Combined application of biochar, compost, and bacterial consortia with Italian ryegrass enhanced phytoremediation of petroleum hydrocarbon contaminated soil

Abstract

Petroleum hydrocarbons are extensively utilized in petrochemical industries and cause soil deterioration during exploration, transportation, refining and making petroleum products. We hypothesized that the combined use of compost, biochar and bacterial consortia as soil amendments may enhance the rhizoremediation potential of ryegrass by strengthening the plant rhizospheric effect for efficient total petroleum hydrocarbon removal. The present study focused on phytoremediation of hydrocarbons in spiked contaminated soil amended with biochar (5% v/v), and compost (5% v/v). Spiked soil was inoculated with consortia of four hydrocarbon degrading bacterial strains (Pseudomonas poae, Actinobacter bouvetii, Stenotrophomonas rhizophila and Pseudomonas rhizosphaerae). The spiked soil was prepared by spiking agricultural soil with 3.4% (w/w) of crude oil. Italian ryegrass (60 seeds pot−1) were sown and plants were harvested after 75 days.The highest hydrocarbon removal (85%) was observed in spiked soil amended with compost, biochar and consortia. Bacterial inoculation with biochar and compost showed significantly higher hydrocarbon degradation as compared to all other treatments. Highest TPHs degrading bacteria (5.74 × 107 cells g−1 of soil) were observed in rhizosphere of spiked soil amended with compost, biochar and consortia. The organic amendments improved plant growth and bacterial count in rhizosphere which resulted in higher removal of hydrocarbons. We concluded that plant-microbe interactions together with the organic soil amendments offer an emerging trend for remediation of hydrocarbons. Rhizoremediation is a green solution to overcome the quandary of total petroleum hydrocarbon contamination in soil.