Zubaidullin A.A.

As is known, most of the oil-contaminated lands available in the Nizhnevartovsk region are sphagnum raised bogs with a thick layer of peat deposits. And it is on these lands that the use of traditional reclamation technologies and conventional technical means, as modern practice shows, not only does not bring positive results, but in some cases even helps to slow down the natural processes of self-healing that have begun.

First of all, this is due to underestimation natural features of the indicated biotopes: their high water content, low-bearing capacity of the surface and, most importantly, the uniqueness of the soil and plant complex, which together create significant difficulties for the application of standard schemes for the reclamation of oil-contaminated lands.

Let us clarify that the word “reclamation” here means the entire range of work carried out in the disturbed area and includes: collection and neutralization of petroleum organic matter, restoration of soil fertility and creation of stable vegetation cover. The next most common reason for negative results in the remediation of all oil-contaminated areas without exception, including those located in raised bogs, is ignorance (out of ignorance, for mercantile and other reasons) of the stages of action of natural mechanisms of oil decomposition on the earth's surface. For our region, there are three main stages of natural destruction of oil on the earth’s surface (Figure 1):

Stage I - lasts on average 1.5 years. Physicochemical processes prevail here, including the penetration of oil deep into the soil, evaporation of light fractions, leaching, oxidation by atmospheric oxygen and photochemical decomposition of petroleum hydrocarbons. The concentration of oil in the soil during this period decreases by 40-50%.

Stage II - lasts 3-4 years after the end of the first. Here, oil decomposition occurs under the influence of soil hydrocarbon-oxidizing microorganisms, the number of which increases by 25 times. Methane-naphthenic fractions, which are the most toxic components of oil for plants and soil animals, are destroyed.

Stage III - begins 4.5-5 years after the oil spill and lasts until it is completely destroyed. The stage is characterized by microbiological decomposition of the remaining less toxic part of hydrocarbons and resinous-asphaltene components, which form continuous hard crusts on the contaminated surface - the so-called kirs. In fact, already at the very beginning of the stage, it is possible to restore some plant species that are resistant to increased oil content in the soil. But their appearance is prevented by kirs, which do not allow air to penetrate into the root layer of peat, causing a kind of suffocation of plants and soil animals. From a chemical point of view, the process of natural oil destruction ends completely in no less than 25 years, however, the toxic properties of oil disappear after 10-12 years, the products of its decomposition are partially included in the soil humus, partially dissolved and removed from the soil profile.

Own research conducted in summer season 1996 on the territory of the Vatinskoye oil field (JSC Slavneft-Megionneftegaz), confirmed the presence of stages of natural degradation of oil in contaminated areas of raised bogs. Observations were carried out in three similar areas, representing the biocenosis of a ridge-hollow raised bog, which were subject to oil pollution at different times: a relatively recent spill in 1994, an old one in 1989. and old - 1985 The timing of the accidents was selected taking into account the already indicated stages of physicochemical and microbiological destruction of petroleum hydrocarbons and the associated stages of self-healing of disturbed phytocenoses. However, the duration of each of them, as shown by a field survey, in the conditions of high peat bogs exceeds those given (for drained areas) by 1.5 - 2 times, which is due to the specifics of peat bog soils (low intrasoil temperatures, lack of oxygen and minerals).

Only taking into account all of the above can we correctly structure the course of the reclamation process, optimally engaging and using all existing natural self-purification mechanisms, and obtain a significant environmental and economic effect, if this term is appropriate in this case. This effect is achieved due to two indicators:

Significant reduction in the period of cleansing and restoration of disturbed areas to their original conditions;

Reducing the overall material costs for reclamation.

Now directly about the most typical mistakes allowed when carrying out reclamation work in oil-contaminated areas of swamps. Quite often you can see how the following measures are used in the first two years when cleaning up fresh oil spills:

1) backfilling of contaminated areas with sand and peat,

2) plowing or loosening the surface with agricultural implements (harrows, plows, etc.) and all-terrain vehicle tracks,

3) introduction of oil-oxidizing microorganisms.

Unfortunately, each of these activities is actually a waste of effort and money from an environmental point of view. Moreover, in most cases, nature is rendered a kind of “disservice”, as a result of which much more damage is caused to swamp ecosystems than directly from the oil spill itself.

Thus, the implementation of the first two measures leads only to a temporary beautification of the ugly landscape and the achievement of acceptable oil concentrations in the “upper” (imported or inverted underlying) layer of soil in accordance with the requirements of the environmental inspection. In fact, oil is buried and preserved in the underlying water-logged layers of peat, where low temperatures and lack of free oxygen. For example, when heavy tracked swamp vehicles such as GPL, Vityaz, etc. move across the oil-contaminated surface of a swamp, oil is squeezed out and buried in a peat deposit at a depth of up to 50 cm. And with the natural distribution of oil over the surface, an average of 5-10 centimeter layer of peat deposit. All this removes residual oil from the action of natural physicochemical decomposition mechanisms (atmospheric oxygen and sunlight) for several years, and therefore the overall restoration of stable soil and vegetation cover significantly slows down. At the same time, the existing vegetation cover is also completely destroyed (covered or torn off by caterpillars), which could survive on individual elevations and hummocks and be a source of vegetation spread on contaminated lands in subsequent years.

The use of oil-oxidizing microorganisms (bacteria) is also inappropriate at this stage, since most of them die due to the acute toxicity of freshly spilled oil. In addition, the processes of biodegradation primarily involve lighter fractions of oil (a kind of “cream”), which would otherwise quickly collapse under the influence of atmospheric oxygen and sunlight.

Thus, it is advisable to accelerate the natural processes of destruction of residual oil and thereby reduce the time required to restore the original vegetation cover only after one and a half to two years from the moment of the accident (at stages II and III).

However, this does not mean that fresh spills should not be dealt with. It’s just that all efforts must be directed towards reliable localization of the oil spill within the smallest possible area and collection of the maximum possible amount of oil. Modern technical means make it possible to collect up to 70%, and under favorable natural conditions, up to 90% of spilled oil.

In swamps, localization of spills is carried out, as a rule, either by creating a thick peat embankment along the perimeter of the spill (swamp vehicles of the "KART" type are used), or by tearing off guide trenches and furrows to a common receiving pit, or by installing mobile booms (the latter, unfortunately, is not practiced). Oil is collected using conventional pumping equipment and specialized oil skimmers. Effective in swamps and used for collecting oil from inter-tussock depressions and other hard to reach places backpack vacuum pumps, both domestic and imported. The main condition should be minimal movement of equipment and people on the reclaimed surface, especially on preserved areas of living vegetation.

The most acceptable method for thoroughly collecting residual oil, according to our own experience in carrying out such work, is the method of forced washing of soil and vegetation from oil with water. This is achieved either by completely flooding the contaminated area for a short period, or by periodically sprinkling it with irrigation systems (motor pumps, forest fire engines). The effectiveness of oil cleanup work at a site is significantly increased by the use of permitted surfactants.

For small volumes of spilled oil, an effective measure is the use of sorbents, in particular peat mats (the holding capacity of 1 m2, depending on the manufacturing technology, ranges from 10 to 40 kg of oil with 12-15 times of use). Such mats are convenient for quick deployment on fresh spills and, most importantly, convenient for their subsequent collection for disposal, unlike loose types of sorbents. By the way, there are simple domestic technologies for mass production of such mats locally. The natural mineral vermiculite, which has significant reserves in our mountain Trans-Urals, also has unique sorption properties.

PAGE \* MERGEFORMAT 12

MINISTRY OF AGRICULTURE OF THE RUSSIAN FEDERATION

Department of Real Estate Cadastre and Geod e zia

OPD.V.04 LAND RECLAMATION

METHODOLOGICAL INSTRUCTIONS

for practical lesson No. 4 on the topic:

“Reclamation of lands contaminated with oil and petroleum products”

Specialty 120301 Land management

Ufa 2012

UDC 631.4

BBK 40.3

M 54

Considered and discussed at a meeting of the Department of Real Estate Cadastre and Geodesy (protocol No. from 2012)

Compiled by: Associate Professor, Candidate of Agricultural Sciences Minniakhmetov I.S.

Reviewer: Candidate of Agricultural Sciences, Associate Professor of the Department of Agriculture and Soil Science

Gay sin V.F.

Responsible for release: head. Department of Real Estate Cadastre and Geodesy, Candidate of Agricultural Sciences, Associate Professor Ishbulatov M.G.

Ufa, BSAU, Department of Real Estate Cadastre and Geodesy

RECLAMATION OF LAND CONTAMINATED WITH OIL ANDPETROLEUM PRODUCTS

Purpose of the lesson learn to develop systems of reclamation measureslands contaminated with oil and petroleum products.

GENERAL INFORMATION

In conditions of increased in the XX century anthropogenic load on the biosphere of the planet, the soil, being an element of the natural system and being in dynamic equilibrium with all other components, is subject to degradation processes. One of the most typical problems of our time is pollution by oil and petroleum products. soil cover territories as a result of emergency situations during oil production, transportation and refining.

Currently, individual oil-producing territories are approaching areas of environmental disaster due to environmental conditions. There is a threat of sustainable and often irreversible transformation of the operating conditions of natural systems and changes in the quality of life over large areas in different natural areas from the Far North to the south of the country. There are profound changes in almost all components of the environment: soils and soil structure, soils and subsoil, surface and groundwater, biota and air.

The oil industry ranks third among 130 industries in terms of environmental hazards modern production(Panov et al., 1986).

Since at the current level of development of the oil production and oil refining industry it is not possible to eliminate its impact on the environment, there is a need to reclaim lands contaminated with oil, oil products and highly mineralized oilfield wastewater (EPW).

Soil pollution with oil and non-carbon dioxide differs from many other anthropogenic impacts in that it does not produce a constant, but, as a rule, a “volley” load on the environment, causing a quick response. When assessing the consequences of such pollution, it is not always possible to say whether the economy will return to a stable state or will deteriorate irreversibly. In all activities related to the elimination of the consequences of pollution and the restoration of disturbed lands, it is necessary to proceed from the main principle: not to cause greater harm to the economy than that already caused by pollution.

The concept of economic recovery is based on this principle. E e is the essence of m maximum mobilization of external morning resources for recovery their original f oz.

Currently, the reclamation of oil-contaminated lands in Bashkortostan is carried out, as a rule, without sufficient scientific justification. Elimination of the consequences of oil spills is often carried out in such a way that the fertile layer of soil is irreversibly destroyed, for example, by burning oil, backfilling contaminated areas with soil, or removing contaminated soil to dumps.

1 Methodological provisions

1.1 Remediation methods

Remediation methods used in foreign and domestic practice can be divided into four groups: physical, physicochemical, chemical and biological.

Physical methods include mechanical removal of oil-contaminated and bituminized soil layers containing more than 5% carbon from petroleum products (Yakubov, 1989), collection of petroleum products from the surface using a hydraulic pump ( Hinchel et al., 1988), mixing contaminated soils with clean soil to reduce the content of oil and petroleum products (Abduev, Askerov, 1979; Akhmedov et al., 1988; Ismailov, Pikovsky, 1988).

A number of authors propose to intensively aerate oil-contaminated soils using deep plowing, loosening, disking, and harrowing (Samosova et al., 1979; Anderson, Propadushchaya, 1979, Askerov, 1982; Oborin et al., 1988).

Balch Thomas (1993) proposes intensive collection of contaminated soil into covered piles 4 x 5 m high and up to 40 m wide, at the base of which there is a network of perforated pipes for supplying hot air. As a result of diffusion, heated air picks up hydrocarbons and volatile organic compounds.

N asler Anders (1989) considers the possibility of using cleaning methods by heating the soil to a temperature of 700°C or using a high-pressure water jet. Heimhard Hans - lürgen (1987) suggests using a high-pressure water-air jet. Weston Roy F. (1998), Matig J ., T r ü benbach G . (1991), Joseph E. Musul (1993) use soil heating technology, which evaporates moisture and organic matter. Jorgenson Torre M., Krizan Larry W et. al . (1991) developed step-by-step technology cleaning up oil-contaminated lands in Alaska. Before the soil froze, the oil was removed mechanically and by washing; in the summer of the following year, the soil was fertilized, aerated, and a certain humidity was created, which contributed to favorable conditions for the decomposition of oil. As a result of these measures, the content of oil hydrocarbons decreased by 94% from the initial level.

Physico-chemical methods involve the use of specially selected surfactants (dispersants, dispersants, etc.) and auxiliary substances that affect the change in the state and colloidal dispersed structure of suspended particles in the oil and water phases.

For the cleaning large territories contaminated with harmful man-made compounds, it is proposed to use widespread natural sorbents of organic origin (peat, moss, black soil, coal), clays and clayey materials with a high absorption capacity in relation to pollutants.

Hasler Anders (1989) proposes burning contaminated soils with the simultaneous addition of binders; after heat treatment, the resulting conglomerate is used as a building material, a Rez D . H . (1993) uses Portland cement to neutralize liquid and solid hydrocarbons, while the hydrocarbon is isolated from contact with the environment.

Punt et al. (1991) propose the extraction of soil-polluting petroleum products with a distilled fraction of natural condensate and hexane, and Bulman et al (1993) and Greiner D (1994) chemical saturation of soil with oxygen to restore its biological activity. Hinchel R. E., Downey D. C . et al. (1998) showed the possibility of using water injection enriched with oxygen or containing hydrogen peroxide.

A major role in accelerating the decomposition of oil and oil products in the soil belongs to mineral and organic fertilizers (Samosova et al., 1979; Demidenko et al., 1983; Abzalov et al., 1988; Gainutdinov et al., 1988, Tishkina, 1990).

The use of nitrogen fertilizers is especially important, because In the case of oil pollution, a large amount of C is introduced into the soil, sharply changing the ratio C:N . For the normal development of microorganisms, 1 part nitrogen requires 10 parts carbon, in dirty conditions up to 400 x 420 ( Odu, 1978).

Biological method is the most effective and ecological method reclamation of oil-contaminated soils. They include the use of biological products and biostimulants for the degradation of oil and petroleum products.

In the decomposition of oil in soil, the main and decisive importance is the functional activity of the complex of soil microorganisms, ensuring complete mineralization of oil and oil products to carbon dioxide and water. The main contribution to this process is made by microorganisms capable of using hydrocarbons as the only source of organic matter andenergy. The type of soil, its mineral and organic composition, humidity, aeration, and temperature also affect the rate of degradation of oil hydrocarbons. Based on the ability of microorganisms to use petroleum hydrocarbons and other xenobiotics, a method of biocorrection of pollution has been proposed, which includes the following approaches:

1. activation of the degrading ability of microflora, naturally contained in contaminated soil, by introducing nutrients, co-metabolized substrates, oxygen biostimulation;
2. introduction into contaminated soil of specialized microorganisms, previously isolated from various contaminated sources or genetically modified biosupplementation.

By using biological method Based on the use of natural strains of microorganisms, within 3 years of reclamation it is possible to completely restore the fertility of oil-contaminated soils at a pollution level not exceeding 10 x 15% of crude oil by weight of the soil. In the case of higher concentrations of pollutants, it is advisable to combine bioremediation with physical andphysical and chemical cleaning methods.

The species diversity of oil-oxidizing bacteria is great. Very effective biological products have been created based on strains of various bacteria and their associations: Rhodotrin, Ekoil, Putidoil, etc.

The physicochemical and chemical methods are also simulating to a certain extent. Various food additives and surfactants, yeast production waste, fish flour, whey, protein and vitamin plant waste, activated sludge, nitrogen, phosphorus and potassium also serve as biostimulants. mineral fertilizers, traditional manure and even, as research by N.A. Kireeva, liquid wastewater from livestock complexes and other wastewater that is disposed of in agricultural irrigation fields.

The role of earthworms in the decomposition of oil is known. Kibardin et al. (1989) showed that earthworms ingest oil in the soil and make it available to microorganisms.

Sowing alfalfa and other legumes and grasses with a branched root system into oil-contaminated soil helps accelerate the decomposition of hydrocarbons (Aliev et al., 1977; Gudin, Syratt, 1975; Lee Eusiand , 1993). The positive impact of crops of agricultural plants, and in particular perennial grasses, is explained by the fact that with their developed root system they help improve the gas-air regime of contaminated soil, enrich the soil with nitrogen and biologically active compounds released by the root system into the soil during plant life. All this stimulates the growth of microorganisms and, accordingly, accelerates the decomposition of oil and petroleum products. In this regard, one cannot fail to take into account the ability of plants themselves to decompose various classes of petroleum hydrocarbons (Ugrekhelidze, 1976) or adsorb them ( Cunningham Scott et al., 1995).

1.2 Integrated land reclamation technology,

Oil contaminated

The technology for reclamation of land contaminated with oil depends on many factors: the concentration of oil in the soil, the type of oil, the availability of remediation means - biological products, chemical ameliorants, technical means, etc. Based on research and generalization of experience in the reclamation of lands contaminated with oil, the Institute of Biology of the Ural Scientific Center of the Russian Academy of Sciences, together with BashNIPIneft, developed a guideline document “Reclamation of technogenically disturbed lands during oil production”, which was approved by the relevant government agencies and was offered to the enterprises of ANK Bashneft for use in the restoration of lands polluted by oil and petroleum products. Russian Federation patents were also received for the invention “Method for cleaning soils from oil pollution» .

According to the proposed scheme (Figure 1) of the main measures for the remediation of oil-contaminated soils, a reclamation survey of the contaminated area is first carried out, the boundaries of the area and all those factors on the basis of which remediation methods are selected are clarified.

Picture 1 Scheme of main activities for the reclamation of oil-contaminated lands

The main means of reclamation of oil-contaminated lands are the use of biological preparations and the activation of indigenous soil microflora against the background of various agrotechnical and phytomeliorative measures aimed at optimizing trophic and physicochemical conditions for the life of microorganisms that consume oil hydrocarbons.

Effective use of biological products is possible when the concentration of petroleum products in the soil is no higher than 1015%. Therefore, at the first stage of reclamation, when the oil content is higher than the oil capacity of the soil, the spilled oil along with some part of the surface layer of soil is mechanically collected and transported to earthen (oil sludge) pits. After separating oil from the soil, using surfactants, before starting biological reclamation at the landfill, it is necessary to carry out a series of agrotechnical measures - intensive loosening, moistening, application of complex mineral and organic fertilizers. You can also leave the soil to fallow with periodic loosening and subsequently carry out phytomelioration, using mainly as green manure legumes. If the oil content in contaminated soil is in a concentration of up to 105%, you can immediately begin agrotechnical interventions (loosening, applying fertilizers and biostimulants) followed by the application of biological products. If the oil content in the soil is less than 5%, you can begin phytomelioration immediately or through the fallow stage.

Reclamation is considered complete when the oil content in the soil decreases to 0.1% and the formation of grass with a projective cover of at least 80%. When soils are contaminated with crude oil, which contains a significant amount of non-carbon dioxide, chemical ameliorants are included in the remediation scheme. On initial stage If possible, the soil is washed from salts, then gypsum is applied, then the agrotechnical and biological methods of reclamation provided for in the system of measures are carried out.

2 order of task completion

2.1 Main reclamation measures

oil-contaminated soils

First stage agrogeochemical.

At this stage, the process of weathering, evaporation and partial destruction of light fractions, photo-oxidation, partial restoration of microbiological communities and soil animals occurs. Some of the components turn into a solid product, which improves the water-air regime.

1. Collecting oil from the surface (bulldozers, excavators), pumping it out with pumps.
   1. Transportation and storage in oil sludge pits for subsequent processing.

3. Preparing the site by partial or complete leveling (if necessary) the soil is cleared of debris, accident liquidation waste and left for self-purification and natural transformation of oil for 1.0 x 1.5 years.

1. During the first stage, if there is no danger of erosion, it is necessary to loosen the soil (ploughing to a depth of 10 x 20 cm) 2 x 3 times after the soil reaches physical ripeness in the spring.
   1. In winter, snow retention is necessary, and in spring, regulation of snow melting is necessary.
      1. Application of complex mineral fertilizers(N, P, K), not less than 90 kg active per 1 hectare.
      2. At this stage, when soil contamination is less than 10% (by weight), biological products are used, including biostimulants and bioadditives. When soils are slightly polluted, the application of biological products is not economically feasible. It should be limited to agrotechnical methods and biostimulation.
      3. At the agrotechnical stage, control is carried out for possible contamination of groundwater with oil.
      4. At the end of stage 1, an analysis of the residual oil content in the soil is carried out. The degree of natural overgrowth is determined.

Second phase biological.

1. 1st stage of the biological stage trial sowing of grasses. The purpose of this event is to assess the residual phytotoxicity of soils, intensify the processes of oil biodegradation, and clarify the timing of the transition to the final stage.
   1. Before test sowing, the soil is plowed (loosened, disced). Mostly legumes are sown (peas, alfalfa, sweet clover and etc.).
      1. 2nd stage of biological remediation: sowing of perennial grasses is carried out 1-3 years after contamination. This stage begins if the trial sowing has sprouted on at least 75% of the area.
         1. Before sowing perennial grasses, the soil is loosened and organic fertilizers and biostimulants are applied. It is better to apply mineral fertilizers in the form of fertilizing 2-3 times.
         2. Recommended grasses for the forest-steppe zone: meadow fescue, meadow timothy, red clover, awnless brome, cocksfoot, blue-hybrid alfalfa. For the wall zone: comb wheatgrass, yellow hybrid alfalfa, yellow sweet clover, hair grass, fibrous regneria.
         3. Perennial herbs are grown for at least 2 years. It is not recommended to use green mass for feed purposes; it is better to plow it into the soil as green manure.
         4. Reclamation is considered complete if the growth of grasses and the formation of grass stands is normal from an agronomic point of view and more than 80% of the area is overgrown. The oil product content should not exceed 0.1%.

3 tasks for self-employment

Develop a system of measures for the reclamation of contaminated lands, taking into account the level of oil pollution (see Table 1).

Table 1 Classification of soils according to the degree of oil contamination

* sanitary standard ≤0.1%

The technological map is drawn up in accordance with Table 2:

Table 2 Technological map

Conclusions:

Form of control. Developed routing on the reclamation of oil-contaminated lands with conclusions are provided to the teacher and assessed with an interview.

4 Questions for self-control of knowledge

1 What methods are used to reclaim land contaminated with oil and petroleum products?

2 What are the main biological products used in the reclamation of lands contaminated with oil and petroleum products?

3 Main measures for reclamation of lands contaminated with oil and petroleum products?

4 Describe modern methods cleaning land from oil products.

5 Which method is the most effective for the reclamation of land contaminated with oil and petroleum products?

BIBLIOGRAPHICAL LIST

1 Gabbasova, I.M. Soil degradation and reclamation Ba w kortostan [Text] / I.M. Gabbasova. Ufa, Gilem, 2004. 284 p.

2 Golovanov, A. I. Reclamation of disturbed lands [Text]: textbook. manual / A. I. Golovanov, F. M. Zimin, V. I. Smetanin; edited by A. I. Golovanova. M.: KolosS, 2009. 325 p.

3 Fundamentals of environmental management [Text]: textbook / A.I. Goal O Vanov [and others]. M.: Kolos, 2001. 263 p.

4 Soils of Bashkortostan [Text]. T.2. Ufa: Gilem, 1997. 328 p.

5. Sadovnikova, L. K. Ecology and environmental protection in chemical e com pollution [Text]: textbook. allowance / L.K. Sadovnikova, D.S. Orlov, I.N. Lozanovskaya. 3rd ed., p e rework M.: Higher. school, 2006. 334 p.

6 System of agricultural production in the Republic of Ba w kortostan [Text]. Ufa, Gilem, 1997. 612 p.

7 Smetanin, V.I. Reclamation and arrangement of bunks at occupied lands [Text]: textbook / V.I. Sour cream. M.: Kolos, 2000. 96 p.

RECLAMATION OF OIL CONTAMINATED LAND

Thanks to many years of practice in reclamation work, a significant variety of different methods for restoring soils contaminated with oil and petroleum products have now been accumulated in the arsenal of environmental specialists: from basic mechanical collection of pollutants to the use of highly effective hydrocarbon-oxidizing microorganisms (HOM), including genetic engineering products. With regard to methods based on the introduction into soil of strains of active oil-absorbing crops, experts still do not have a consensus due to the unpredictability of the results of the introduction of strains due to their competition with indigenous UOM, which are widespread in all types of soils and are an integral component of soil microbiocenosis. Peat soils of the northern regions are no exception and contain a significant amount of HOM, the number of which after oil spills can increase by 2-3 orders of magnitude and amount to at least 107 - 108 cells per 1 g of soil. Therefore, during reclamation peat soils the most preferable is the use of methods for stimulating the metabolic activity of the soil’s own native microflora by optimizing its physicochemical conditions. For example, one of these methods developed by NTO<Приборсервис>, allows, through a set of agrotechnical measures and the addition of aluminosilicate minerals, to achieve a 70-80% degree of soil purification in one growing season (Fig. 1)

b)

Figure 1. View of the site before (a) and after (b) reclamation

As is known, soil contamination with nitrogen-depleted oil leads to the establishment in the soil of a regime of severe nitrogen deficiency for microorganisms, which is one of the main limiting factors for the rapid self-healing of soil. The use of nitrogen mineral fertilizers eliminates this limitation.

It is known that in oil-contaminated soils, in many cases, a sharp increase in the processes of biological nitrogen fixation is observed. At the same time, ongoing studies of microbiological processes in oil-contaminated soil have shown that the activity of UOM is directly dependent on the intensity of the influx of atmospheric nitrogen into the soil, carried out by nitrogen-fixing microorganisms.

The reasons for the inhibition of microbiological nitrogen fixation in arable soils by nitrogen fertilizers are quite understandable: enriching the soil with available nitrogen makes the process of binding molecular nitrogen energetically unfavorable for nitrogen-fixing microorganisms, and they switch to a substrate type of nutrition. It is well known from agricultural practice that the application of even medium doses of mineral nitrogen fertilizers leads to a sharp inhibition of the processes of biological nitrogen fixation in soils.

Contrary to existing ideas about the stimulating effect of nitrogen fertilizers on SOM, microbiological soil analysis data revealed an inverse relationship between the number of these microorganisms in the soil and the amount of mineral fertilizers applied. For example, smallest number UOM was recorded in the control variant with the maximum starting dose of fertilizers (500 kg/ha of azophosphate + 500 kg/ha of ammonium nitrate), and the highest - in the 2nd variant with the minimum starting dose of fertilizers (150 kg/ha of azophosphate + 150 kg/ ha of ammonium nitrate).

Analysis of Azotobacter activity also revealed an inverse relationship between this indicator and the starting dose of nitrogen fertilizers. Wherein maximum level activity throughout the entire observation period was observed in the variant with a minimum starting dose of fertilizers. In the control variant with the highest starting dose, the activity of Azotobacter was not recorded at all.

Repeated application of nitrogen fertilizers to both variants, regardless of the dose, led to complete suppression of Azotobacter activity. And only approximately 5-6 days after repeated application of fertilizers, the activity of Azotobacter began to increase again.

Thus, even obviously low doses of nitrogen mineral fertilizers from the point of view of specialists in the field of remediation of oil-contaminated soils, not exceeding 500 kg/ha, led to a noticeable suppression of the activity of nitrogen-fixing microorganisms and, as a consequence, a reduction in the influx of free nitrogen from the atmosphere into the soil, environmentally absolutely safe and also free.

In general, attention is drawn to the direct relationship between the activity of nitrogen-fixing and hydrocarbon-oxidizing microorganisms, as well as the degree of oil degradation according to the experimental variants and, at the same time, inverse relationship all these indicators depend on the amount of mineral fertilizers applied.

Biological nitrogen fixed by microorganisms from the atmosphere has a more significant impact on the rate of microbiological destruction of petroleum products in the soil compared to nitrogen introduced into the soil as part of mineral fertilizers. In this regard, it is very noteworthy that the repeated application of azophosphate and ammonium nitrate practically did not lead to a decrease in the content of residual oil in the soil and turned out to be ineffective. There is also a high probability that the complete suppression of Azotobacter activity observed in this case stopped the further course of oil destruction processes in the soil.

Analysis of the level of phytotoxicity of the soil showed that the control variant was distinguished by minimal indicators of seed germination and maximum indicators of phytotoxicity. The lowest level of toxicity was noted in the variant with a minimum starting dose of mineral fertilizers.

The high level of toxicity in oil-contaminated soil may be due to the accumulation of early stages microbiological destruction large quantity petroleum acids and other products of primary oil degradation that have high degree toxicity for both plants and most microorganisms.

Chemical pollution of geosystems and principles of remediation of contaminated lands. Pollution in its essence, whether natural or

anthropogenic is the introduction (injection) of various substances into the abiotic and biotic components of the geosystem, causing negative toxic-ecological consequences for the biota. When studying pollution processes and their description, it is necessary to rely on knowledge about the properties of the geosystem, intercomponent connections and environmental laws.

Violation of the gas, concentration, redox functions of biota, causing the loss of its geochemical self-purification;

Change bio chemical composition biota products, causing disruption of the vital functions of chains in a given geosystem and beyond its boundaries during the alienation of biological products;

Decrease in biological productivity of the geosystem;

Reducing the information content of the geosystem, i.e. destruction of the gene pool necessary for its existence.

Pollution can be caused by natural processes, but is often the result of human activity. Anthropogenic soil pollution can be divided into municipal, agricultural, industrial and military.

Communal pollution is associated with the functioning settlements, in which the products of life and activity of people in their places of settlement are discharged into the natural environment: wastewater, household waste, garbage, etc.

Agricultural pollution occurs over large areas as a consequence of the use of means to combat diseases and pests of cultivated plants, weeds (pesticides, insecticides, herbicides), and the application of increased doses of mineral and organic fertilizers. This also includes pollution when used for irrigation, including industrial wastewater, for fertilizing and moisturizing purposes, and when used for irrigation of water with high mineralization.

Industrial pollution over large areas occurs when vapors, aerosols, dust or dissolved pollutants enter the soil through the atmosphere or with rain and snow. Local pollution occurs in areas where dumps, waste, etc. are stored.

Military pollution occurs during combat operations, maneuvers, and testing of military equipment.

All components of the geosystem can be objects of pollution, but the main attention should be paid to soil pollution for the following reasons:

Soil, being by definition V.V. Dokuchaev's outer shell of land, primarily absorbs the impact of many pollutants, accumulates a large volume of pollutants;

Contaminated soil, being a habitat for agricultural plants, predetermines the possibility of disruption of their vital functions and other related consequences;

The soil, as an active organomineral body, is capable of significantly transforming pollutants, binding them into immobile forms and even destroying them;

The soil, transforming the flows of moisture and substances contained in it, regulates, within certain limits, the pollution of underlying rocks, underground and associated surface waters, i.e. performs an environmental function.

To properly understand the processes of contamination of components of geosystems and develop methods for their reclamation, it is useful to use the theory of biogeochemical barriers that objectively exist in nature and are created by man (see 2.4).

Reclamation of lands contaminated with heavy metals. Soil contamination with heavy metals leads to the formation of an acidic or alkaline reaction of the soil environment, a decrease in the exchange capacity of cations, loss of nutrients, changes in density, porosity, reflectivity, the development of erosion, deflation, a reduction in the species composition of vegetation, its suppression or complete death .

Before reclamation of such lands begins, it is necessary to establish the source and causes of pollution, take measures to reduce emissions, localize or eliminate the source of pollution. Only under such conditions can high efficiency of reclamation work be achieved.

The guideline for developing the composition of land reclamation work is, first of all, the priority substance that causes deterioration of the ecological state of soils and the quality of agricultural products, and the expected mobility of other hazardous substances should be regulated by special or complex measures.

Reclamation of lands contaminated with heavy metals is carried out using the following methods:

1) Cultivation of pollution-resistant cultivated and wild plants. On contaminated agricultural lands, a reorganization and reorientation of agricultural production is being carried out through the introduction of a new structure of crop production, and they are moving to growing crops that are not directly used for human food.

2) Reclamation of soils with the help of plants (phytoremediation) capable of accumulating heavy metals in vegetative organs. It has been established that during the growing season, a tree along a highway is capable of accumulating an amount of lead equal to its content in 130 kg of gasoline, therefore, in populated areas with contaminated areas, it is advisable to collect and dispose of leaf litter.

To clean soils from zinc,

For lead and cadmium, it is necessary to grow large knotweed, for lead and chromium - mustard, for nickel - buckwheat, etc., if contaminated with radioactive isotopes, you can use vetch, peas, alfalfa, shag. 3) Regulation of the mobility of heavy metals in the soil. The absorption of heavy metals by plants depends on the content of their mobile forms in the soil. The existence of mobile forms is determined by the properties and fertility of soils, biogeochemical processes, intensity and volumes of heavy metals

into the soil, carried out by plants. The behavior of heavy metals in soil and methods for managing their content follow from the theory of geochemical barriers, and remediation of contaminated soils comes down to creating additional barriers, managing existing barriers, or weakening some of them.

Soils that are heavy in mechanical composition and have high fertility contain fewer mobile forms of heavy metals than soils that are light and unproductive. Many of the metals belonging to the first hazard class form poorly soluble compounds in a neutral soil environment, and easily soluble ones in an acidic environment. Cadmium is most mobile in an acidic environment and weakly mobile in a neutral and alkaline environment. Chemical compounds that are mobile in an acidic environment include the cations Zn, Cu, Pb, Cd, Sr, Mn, Ni, Co. Those that are mobile in a neutral and alkaline environment are Mo, Cr, As, V, Se.

To regulate the mobility of heavy metal compounds in the soil, liming, gypsum, and the addition of organic and mineral

When reclaiming lands contaminated with heavy metals, considerable attention is paid to the maintenance and formation of sparingly soluble compounds in the soil. For this, in addition to the above methods, artificial and natural adsorbents are used. Natural ones include peat, moss, chernozem soils, sapropel (lake silt), bentonite clays, glauconite sands, clinoptilolites, opoka, tripoli, diatomites. Artificial adsorbents are created as a result of activation or mixing of natural adsorbents, for example, activated carbon, aluminosilicate and iron-aluminosilicate adsorbents, carbon-aluminum gels, ion-exchange resins, polystyrene.

4)Regulation of ratios chemical elements in the soil. This method is based on the antagonism and synergism of chemical elements, i.e. when one element prevents or promotes the entry of another into the plant, for example, zinc prevents the entry of mercury, and excess phosphorus leads to a decrease in the toxicity of zinc, cadmium, lead and copper, the presence of calcium can create antagonistic conditions for some metals, and synergistic conditions for others, in fertile soil. In soil, zinc and cadmium resist the fixation of copper and lead, and in low-fertility soil the process can develop in the opposite direction.

5) Creation of a remediation layer, replacement or dilution of a contaminated soil layer can be carried out using a multi-layer scheme, as well as by applying one layer of soil to a previously screened or unscreened contaminated surface. Dilution of the contaminated layer is carried out by digging clean soil with subsequent mixing; dilution can also be carried out using deep plowing, when the top contaminated layer is mixed with the clean bottom layer. They use the removal of the contaminated layer and its processing, or the removal of contaminated soil with subsequent cleaning and return, but usually such operations are carried out in small areas; they are an expensive method of reclamation.

For the reclamation of large areas, including residential and recreational areas of settlements, agricultural lands experiencing long-term pollution, the following comprehensive scheme can be applied:

Significant reduction in emissions from enterprises (technological barrier);

Strict dosing of chemical plant protection products, optimal regulation of nutrient and acid regimes of the soil (technological barrier);

Management of water migration flows through the organization of surface runoff, the creation of storm sewers, drainage systems and subsequent

wastewater treatment (mechanical barrier).

Strengthening the sorption barrier of the soil layer is necessary to significantly reduce the amount of mobile compounds of heavy metals that enter plants and contaminate products, while at the same time the total amount of metals in the soil may not only not decrease, but even increase due to a decrease in mobility.

In addition to this, minimizing the infiltration component of the water regime of the soil layer under conditions of watering green spaces, lawns, gardens, agricultural and other crops, i.e. implementation of measures aimed, on the one hand, at some weakening of the hydrophysical barrier, but on the other hand, necessary to consolidate the effect of strengthening the sorption barrier.

Reclamation of lands contaminated with oil and petroleum products. The scope of work depends on the degree of contamination. With minor contamination, they activate the activity of soil microorganisms to destroy hydrocarbons. This includes loosening the soil, applying lime, gypsum, high doses of organic and mineral fertilizers followed by plowing, creating a mulched surface from highly nutrient mixtures, sowing oil-tolerant plants at higher rates; possible options for

changes in complex complexes: NPK + manure; NPK + lime; NPK + lime + manure. Resistant forage plants are sown, the use of which must be strictly controlled, since they can accumulate carcinogens such as polycyclic aromatic hydrocarbons.

In case of severe pollution, engineering-ecological systems are constructed. The creation of such systems is due to the high mobility of petroleum products in the components of geosystems, especially with long-term soil contamination, and the formation of large areas of free and bound petroleum products at the interface between the aeration zone and groundwater. Such anthropogenic deposits of petroleum products are formed near fuel and lubricant warehouses, oil depots and oil refineries. They cause the danger of polluting not only soils but also ground and surface waters. Therefore, the tasks of the engineering-ecological system are the removal of mobile oil products, soil reclamation, protection of rivers and water intakes from pollution by oil products while simultaneously localizing sources of pollution.

Over a long period of time (several decades), such systems prevent the spread of the unrecoverable part of petroleum products from deposits into urban water intakes and rivers, regulate the concentration of light hydrocarbons in the aeration zone and reduce fire danger, and provide management of hydrochemical and biological regimes of soils based on environmental monitoring , groundwater and surface water.

The engineering and environmental systems include embankment dams, a wall in the ground, injection wells, horizontal and vertical drainage, production wells, as well as measures for technical and biological reclamation of contaminated lands.

Embankment dams and measures to organize surface runoff are designed to protect the contaminated area from flooding during floods and prevent surface wash-off of oil products; the accumulated surface runoff should be directed after preliminary biodestruction and post-treatment into the water circulation systems of industrial enterprises.

A wall in the ground, which is an anti-filtration curtain and is installed along the contour of the oil deposit; localizes the area of ​​contamination. Injection wells provide lifting and displacement of mobile oil products to production wells, which pump out oil products and contaminated oil within the contour of the oil deposit. The groundwater followed by cleaning.

After removing mobile oil products, soils are further purified. In this case, various biodestructors are used, for which they create optimal water, air, thermal and food regimes, using

irrigation, drainage, organic and mineral fertilizers. They constantly monitor the level of pollution and the quality of agricultural products.

Soils with very high level oil-contaminated contaminants are sent for processing in order to extract the extractable part of petroleum products, after which they are reclaimed in stationary or field conditions.

Technogenic flows of hydrocarbons in landscapes, especially oil with salt waters, lead to loss of land productivity, vegetation degradation, and the formation of badlands. Soils and soils heavily contaminated with oil and petroleum products are characterized by unfavorable structural and physicochemical properties for their use for economic purposes. By releasing sorbed hydrocarbons in the form of dissolved products, emulsions or evaporations, contaminated soils serve as a constant secondary source of pollution of other environmental components: water, air and plants.

Land reclamation is a set of measures aimed at restoring the productivity and economic value of disturbed and contaminated lands, as well as improving environmental conditions. The task of reclamation is to reduce the content of petroleum products and other substances associated with them toxic substances to safe levels, restore land productivity lost as a result of pollution.

results scientific research on soil reclamation in various regions of the world are published by many domestic and foreign authors. A review of these works, along with new data, was published in a book by a team of authors (Recovery of oil-contaminated..., 1988). It should be noted that studies carried out in different soil and climatic conditions and with different methods often give ambiguous or directly opposite results. The period of observation is also insufficient, which does not allow taking into account the aftereffect of the measures taken. Currently, several fundamentally different methods are used for the remediation of soils contaminated with oil and petroleum products.

Thermal and thermoextraction methods. Petroleum products are removed by direct combustion on site or in special installations. Most cheap way- burning of petroleum products or oil on the soil surface. This method is ineffective and harmful for two reasons: 1) combustion is possible if the oil lies on the surface in a thick layer or is collected in storage tanks; soil or soil saturated with it will not burn; 2) in the place of burned petroleum products, soil productivity, as a rule, is not restored, and among the combustion products remaining in place or dispersed in environment, many toxic, in particular carcinogenic, substances appear.

Cleaning soils and soils in special installations by pyrolysis or steam extraction is expensive and ineffective for large volumes of soil. Firstly, large excavation for passing soil through installations and placing it in place, resulting in the destruction of the natural landscape; secondly, after heat treatment, newly formed polycyclic aromatic hydrocarbons, a source of carcinogenic hazard, may remain in the cleaned soil; thirdly, there remains the problem of disposal of waste extracts containing petroleum products and other toxic substances.

Extraction cleaning of soil “t-v^i” with surfactants. The technology for cleaning soils and groundwater by washing them with surfactants is used, for example, at US Air Force bases. This method can remove up to 86% of oil and petroleum products; it is most effective for deep-lying aquifers through which polluted water is filtered groundwater. Its use on a large scale is hardly advisable, since surfactants themselves pollute the environment and there will be a problem with their collection and disposal.

Microbiological remediation with the introduction of microorganism strains. Cleaning soils and soils by introducing special cultures of microorganisms is one of the most common methods of reclamation, based on the study of the processes of biodegradation of oil and petroleum products. The current level of knowledge of microorganisms capable of assimilating hydrocarbons in natural and laboratory conditions allows us to assert the theoretical possibility of regulating the processes of cleaning up oil-contaminated soils and soils. However, the multi-stage nature of the biochemical processes of hydrocarbon decomposition different groups microorganisms, complicated by the diversity of the chemical composition of oil, makes it difficult to regulate the sustainable process of their decomposition. When using microbiological methods, complex problems arise in the interaction of populations introduced into the soil with natural microflora. Certain difficulties are associated with the lack of modern technical means and methods for continuous monitoring and regulation of the multifactorial system substrate - microbiocenosis - metabolic products in real soil conditions.

The use of bacterial preparations obtained on the basis of monocultures isolated from natural strains in certain regions should be approached with caution. It is known that an entire microbiocenosis with a characteristic structure of trophic connections and energy metabolism takes part in the decomposition of oil, participating in the decomposition of hydrocarbons at different stages by specialized ecological-trophic groups (Ismailov, 1988). Therefore, the introduction of monoculture can only lead to an apparent effect. In addition, its suppression of local microbiocenosis can negatively affect the entire soil ecosystem and cause more harm to it than oil pollution. Microbiological preparations work effectively, as a rule, under conditions of sufficient moisture in combination with agrotechnical practices (Dyadechko et al., 1990). But these same techniques stimulate the development of the same strains in the soil in combination with the entire microbiocenosis, which accelerates the natural process of self-purification.

Reclamation methods based on the intensification of self-purification processes. Reclamation methods that create conditions for the operation of the natural self-purification mechanisms of soils, suppressed due to severe pollution, are the most optimal and safe for soil ecosystems. Research by a number of laboratories was devoted to the development of this concept for various natural zones (Restoration of oil-contaminated areas 1988).

When assessing the consequences of oil pollution, it is not always possible to say whether the landscape will return to a stable state or will be irreversibly degraded. Therefore, in all activities related to the elimination of the consequences of pollution and the restoration of disturbed lands, it is necessary to proceed from the main principle of not causing more harm to the natural environment than that already caused by pollution.

The essence of the concept of landscape restoration is the maximum mobilization of their internal resources to restore their original functions. Self-healing and reclamation are an inseparable biogeochemical process. Reclamation is a continuation (acceleration) of the self-purification process, using natural reserves - climatic, landscape-geochemical and microbiological.

Self-purification and self-healing of soil ecosystems contaminated with oil and oil products is a staged biogeochemical process of transformation of pollutants, associated with a staged process of restoration of the biocenosis. For different natural zones, the duration of individual stages of these processes is different, which is mainly due to soil-climatic conditions. The composition of the oil, the presence of accompanying salts, and the initial concentration of pollutants also play an important role.

The process of natural fractionation and decomposition of oil begins from the moment it reaches the soil surface or is discharged into reservoirs and streams. The patterns of this process over time were clarified in general outline during a long-term experiment conducted in model areas in forest-tundra, forest, forest-steppe and subtropical natural zones. The main results of this experiment are presented in the previous chapter.

There are three most general stages of oil transformation in soils: 1) physicochemical and partially microbiological decomposition of aliphatic hydrocarbons; 2) microbiological destruction of mainly low-molecular structures of different classes, new formation of resinous substances; 3) transformation of high-molecular compounds: resins, asphaltenes, polycyclic hydrocarbons. The duration of the entire process of oil transformation in different soil and climatic zones is different: from several months to several tens of years.

In accordance with the stages of biodegradation, gradual regeneration of biocenoses occurs. These processes occur slowly, at different rates, in different tiers of ecosystems. The saprophytic complex of animals is formed much more slowly than microflora and plant cover. As a rule, complete reversibility of the process is not observed. The strongest outbreak of microbiological activity occurs during the second stage of oil biodegradation. With a further decrease in the number of all groups of microorganisms to control values, the number of hydrocarbon-oxidizing microorganisms remains abnormally high for many years compared to the control.

As was established in experiments with the perennial grass Bonfire, the restoration of normal conditions for its growth on oil-contaminated soil depends on the level of initial pollution. In the southern taiga zone (Perm Kama region), with an oil load on the soil of 8 l/m2, already a year after a single act of pollution (without the participation of salts), the cereal could grow normally in a spontaneously recovering ecosystem. At higher initial loads (16 and 24 l/m2), normal plant growth was not restored, despite the progressive processes of oil biodegradation.

Thus, the mechanism of self-healing of an ecosystem after oil pollution is quite complex. To control this mechanism, it is necessary to determine the boundaries of the metastable state of the ecosystem, in which at least partial self-healing is still possible, and to find effective ways to return the ecosystem to these boundaries. Solving this problem will help determine the optimal ways to reclaim oil-contaminated soil ecosystems.

As stated above, mechanical and physical methods cannot ensure complete removal of oil and petroleum products from the soil, and the process of natural decomposition of contaminants in soils is extremely long. The decomposition of oil in soil under natural conditions is a biogeochemical process in which the main and decisive importance is the functional activity of the complex of soil microorganisms that ensure complete mineralization of hydrocarbons to CO2 and water. Since hydrocarbon-oxidizing microorganisms are permanent components of soil biocenoses, a natural desire arose to use their catabolic activity to restore oil-contaminated soils. It is possible to accelerate the cleanup of soils from oil pollution with the help of microorganisms mainly in two ways: 1) by activating the metabolic activity of natural soil microflora by changing the corresponding physicochemical environmental conditions (well-known agrotechnical methods are used for this purpose); 2) introducing specially selected active oil-oxidizing microorganisms into contaminated soil. Each of these methods is characterized by a number of features, and their practical implementation often encounters technical and environmental difficulties.

With the help of agricultural techniques, it is possible to accelerate the process of self-purification of oil-contaminated soils by creating optimal conditions for the manifestation of the potential catabolic activity of UOM, which are part of the natural microbiocenosis. Plowing of oil-contaminated areas is recommended after some time, during which the oil partially decomposes (Mitchell et al., 1979). Treatment is a powerful regulatory factor that stimulates the self-cleaning of oil-contaminated soils. It has a positive effect on microbiological and enzymatic activity, as it helps improve the living conditions of aerobic microorganisms, which dominate in soil quantitatively and in terms of metabolic rate and are the main destructors of hydrocarbons. Loosening contaminated soils increases the diffusion of oxygen into soil aggregates, reduces the concentration of hydrocarbons in the soil as a result of volatilization of light fractions, ensures the rupture of surface pores saturated with oil, but at the same time promotes the uniform distribution of oil components in the soil and an increase in the active surface. Soil cultivation creates a powerful biologically active layer with improved agrophysical properties. In this case, an optimal water, gas-air and thermal regime is created in the soil, the number of microorganisms and their activity increases, and the activity increases soil enzymes, the energy of biochemical processes increases.

In the first weeks and months after contamination, mainly abiotic processes of oil change in the soil occur. The flow is stabilized, partially dissipated, and the concentration decreases, which allows microorganisms to adapt, rebuild their functional structure and begin active oxidation of hydrocarbons. In the first months after contamination, the oil content in the soil decreases by 40-50%. Subsequently, this decline occurs very slowly. The diagnostic signs of residual oil change; the substance, initially almost completely extracted with hexane, is then predominantly extracted with chloroform and other polar solvents.

The first stage lasts, depending on natural conditions, from several months to one and a half years. It begins with the physical and chemical destruction of oil, to which the microbiological factor is gradually connected. First of all, methane hydrocarbons (alkanes) are destroyed. The speed of the process depends on the soil temperature. Thus, in the experiment, the content of this fraction decreased over the course of a year: in the forest-tundra by 34%, in the middle taiga by 46%, in the southern taiga by 55%. In parallel with the decrease in the proportion of alkanes in residual oil, the relative content of resinous substances increases. The second stage of degradation lasts about 4-5 years and is characterized by the leading role of microbiological processes. By the beginning of the third stage of oil destruction, the most stable high-molecular compounds and polycyclic structures accumulate in its composition, with an absolute decrease in the content of the latter.

The first stage of reclamation corresponds to the most toxic geochemical conditions and maximum inhibition of biocenoses. At this stage, it is advisable to carry out preparatory measures: aeration, humidification, localization of pollution. The purpose of these activities is to intensify microbiological processes, as well as photochemical and physical processes decomposition of oil, reducing its concentration in the soil. At this stage, the depth of change in the soil ecosystem and its direction are assessed. natural evolution. The duration of the first stage varies in different zones, in middle lane it is equal to approximately one year.

At the second stage, test sowing of crops is carried out in contaminated areas in order to assess the residual phytotoxicity of soils, intensify the processes of oil biodegradation, and improve the agrophysical properties of soils. At this stage, the water regime and acid-base conditions of the soil are regulated, and, if necessary, desalinization measures are carried out. At the third stage, natural plant biocenoses are restored, cultural phytocenoses are created, and sowing of perennial plants is practiced.

The total duration of the reclamation process depends on soil and climatic conditions and the nature of contamination. This process can be completed most quickly in steppe, forest-steppe, and subtropical regions. In the northern regions it will last longer. Approximately the entire period of reclamation in different natural zones takes from 2 to 5 years or more.

The issue of introducing various ameliorants into the soil, in particular mineral and organic fertilizers, to accelerate the processes of oil decomposition deserves special consideration. The need for such measures has not yet been experimentally proven.

The work (McGill, 1977) discusses the issue of competition between microorganisms and plants for nitrogen in oil-contaminated soil. A number of authors propose adding nitrogen and other mineral fertilizers to the soil in combination with various additives: (lime, surfactants, etc.), as well as organic fertilizers(eg manure). The application of these fertilizers and additives is designed to enhance the activity of microorganisms and accelerate the decomposition of oil. These measures gave positive results in a number of cases, mainly in the first year after their use. At the same time, more distant effects were not always taken into account - the deterioration of the condition of soils and plants in subsequent years. For example, experiments conducted in the Perm Kama region with the addition of mineral fertilizers and lime to contaminated soil showed that two years after contamination, plants on the “fertilized” soil developed no better, and in some places even worse, than on soil with the same contamination, but not containing ameliorants.

Thus, multi-year studies with different types soils and oils, correlated with certain natural conditions. In the meantime, we can recommend the application of ameliorants only at the third, final, stage of reclamation after a thorough chemical study of the soil.

All these questions are difficult to solve purely empirically, since the number of experimental options turns out to be almost infinite. Comprehensive basic research in the field of biogeochemistry and ecology of contaminated soils with the aim of developing a theory of the process and scientific recommendations based on it.

Based on the experimental studies carried out, the following conclusions can be drawn regarding the conditions of transformation and reclamation of oil in soils of different natural zones.

Light gray-brown soils of the dry subtropics of Azerbaijan. The conditions for the transformation of hydrocarbons are characterized by an excess of evaporation over moisture, low horizontal water flow, and increased microbiological and enzymatic activity of soils. The most intense processes of oil transformation occur in the first months after contamination, then they slow down several times. After a year, the amount of residual oil was 30% of the original amount, after four years - 23%. Approximately 30% of the oil, which contains many heavy fractions, mineralizes or evaporates. The rest is converted into poorly soluble metabolic products, which remain in the humus horizon of the soil, preventing the restoration of their fertility. The most effective method of reclamation is to enhance the functional activity of microorganisms by moistening, aeration, adding enzymes, and phytomelioration.

Podzolic-yellow earth and silt-gley soils of humid subtropics. Self-cleaning of soils from oil occurs under conditions of intense surface water water flow, high microbiological activity of soils. Natural cleansing and restoration of vegetation occurs over several months.

Podzolic and sod-podzolic soils of the forest-taiga region of Western Siberia and the Urals. Soil self-purification and oil transformation take place under conditions of increased moisture, which contributes to the horizontal and vertical dispersion of oil in the first period after contamination. Due to water dispersion during the first year, up to 70% of the introduced oil can be removed from the territory and redistributed in the surrounding space. Microbiological and enzymatic activity of soils is lower than in the southern regions. Over the course of a year, approximately 10-15% of the initially applied oil is converted into products of microbiological metabolism. The most effective methods of protection and reclamation are preventing oil spills using artificial and natural sorbents, natural weathering at the first stage, followed by phytomelioration. The duration of soil restoration is at least 4-5 years.

Tundra-gley soils of the forest-tundra region. Oil biodegradation processes occur at a very low speed. Self-purification of soils occurs mainly due to mechanical dispersion. Effective ways reclamation is unclear.