter spp. and Enterobacter spp. dominated amongst the cultivable hydrocarbon utilising bacteria. Metagenomic analysis revealed that the initial dominance of Proteobacteria and Acidobacteria phyla at the onset of the study gave way to the dominance of the Proteobacteria as the study proceeded with Pseudomonas spp. dominating at the genus taxonomic rank. The iron oxide nanoparticle decorated biochar proved effective in boosting natural attenuation in petroleum-compromised soil.