Screening Plants for Electrokinetic Petroleum Remediation: Tall Fescue Outperforms by Mitigating Soil Electrochemical Deterioration

Electrokinetic (EK) remediation improves contaminant transport in low-permeability soils, but persistent electric fields degrade the soil electrochemical habitat, reducing treatment efficiency. Combining EK with plants may mitigate this deterioration, yet plant selection criteria remain unclear. This study screened tall fescue (Festuca arundinacea), ryegrass (Lolium perenne), corn grass (Zea mexicana (Schrad.) Kuntze), and alfalfa (Medicago sativa) in 60-day EK-assisted remediation of petroleum-contaminated silty clay under periodically reversed polarity. Petroleum removal, current dynamics, and soil physicochemical and biological indicators were monitored. Tall fescue performed best, achieving the highest petroleum removal (20.21%), greatest electrical conductivity, dissolved organic carbon, and field water-holding capacity, and the largest microbial abundance and dehydrogenase activity. Ryegrass performed similarly. Corn grass showed the tallest shoots but ranked third; alfalfa was least effective. Enhancement beyond simple additivity was species-dependent, observed only for tall fescue and ryegrass. Root-length stimulation correlated with remediation performance, while shoot-height response did not. Plants that mitigated electrochemical deterioration and sustained rhizosphere microbial activity were most suitable. Tall fescue is recommended, with ryegrass as a strong competitor. This study provides a transparent multi-indicator screening framework for selecting plants in EK-phytoremediation systems.