Justification of normative standards concerning residual oil content in industrial soils in the Republic of Tatarstan after recultivation and soil remediation operations

Abstract

© 2019, Neftyanoe Khozyaistvo. All rights reserved. The paper presents justification for normative standards concerning permissible residual oil content and products of its transformation in industrial soils after recultivation and soil remediation operations. The test objects were samples of soils with background matter content and recultivated soils of nine types collected on the territories of Tatneft PJSC E&P activities, as well as model samples contaminated with the most toxic sulfur crude oil produced from the Carboniferous reservoirs. The model samples met the requirements concerning the content of dissolved solids of aqueous extracts of soils, chlorides, sulfates, and heavy metals. The experimental justification of normative standards was based on four basic nuisance values: migratory aqueous, migratory air, translocation, and general sanitary nuisance values, in compliance with the principles of regulation of industrial lands’ soils. General sanitary tests using oil-contaminated model soil samples included determination of population of main groups of soil micro-organisms: heterotrophs, hydrocarbon-oxidizing, spore-forming actinomycetes, micromycetes, nitrogen fixers, I phase nitrifiers; fermentation activity of soil microflora (urease and catalase); parameters of soil respiration (basal respiration, substrate-induced respiration, content of carbon in bacterial biomass, coefficient of bacterial respiration); biotesting of aqueous extracts of model soils using monocotyledon seeds (spring wheat, Triticum vulgare L.); biotesting of aqueous extracts of model soils to determine presence of Ceriodaphnia affinis and Paramecium caudatum; determination of acute toxicity using monocotyledon seeds (Triticum vulgare L.) and chronic phytotoxicity using higher monocotyledon (Triticum vulgare L.) and dicotyledon (field pea, Pisum sativum L.) plants. As a target normative standard, the least content of oil products was selected out of the experimental data on the four nuisance values. When establishing normative standards concerning permissible residual concentration of oil products in soils, it was found that the migratory aqueous and the migratory air nuisance values are not limiting in the tested range of concentrations, while the general sanitary nuisance value is limiting. Based on the results of the surveys considering the limiting content of oil products in the model soil samples and taking into account the assumed error (25 %) for the methods to determine the mass fraction of oil products in soil for the purpose of the state ecological monitoring, we recommend the following normative standards concerning permissible concentration of oil products for Tatarstan soils: 10 g/kg for soddy-calcimorphic leached, light-gray forest soil; 11 g/kg for soddy-calcimorphic podzolized, sod-podzol, gray forest soil, dark-gray forest soil; 12 g/kg for typical black humus earth (chernozem), leached and podzolized.