Laboratory studies on the effects of oil pollution on soil properties

Soil pollution is one of the world’s most debated and widespread environmental issues. In particular, oil spills pose a significant global threat, with an environmental impact only slightly below that of radioactive contamination. This study conducted laboratory tests on the granulometric composition and consistency limits of soil samples artificially contaminated with engine oils. Three different types of engine oils were added to the soils in proportions of: 2.5%, 5% and 10% by dry weight of the soil sample, respectively. The trends in changes of the parameters determined due to pollution were evaluated. The study included a comparative analysis of the results of studies on the parameters of polluted soils carried out in Polish and foreign scientific centres. For silty sand (siSa), the content of the clay fraction decreased from an initial 7% to a range of 1–3%. For clayey sand (clSa), the content of the clay fraction decreased from 13% to a range of 1–7%. The plastic limit (PL) was 13.24% for siSa and 16.42% for clSa. The tested soils contaminated with engine oil were classified as non-plastic. The liquid limit (LL) for siSa and clSa was around 21%. The LL of siSa decreased from 21% to 15% due to contact with all types of engine oils. For clSa, the LL decreased to a range of 10–14%, depending on the type of engine oil. The results of this study highlight the engineering importance of understanding soil behaviour under oil contamination, which is crucial for assessing the stability and safety of structures in contaminated areas and for designing effective remediation strategies.