Surfactant-enhanced treatment of oil-contaminated Arctic tundra soil: Ecotoxicological assessment

During 2018-2019 summer expeditions to the Yamal peninsula, we collected tundra gley soil samples at the oil-contaminated sites. The contamination level was determined by fluorimetry and was ranged from 30 to 107 g/kg. The soil quality was evaluated by its enzymatic activity; the low catalase activity of the soils confirmed the presumed slow soil natural attenuation and the need for land remediation. The oil-contained and background samples were ex-situ treated with the aqueous solutions of non-ionic BOK6 and anionic AddiMax PV01 synthetic surfactants. The treatment efficiency reached 71 +/- 2% and 97 +/- 3% in the experimental design with BOK-6 and AddiMax PV01, respectively. We derived the ecotoxicity endpoints for the surfactant solutions, using infusoria Paramecium caudatum Ehrenberg and higher plants Raphanus sativus L. and Avena sativa L. The protozoan mortality was studied and resulted in LC50-24 values << 0.1 mg/L and 339 mg/L for BOK-6 and AddiMax PV01, respectively. Both surfactant solutions and surfactant residues in soil showed the inhibition potential towards higher plants. BOK-6, with a strong relation to its chemical and ecotoxic profile, completely inhibited seed germination in the treated soil. The less ecotoxic surfactant AddiMax PV01 inhibited plant growth by 38% compared to control. The treatment increased ecotoxicity and dehydrogenase activity and further lowered the catalase activity of the background soil, and, therefore, the surfactant residues migrating to the non-contaminated territories should be controlled. By this study, we show the efficiency of the surfactant-enhanced remediation of arctic soils, but the associated environmental risks must be addressed. (C) 2021 Elsevier B.V. All rights reserved.