The study of the integral toxicity of oil-contaminated soil

Abstract

The effect of contamination with technical waste oil on the integral toxicity of sod-podzolic sandy loam soil under field experiment conditions was studied. The integral toxicity of the soil aqueous extract was determined using the «Ecolum» bacterial test, which is a luminescent gene-engineered Escherichia coli. Control soil samples show acceptable levels of toxicity. Soils contaminated with 10 or 20 g/kg doses of petroleum products are moderately toxic. The dose of 30 g/kg makes the soil highly toxic for luminescent microorganisms. The hydrocarbon composition of technical waste oil was determined using spectral coefficients obtained by infrared spectrometry. High content – 6.73% – of aromatic hydrocarbons (the most toxic fraction) was revealed. Correlation analysis between the soil toxicity index, the content of oil products, heavy metals (Co, Ni, Cu, Zn, Pb) and the pH of the soil aqueous extract showed a very strong positive correlation between toxicity and zinc content (r = 0.88) and oil products content (r = 0.83) in the soil, as well as a high negative correlation on soil pH (r = –0.61). The phytomass of plants growing on contaminated sites was determined. A very high inverse correlation (r = –0.82) between the content of oil hydrocarbons in the soil and phytomass confirms that soil contamination with an increased dose of oil products reduces the biomass of the aboveground part of plants. A general tendency to displacement of monocots and their replacement by dicots was observed for polluted soils.