Abstract
Bioremediation offers an attractive and environmentally friendly solution for clearing soil hydrocarbon contamination. The efficiency and completion of remediation must be assessed using environmental risk assessment criteria. As a result, toxicological indicators have become essential for evaluating the recovery of contaminated soils to support traditional chemical analyses. In this study, the relationship between hydrocarbons (kerosene and diesel) and toxicological indicators was evaluated in three amended soil types (Fresh Boyndie, Insch and Brechin) collected from different areas in Aberdeenshire (UK). Toxicological response assays of higher organisms were performed with two species of earthworms (Eisenia fetidaandLumbricus terrestris) and two plant species (wheat (Triticum aestivum L.) and white mustard (Brassica albaL.)). The plant assays included the evaluation of seed germination, root elongation, the germination index (GI) and plant shoot height. All assays were performed sequentially in kerosene and diesel-amended soils under both incubated and non-incubated treatments. The results showed that soil type played a fundamental role in the response observed in the assays, and some assays therefore showed sensitivity across all three soils. Seed germination was an insensitive indicator in both mustard and wheat plants. Root elongation and the germination index (GI) in mustard were more sensitive than those in wheat assays in all three soils. Additionally, wheat shoot height was more sensitive than mustard shoot height in distinguishing between the soil treatments. The two earthworm species used in the study showed similar responses to each other, and both species were highly sensitive to hydrocarbons. However, the assays were unable to differentiate between the incubated hydrocarbon-amended treatments and the equivalent controls. This study confirmed that toxicity assays should be used in addition to hydrocarbon analysis in such studies when soil recovery is assessed.