ИСТИНА

149 Evaluation challenge of waste toxicity at oil extraction E. Kovaleva, Soil Science Faculty, Moscow State University / Soil Science Faculty; M. Guchok, ANO Ecoterra; S. Ledovskikh, Ecoterra Autonomous Non-Commercial Organization; P. Korolev, Moscow State University / Department of Soil Science; V. Terekhova, Lomonosov Moscow State University / Lab of Ecotoxicological Soil Analysis. Increasing oil extraction activity all over the world, imperfect technologies of oil production leads to formation of different wastes, containing petroleum hydrocarbons. Drilling cuttings are one of the oil extraction wastes, consisting of solid rock material and residuals of drilling fluid. Drilling cuttings could be landfill or utilize to recultivants. Being contact with environmental components, drilling cuttings or their composites, could impact the environment and remain toxic effect for many years. Ecotoxicological tests in combination with chemical studies could be the most suitable approach to assess the ecotoxicity of oily wastes and prevent contamination risk. We studied the ecotoxicity of drilling cuttings and the composites, formed on the base of drilling cuttings, in order to find the safety admixture and their ratio to return a waste in transformed state into environment. Five different admixtures and the wastes were tested. Drilling cuttings were mixed with sand to improve physical characteristics, peat and kieselguhr (diatomaceous earth) to increase the sorption capacity, phosphogypsum to regulate the acid medium of the mixture and cement to give mechanical robustness. We applied the bioassay to assess the toxicity of drilling cuttings and the formed composites. We evaluated the initial concentration of contaminants in aqueous extracts from wastes and compositions that may immobilize 50% of crustaceans and infusorians, but available approaches of bioassay have significant restrictions for implementation. The tested samples contained high level of water soluble salts (up to 50 g kg-1).The eluate and direct phytotoxicity tests were run, using seeds of mustard (Sinapis alba L.) and oat (Avena sativa L.). The drilling cutting samples with TPH content higher than 3.0 g kg-1 were toxic, then how the composite variants with TPH content less than 35 g kg-1 stimulated the plant growth compared with the control. Treatment with kieselguhr and peat allowed sorbing TPH and tracing metals, that approved a positive effect of chosen ingredients and their ratio. The water filtrates characterized by neutral pH (7.4), TPH content between 1.5-3.1 mg L-1 . We conclude it is the shortage of appropriate approaches for ecotoxicity assessment of wastes and obtain the solid results. It is highly demanded to work out new methods to evaluate the toxicity of specific waste based on their composition, properties, aggregation and natural conditions of zone they formed.