Physicochemical and Ecotoxicological Characterization of Petroleum Hydrocarbons and Trace Elements Contaminated Soil

Abstract

Underground storage tanks used for auto oil spill waste contain many hazardous materials, including polycyclic aromatic hydrocarbons (PAHs) trace elements. These compounds pose a significant threat to the environment and affect negatively human health. The aim of this study was to characterize the soil of a former auto scrap yards in which oil spill tank leakage occurred in Sweden. The soil samples were collected from an area of 5 m2 around an oil the tank which was highly contaminated with petroleum hydrocarbons (PHC) and trace elements (cobalt and lead). Another soil samples were collected from a nearby area that was not contaminated by PHC and they were considered as controls. The characterization of these soil samples was performed using two approaches. Analysis of the relevant physico-chemical soil properties included texture, organic matter, contaminant concentration and pH, while biological analyses were performed using three independent ecotoxicological tests with plant (Lepidium sativum), earthworm (Eisenia fetida) and soil microorganisms. Toxicity tests showed that contaminants had strongly negative effects on earthworm’s development and L. sativum shoots dry biomass in both PHC contaminated and control soils. These two parameters were the most sensitive in reflecting toxicity of study soils. Oxygen uptake rate (OUR) in aqueous phase was four times higher than that of the solid phase even though a similar trend was observed in both phases (aqueous and solid). Moreover, microorganism’s respiration was high in PHC contaminated soils in comparison to control soils due to the mineralization of readily available OM and/or organic pollutants as well as the inhibitory effect of TE on soil respiration. The results clearly demonstrated that combination of chemical analyses with three toxicity tests was appropriate to characterize mixed PHC and TE contaminated soils.