Enhanced Phytoremediation of Petroleum Sludge‐Contaminated Soil by Saltmarsh Plants ( Salicornia sinus‐persica ); Assessment of the Amendment Effects of Biochar and Vermicompost

Petroleum sludge poses significant environmental challenges due to its complex composition of hydrocarbons and heavy metals. Due to the high costs and limitations of physical and chemical remediation methods, bioremediation is recognized as a cost‐effective and efficient approach for decontaminating hydrocarbon‐polluted soils. This study investigates the enhanced phytoremediation of petroleum sludge‐contaminated soil using the halophyte Salicornia sinus‐persica and assesses the synergistic effects of biochar and vermicompost as soil amendments. A 6‐month greenhouse experiment was conducted using soil contaminated with petroleum sludge concentrations ranging from 0% to 8% (w/w). Treatments included unamended soil, biochar amendment, vermicompost amendment, and a combined biochar‐vermicompost amendment, with setups for planted, unplanted, and sterile unplanted conditions. Results demonstrated that petroleum sludge concentrations above 4% significantly inhibited seed germination, but amendments mitigated these effects. The presence of S. sinus‐persica combined with amendments significantly enhanced total petroleum hydrocarbon (TPHs) removal in the soil. The highest TPH removal efficiency (54.1%) was achieved in the 0.2% sludge treatment with combined amendments and plants. However, at higher contamination levels (4%–8% sludge), removal efficiencies were considerably lower (ranging from 19% to 37%), and plant growth was severely inhibited at 8% sludge. These results indicate that S. sinus‐persica with biochar and vermicompost amendments is effective for low to moderate petroleum sludge contamination but has limited applicability at high contamination levels without additional pretreatment or dilution.