Biodegradation of Aliphatic and Polycyclic Aromatic Hydrocarbons in Petroleum Oil-contaminated Soils.

Igunnugbemi, Olusoji Olusegun (2013) Biodegradation of Aliphatic and Polycyclic Aromatic Hydrocarbons in Petroleum Oil-contaminated Soils. PhD thesis, Lancaster University.

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Abstract

Crude petroleum and its refined products are principal energy sources driving industrialisation; albeit, the resultant pollution of the natural environment is antithetical to sustainable development. Soil pollution arising from the release of petroleum hydrocarbons causes changes in the soil microbial community structure and functional diversity, which can result in significant impact on soil ecosystem functioning. A number of physical, chemical and biological processes determine hydrocarbon fate in soil, but microbial degradation is generally considered to be the most important loss process. The overall aim of this project was to assess the biodegradation of aliphatic and polycyclic aromatic hydrocarbons in soils contaminated with petroleum oil. The effects of the presence and concentration of co-contaminants, the presence and concentration of HP-beta-CD, and of prescribed fire on microbial catabolic activity in soils were investigated. Selected soils from the UK and the Antarctic (SOM < 1-27% and clay < 0.01---42%) provided a good basis for evaluating the influence of soil physicochemical properties. Levels of hydrocarbons in the background soils reflect their proximity to anthropogenic input sources. Indigenous mineralisation of target hydrocarbons was measured using 14C-radiorespirometry in the background soils and soils amended with increasing diesel oil concentrations analogous to the spatial heterogeneity in contaminant levels common at polluted sites. The 14C-hydrocarbons used were naphthalene, phenanthrene, benzo[a]pyrene, hexadecane and octacosane. Collectively, the results from studies of effect of diesel concentration highlight the need to consider the potential variations in the development of indigenous catabolic activity towards various hydrocarbons when designing bespoke remediation strategies, as contaminant levels varied widely, even on a millimetre/centimetre-scale, in polluted soils. The efficiency of microbial utilisation of labile C-substrate was also influenced by the initial diesel concentration and soil contact time; the use of in-situ derived kEC values is advised to quantify microbial biomass-C in petroleum oil-polluted soils. The failure of HP-beta-CD to promote greater benzo[a]pyrene mineralisation despite a significantly enhanced solubilisation has weighty ecotoxicological implications for cyclodextrin-aided bioremediation of PAH-impacted soil. The negligible long-term effects on overall microbial activity and PAH degradative ability of soils and the substantial reduction of contaminant burdens in soil suggest low-severity prescribed fire as a practicable first-line option for remediation of heavily oil-polluted soils.