Effect of Biosurfactant and Biochar on Ecosystem Functions and Oil Remediation in Crude Oil Contaminated Wetland Soils

Abstract

Decontamination of oil spill from coastal wetland soils requires a delicate approach. Remediation strategies using biochar, biosurfactant, and nutrient additions have been proposed. However, there is little information on application of these with combination for treatment of crude oil-contaminated wetland soil. Therefore, incubation studies were carried out to investigate the impact of biochar and rhamnolipid (RL) biosurfactant along with nitrogen (N) application on petroleum hydrocarbon degradation in a Louisiana coastal saline marsh and their impacts on greenhouse gas (GHG) emission. Additionally, the toxicity of crude oil as well as remediation materials on coastal wetland ecosystem were assessed at three levels: saline marsh plant, algae and soil microbial community. Moreover, CO2production in coastal forest swamp and marshes under different levels of nitrate were studied. Rhamnolipids reduced the phytotoxicity induced by oil but inhibited algae growth, although this inhibition was reduced with addition of biochar. Also, both oil and RL elevated nutrient stress while biochar decreased their negative effects. Combined application of biochar and 0.1% RLhad low toxicity on marsh plant and soil microbes. Additionally, RL greatly increased the emission of carbon gas (CO2and CH4) while N increased N2O emission from the saline marsh soil. Biochar addition effectively reduced the increased N2O and CH4emission caused by N and RL.Application of RL + biochar + N effectively reduced total petroleum hydrocarbon (TPH) as well as both aromatic and aliphatic compounds, however, the remediation caused the reduction of soil bacterial diversity and a shift in the microbial community. Overall results demonstrate that the intergraded application of biosurfactant, biochar and N had a high efficiency on oil degradation in coastal saline marsh soil with low GHG emission andecotoxicity when used in oil remediation of contaminated coastal wetland soils.