ISSN 10642293, Eurasian Soil Science, 2015, Vol. 48, No. 3, pp. 314–324. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © I.I. Tolpeshta, S.Ya. Trofimov, M.I. Erkenova, T.A. Sokolova, A.L. Stepanov, L.V. Lysak, A.M. Lobanenkov, 2015, published in Pochvovedenie, 2015,
No. 3, pp. 360–372. 314
Redox processes in native and oilcontaminated waterlogged soils. A large area of oilcontaminated lands in the Russian Federation is occupied by peat soils of the northern and middle taiga highmoors.
The hydromorphic soils are characterized by low redox potentials, which significantly complicate the biological remediation of oilcontaminated soils using industrial preparations containing aerobic microor ganisms. It was shown that the value of the Eh in the highmoor peat soils decreases with depth, and the size of the zone with reductive conditions depends on the depth of the bog water . The study of 694 peat soil samples from Poland and Holland showed that the value of the Eh varied under complete flooding in the range from –100 to 100 mV . Fahmi et al. showed that the Eh value in the surface layer of peats under complete flooding can decrease to 0 mV . It was found that the value of the Eh in the 0.75cm thick layer of undisturbed high (oligotrophic) moors varies in the range from +858 to –140 mV . The low redox potential of the waterlogged soils is due to the presence of reductants . The reduction reactions occur successively with the direct participation of microorganisms. In the course of anaerobic respira tion, organic matter is oxidized, and more and more reductive conditions are developed in the soil. In the waterlogged soils, organic matter and inorganic com pounds such as Fe2+, Mn2+, S2–, CH4, and H2 act as electron donors. The role of electron acceptors in the soil belongs to inorganic compounds such as O2 under oxidative conditions and MnO2, FeOOH, and CO2 under reductive conditions .
The aerobic oxidation of organic matter and the anaerobic degradation of organic compounds during denitrification, the reduction of Mn and Fe, and meth anogenesis with the participation of microorganisms with different types of metabolism occur in different Eh ranges [33, 53]. Under oxidative conditions at pH of about 7 and in the Eh range above +300 mV, aerobic microorganisms participate in these reactions. Under moderately reductive anaerobic conditions at Eh values of +100 to +300 mV, facultative anaerobes reduce nitrogen and manganese. The reductive anaerobic con ditions in the Eh range from –100 to +100 mV are favorable for the respiration of facultative anaerobes reducing Fe3+ and partly S6+. The strict anaerobes uti lize sulfates for respiration under reductive conditions at Eh of –200 to –100 mV and CO2 under strongly reductive conditions at Eh of –300 to ⎯200 mV .
Nitrates, sulfates, iron and manganese com pounds, and an organic substrate are always present in the waterlogged soils, where an oxygen deficiency 4, +NH 3, −NO 2 4 , −SO
AND CONSERVATION OF SOILS
Laboratory Simulation of the Successive Aerobic and Anaerobic
Degradation of Oil Products in OilContaminated HighMoor Peat
I. I. Tolpeshta, S. Ya. Trofimov, M. I. Erkenova, T. A. Sokolova, A. L. Stepanov,
L. V. Lysak, and A. M. Lobanenkov
Faculty of Soil Science, Moscow State University, Moscow, 119991 Russia email: firstname.lastname@example.org
Received May 21, 2014
Abstract—A model experiment has been performed on the successive aerobic and anaerobic degradation of oil products in samples of oilcontaminated peat sampled from a pine–subshrub–sphagnum bog near the
Sutormin oilfield pipeline in the YamalNenets autonomous district. During the incubation of oilcontami nated peat with lime and mineral fertilizers under complete flooding, favorable conditions are created for the aerobic oxidation of oil products at the beginning of the experiment and, as the redox potential decreases, for the anaerobic degradation of oil products conjugated with the reduction of N5+ and S+6 and methanogenesis.
From the experimental data on the dynamics of the pH; Eh; and the , , and concentrations in the liquid phase of the samples, it has been found that denitrifiers significantly contributed to the biodeg radation of oil products under the experimental conditions. After the end of the experiment, the content of oil products in the contaminated samples decreased by 21–26%.
Keywords: oil pollution, aerobic–anaerobic degradation of oil products, denitrification, sulfate reduction, methanogenesis, oil products, highmoor peat soils
DOI: 10.1134/S1064229315030126 −NO3 2 −NO 24 −SO
EURASIAN SOIL SCIENCE Vol. 48 No. 3 2015
LABORATORY SIMULATION OF THE SUCCESSIVE AEROBIC 315 occurs sometimes. The oligotrophic peat is depleted in iron and manganese [8, 19].
It was shown that the degradation rate of organic matter in the samples of peat and mineral soils under aerobic respiration is higher by three times on the average than at the denitrification, sulfate reduction, and methanogenesis .
Optimal conditions for nitrification are created in the soil at Eh of 400–500 mV and pH close to 7.5–8.0.
Nitrifiers are most active in the temperature range from 25 to 30°C [24, 35]. In distinction from the eutrophic nitrifiers, the heterotrophic nitrifiers can oxidize nitrogen of different organic compounds .
Denitrification in soils is carried out by bacteria, algae, fungi, and yeasts. The complete denitrification to molecular nitrogen is fulfilled only by prokaryotes, most of which are facultative chemoorganotrophic anaerobes of many genera utilizing nitrates as oxidants of organic substrates. They include, e.g., some bacte ria of the Alcaligenes, Bacillus, Paracoccus, Pseudomo nas, Thiobacillus, and other genera . The activity of denitrification depends on the content of oxygen, the temperature, the soil moisture, and the pH . It was found that the denitrification rate positively correlates with the pH and reaches an optimum at pH values of 7.0–8.0 . According to different authors, the opti mum temperature range for denitrification in soils is 25–32°C .