Vermiculite of the Inagli Field as a Promising Material for Environmental Use at Reclamation Sites

This article discusses experimental studies of the use of local vermiculite from the Inagli field (Sakha Republic (Yakutia), Russia) as a recultivant on industrially disturbed permafrost-soil ecosystems of Yakutia after emergency oil spills. A brief description of the material composition, physical, chemical and technological properties of local vermiculite, which are close to the properties of vermiculite of the Kovdorskoe field (Murmansk oblast, Russia), is given. The sorption properties of Yakut vermiculite were tested on oil from the Talakan field, gasoline, diesel fuel, and toluene. Vermiculite of the Inagli field is a promising raw material for the production of oil sorbents, especially in connection with the increase in oil production, processing and transportation on the territory of Yakutia. The results of experimental application of hydrocarbon-oxidizing microorganisms (HOM) immobilized on vermiculite in oil-contaminated soils are presented. The technology of using vermiculite raw materials for oil pollution cleaning of various types of permafrost soils provides a significant environmental and economic effect, contributing to reducing the time of rehabilitation of disturbed lands and improving the environment of the disturbed territory.


Introduction
Despite intensive research on methods for restoring oil-contaminated soils, permafrost soils of Yakutia still remain poorly studiedin this regard. Self-recovery of disturbed lands takes place here over the years. Many modern researchers believe that the most effective and environmentally safe for northern ecosystems polluted by oil and petroleum products are biological cleaning methods based on the use of bacterial preparations [1][2][3][4][5][6][7]. However, the use of industrial biologics used to restore soil cover are ineffectivein cold climates. This is due to the fact that micro-organisms do not compete with the local soil microflora, or lose their activity while they are at the technological stage of manufacturing a biological product. Since only about 1-30% of dried microorganisms remain viable after lyophilization, and even those can lose their oil-oxidizing ability.
These circumstances demand scientific research on obtaining new forms of biosorbents based on local natural materials capable of active destruction of oil pollution at low temperatures.
The purpose of this research is to develop an effective technology for cleaning soils from oil pollution in the environmental and climatic conditions of Yakutia using biosorbents based on local natural raw materials.

Experimental part
This paper presents the results of a study of the effectiveness of a biological petroleum sorbent for cleaning permafrost soils from oil pollution. The sorbent is represented by a solid carrier substrate and a biodestructor of oil pollution immobilized on its surface.
Thermally expanded vermiculite from Inagli field (Yakutia) is used as the substrate carrier; as the biodestructor of oil -a strain of bacteria Pseudomonas panipatensis VKPM B-10593 at a concentration of 1×10 9 cells/cm 3 and cultured in a mineral medium with oil of the Talakan field, able to grow and degrade crude oil in soil at a wide range of temperatures (from +8 to +37 °C).

Characteristics of the strain
Pseudomonas panipatensis strain VKPM B-10593 was isolated from the water of lake Haly-Baly (Amginsky district, Central Yakutia), contaminated with Arctic diesel fuel. The strain was deposited in the all-Russian Collection of Industrial Microorganisms of FSUE Gosniigenetika (VKPM) (Moscow, 1st Dorozhny Ave., 1) under the registration number VKPM B-10593.

Physiological and biochemical features
The strain is aerobic. It grows at temperatures from + 8°C to + 41 °C. Optimum growth at +30...+37°C. It grows at pH 6.0-8.0 and in an environment with the addition of 0.1-2.0% NaCl. It has oxidase and catalase activity. As a source of carbon, it consumes acetate and citrate. Reduces nitrates. There is no denitrification activity. Does not hydrolyze gelatin. It has urease activity. Does not hydrolyze starch. Does not form lecithinase. Indole-negative. It oxidizes maltose and D-glucose. Does not ferment glycerin, Inositol, mannitol, rhamnose, sorbitol, raffinose, arabinose. Does not oxidize sucrose, mannitol, xylose, arabinose, fructose, galactose. Does not need additional growth factors.

Characteristics of the carrier substrate
According to many authors, natural mineral materials are preferred for immobilization of HOM. In this case, the carrier sorbent used for cell immobilization must have the following main properties: permeability, oil capacity, non-slumping ability, porosity and flowability. Expanded vermiculite meets these requirements to the fullest extent possible (GOST 12865-67).
Vermiculite is a secondary mineral, resulting from the hydration of phlogopite and biotite and is related to complex ferrous-magnesium silicates of the group of hydromicas. Its chemical composition is variable and can be approximated by the formula (Mg 2+ , Fe 2+ , Fe 3+ ) 3 [(Si, Al) 4 O 10 ]·(ОН) 2 ·4Н 2 О. Color bronze-yellow to brown, greenish. Leaves are soft and flexible. The structure is close to montmorillonite, the cleavage is perfect. Hardness 1-1.5; density 2.3 g / cm 3 ; melting point about 1400 °C. [14,15,16].
Vermiculite has the ability to swell when heated and significantly (10-25 times) increase in volume with the formation of a loose granular material of a scaly structure, which, due to its low bulk mass, low thermal conductivity, high sound insulation properties, chemical inertia and fire resistance, is used in construction, agriculture, environmental protection, etc. [16,17,19,20].
However, due to the lack of special equipment, the production of vermiculite and materials based on it in Russia is only beginning to develop and is still limited [20].
Vermiculite from the Inagli field (Yakutia), located 30 km to the west from the city of Aldan in the upper reaches of the Inagli stream, was used as an adsorbent and carrier for the immobilization of HOM. Inagli is the right tributary of the Aldan river, confined to the eponymous array of ultrabasic alkaline rocks. The deposit is associated with the weathering crust of chromdiopside-mica metasomatites formed from the dunites of the Inagli pluton. The field has estimated reserves of vermiculite of categories C 1 + C 2 in the amount of 618 thousand tons. The prognostic reserves of vermiculite in the Inagli massif (taking into account the explored ones) can be estimated at 1 million tons [14,21].
The Thus, expanded vermiculite is a promising carrier sorbent used for the immobilization of HOM cells, since it has the main properties listed above, namely: permeability, oil capacity, non-slumping ability, porosity and flowability; it combines the properties of a carrier for microorganisms and a sorbent for oil, which provides high efficiency and prolongation of reactions of destruction of petroleum hydrocarbons.

Results and discussion
Based on the above research results, a biosorbent was developed for cleaning soils from oil pollution [10, [22][23][24].
Field experiments with the use of the preparation were conducted on permafrost heavy loam soil contaminated with oil.
The initial content of petroleum products in the soil of the experimental site before applying the biosorbent was 44319 mg/kg.
The efficiency of cleaning was assessed by the degree of degradation of oil pollution, by the dynamic pattern of the number of major groups of soil microorganisms and by soil phytotoxicity.
The oil content in the soil was determined by gravimetric method according to the instruction RD52. 18.647-2003. It was found that the degree of biodegradation of petroleum products in the experimental site for 1 growing period after the introduction of biosorbent into the soil was 76.7 % (Table 2). The dynamics of biodegradation of oil pollution was consistent with the dynamics of accumulation of soil microorganisms, including oil destructors, whose number increased by an average of 2 orders of magnitude after the introduction of biosorbent into the soil. Microorganisms were recorded in the colony forming units (CFU) per 1 gram of absolutely dry weight (ADW) of the soil (Table 3). Biotesting showed that phytotoxicity decreased in the process of clearing oil contamination in the soil of the experimental site, as evidenced by an increase in the percentage of germination of test plant seeds from 30 to 68%.

Conclusion
The obtained results indicate the effectiveness of the biosorbent for cleaning permafrost soils from oil pollution.
The advantage of the biosorbent is that due to the combination of unique properties of the carrier substrate (expanded vermiculite) and the strain of bacteria Pseudomonas panipatensis VKPM B-10593 immobilized on it, which is able to develop and destroy oil and petroleum products in a wide temperature range (from +8 °C to +37 °C), it has the ability to stimulate the biological degradation of petroleum products in the soil.
The method of preparation and use of biosorbent is cost-effective, since it does not require complex technological equipment for its implementation. And vermiculite, which serves as a carrier substrate in this biosorbent, is both an affordable and cheap raw material, since vermiculites have a surface occurrence and are developed in an open-cut way.
Cleaning the soil from oil contamination with the obtained biosorbent allows to prevent the spread of pollutants to the adjacent landscapes and to eliminate the spots of contaminated soil, which significantly improves the sanitary and environmental condition of the disturbed territory.