Harnessing the sustainable bioremediation potential of leaf litter for polycyclic aromatic hydrocarbon-contaminated soils- A review

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants widely found in contaminated soils due to industrial activities, fossil fuel combustion, and improper waste disposal. Their recalcitrant nature and toxicity pose significant environmental and health risks, making effective and sustainable remediation strategies essential. This review explores the potential of leaf litter—a readily available, biodegradable, and nutrient-rich organic material—as a bio-stimulant for enhancing microbial-mediated PAH degradation in soil environments. Leaf litter not only supplies carbon and nutrients necessary for microbial activity but also serves as a reservoir of phyllosphere-associated microbes, some of which possess hydrocarbon-degrading capabilities. The review examines the chemical and physical properties of PAHs, the microbial mechanisms involved in their degradation, and the environmental factors influencing biodegradation efficiency. Special attention is given to the composition of leaf litter from different plant species, its carbon-to-nitrogen (C/N) ratio, lignin content, and how these traits affect microbial dynamics, enzymatic activity, and nutrient release. Experimental findings from laboratory, mesocosm, and field studies are discussed to evaluate the performance of leaf litter amendments in PAH-contaminated soils. Additionally, the review considers synergistic combinations of leaf litter with other biostimulants, practical application strategies, seasonal availability, and potential limitations. This comprehensive synthesis highlights the multifunctional role of leaf litter in bioremediation and identifies future research directions for optimizing its use. By integrating ecological principles and microbial ecology, leaf litter-based bio-stimulation offers a promising, low-cost, and environmentally friendly approach for remediating PAH-contaminated soils.