The potential for biotransformation of weathered hydrocarbon residues in soils collected from two commercial oil refinery sites (Soil A and B) was studied in microcosm experiments. Soil A has previously been subjected to on-site bioremediation and it was believed that no further degradation was possible while soil B has not been subjected to any treatment. A number of amendment strategies including bioaugmentation with hydrocarbon degrader, biostimulation with nutrients and soil grinding, were applied to the microcosms as putative biodegradation improvement strategies. The hydrocarbon concentrations in each amendment group were monitored throughout 112 days incubation. Microcosms treated with biostimulation (BS) and biostimulation/bioaugmentation (BS + BA) showed the most significant reductions in the aliphatic and aromatic hydrocarbon fractions. However, soil grinding was shown to reduce the effectiveness of a nutrient treatment on the extent of biotransformation by up to 25% and 20% for the aliphatic and aromatic hydrocarbon fractions, respectively. This is likely due to the disruption to the indigenous microbial community in the soil caused by grinding. Further, ecotoxicological responses (mustard seed germination and Microtox assays) showed that a reduction of total petroleum hydrocarbon (TPH) concentration in soil was not directly correlable to reduction in toxicity; thus monitoring TPH alone is not sufficient for assessing the environmental risk of a contaminated site after remediation.
This work was supported by the LINK Bioremediation programme (BIOREM_35), the Environment Agency and the Biotechnology and Biological Sciences Research Council BBSRC (Grant BB/B512432/1). The authors also thank the UK Engineering and Physical Sciences Research Council (EPSRC) for financial support to carry out this work through a CASE award supported by the former FIRSTFARADAY (Environmental Sustainability KTN) partnership (Ref No. 5010978). The views expressed are authors’ alone and may not reflect the views or policies of their employing organisations.
- soil contamination
- weathered petroleum hydrocarbon
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- Biological Sciences, Aberdeen Centre For Environmental Sustainability - Head of School of Biological Sciences, Chair in Biological Sciences
- Engineering, National Decommissioning Centre
- Centre for Energy Transition
- Marine Alliance for Science and Technology for Scotland (MASTS)