Nano-enhanced bioremediation of soil co-contaminated with petroleum hydrocarbons and cadmium using Helianthus annuus L. plants

Abstract

Abstract Background Simultaneously removing petroleum hydrocarbons (PHCs) and heavy metals from soil is a challenging task. This study aimed to evaluate the efficacy of green-synthesized nano zero-valent iron (nZVI) particles and a microbial consortium in combination with sunflower ( Helianthus annuus L.) plants for nano-enhanced bioremediation of soil co-contaminated with PHCs and cadmium (Cd). A pot trial was conducted by growing sunflower plants on soil co-contaminated with 6000 mg kg -1 and 30 mg kg -1 of PHCs and Cd, respectively, and nZVI particles and a microbial consortium were added to the soil for plant growth enhancement and pollutants removal. Results The results revealed that the co-contaminated soil caused significant phytotoxicity to sunflower plants. However, the co-application of a microbial consortium and nZVI particles considerably alleviated the phytotoxic impacts of Cd and PHCs on sunflower plants, demonstrating up to 72.7% and 83.5% improvements in plant physiology and growth in contaminated soil, respectively compared to the respective unamended control. Furthermore, the combined application of a microbial consortium and nZVI particles caused 59.4% and 58.6% reduction in bioavailable Cd, and 82.7% and 74.7% decrease in PHCs in planted and unplanted treatments, respectively, with respect to their initially applied concentrations. Conclusion The findings from this study indicate that the integrated application of nZVI particles and a microbial consortium was very effective in improving plant growth, mitigating Cd-accumulation in plants, confirming Cd-immobilization, and removing PHCs from soil, highlighting the potential of nano-enhanced bioremediation as a sustainable solution for the treatment and management of soil co-contaminated with inorganic and organic pollutants.