Urban soils are anthropogenically modified soils that have the resulting human activity a surface layer more than 50 cm thick, obtained by mixing, pouring or burying material of urban origin, including construction and household waste.
General features of urban soils are:
- parent rock - bulk, alluvial or mixed soils or cultural layer;
- inclusion of construction and household waste in the upper horizons;
- neutral or alkaline reaction (even in a forest area);
- high contamination with heavy metals (HM) and petroleum products;
- special physical and mechanical properties of soils (reduced moisture capacity, increased bulk density, compaction, rockiness);
- upward profile growth due to the constant introduction of various materials and intense aeolian sputtering.
The specificity of urban soils lies in the combination of the listed properties. Urban soils are characterized by a specific diagnostic horizon "urbic" (from the word urbanus - city). The “urbic” horizon is a surface organic-mineral bulk, mixed horizon, with urban-anthropogenic inclusions (more than 5% of construction and household waste, industrial waste), more than 5 cm thick (Fedorets, Medvedeva, 2009).
As a result of anthropogenic impact, urban soils have significant differences from natural soils, the main of which are the following:
- formation of soils on bulk, alluvial, mixed soils and cultural layer;
- presence of inclusions of construction and household waste in the upper horizons;
- changes in acid-base balance with a tendency towards alkalization;
- high contamination with heavy metals, petroleum products, components of emissions from industrial enterprises;
- changes in the physical and mechanical properties of soils (reduced moisture capacity, increased density, rockiness, etc.);
- profile growth due to intensive spraying.
Some groups of urban soils can be distinguished: natural undisturbed, preserving the normal occurrence of natural soil horizons (soils of urban forests and forest parks); natural-anthropogenic surface transformed, the soil profile of which is changed in a layer less than 50 cm thick; anthropogenic deeply transformed soils formed on the cultural layer or bulk, alluvial and mixed soils with a thickness of more than 50 cm, in which physical and mechanical restructuring of profiles or chemical transformation has occurred due to chemical pollution; urban-technozems are artificial soils created by enriching with a fertile layer, peat-compost mixture of bulk or other fresh soils. In the city of Yoshkar-Ola, in the Zarechnaya part of the city, an entire microdistrict was built on artificial soil - sand that was washed up from the bottom of the river. Malaya Kokshaga, soil thickness reaches 6 m.
Soils in the city exist under the influence of the same soil-forming factors as natural undisturbed soils, but in cities, anthropogenic soil-forming factors prevail over natural factors. The features of soil-forming processes in urban areas are as follows: soil disturbance as a result of the movement of horizons from natural locations, deformation of the soil structure and the order of arrangement of soil horizons; low content organic matter- the main structure-forming component of the soil; a decrease in the population size and activity of soil microorganisms and invertebrates as a result of a deficiency of organic matter.
Significant harm to urban biogeocenoses is caused by the removal and burning of leaves, as a result of which the biogeochemical cycle of soil nutrients is disrupted; The soils are constantly becoming poorer, and the condition of the vegetation growing on them is deteriorating. In addition, burning leaves in the city leads to additional pollution of the city atmosphere, since it releases the same harmful pollutants into the air, including heavy metals that were sorbed by the leaves.
The main sources of soil pollution are household waste, automobile and railway transport, emissions from thermal power plants, industrial enterprises, wastewater, construction waste.
Urban soils are complex and rapidly developing natural-anthropogenic formations. The ecological state of the soil cover is influenced by negative impact production facilities through emissions of pollutants into the air and due to the accumulation and storage of production waste, as well as emissions from motor vehicles.
The result of many years of exposure to polluted atmospheric air is the content of metals in the surface layer of urban soils associated with changes technological process, the efficiency of dust and gas collection, the influence of metrological and other factors.
As the results of a number of studies have shown (Voskresenskaya, 2009), the content heavy metals- lead, cadmium, copper and zinc are unevenly distributed throughout the city of Yoshkar-Ola (Table 5-6). Analyzing the research data, it should be noted that the concentration of heavy metals in the city as a whole does not have a clearly defined direction, but rather has a mosaic distribution.
Table 5 - Content of heavy metals in the soil of the city of Yoshkar-Ola
(Voskresenskaya, 2009)
| № | Study area, streets | Content of heavy metals, mg/kg |
|||
| lead | cadmium | copper | zinc | ||
| Forest park area |
|||||
| 1 | SPNA "Pine Grove" | 4.2±0.01 | 0.9±0.01 | 2.2±0.01 | 21.5±0.03 |
| Industrial and residential zones |
|||||
| 2 | Krasnoarmeyskaya | 146.5±8.46 | 1.6±0.06 | 45.6±2.63 | 169.6±9.79 |
| 3 | Soviet | 28.1±1.33 | 1.2±0.01 | 22.7±1.08 | 173.7±8.87 |
| 4 | Lunacharsky | 47.0±2.13 | 0 | 20.8±1.09 | 141.3±7.58 |
| 5 | Mechanical engineers | 35.0±0.05 | 0.5±0.01 | 104.9±0.96 | 37.5±0.01 |
| 6 | Warriors of internationalists | 22.5±0.02 | 0.7±0.01 | 37.5±0.31 | 96.7±0.02 |
| 7 | Tap | 27.5±0.01 | 0.5±0.03 | 25.0±0.03 | 13.8±0.01 |
| 8 | Pushkin | 34.2±0.02 | 2.0±0.01 | 35.2±0.03 | 12.7±0.01 |
| 9 | Panfilova | 25.0±0.02 | 0 | 86.5±0.05 | 33.8±0.01 |
| 10 | Karl Marx | 30.7±0.02 | 0 | 21.0±0.06 | 82.2±3.02 |
| 11 | Leninsky Prospekt | 51.7±0.01 | 0.5±0.01 | 82.7±0.02 | 112.5±8.42 |
| 12 | Kirov | 40.0±0.03 | 0 | 25.5±0.03 | 38.2±0.03 |
| 13 | Dimitrova | 29.2±0.03 | 0.9±0.02 | 25.5±0.06 | 33.7±0.01 |
| 14 | Communist | 32.4±0.03 | 0 | 21.7±0.03 | 98.0±7.01 |
| 15 | Eshkinina | 36.7±0.03 | 0 | 35.2±0.03 | 94.2±0.51 |
| 16 | Eshpaya | 34.2±0.04 | 0 | 38.0±0.06 | 92.3±3.01 |
| 17 | IvanaKyrli | 93.5±0.04 | 0 | 92.5±0.05 | 232.5±7.02 |
| 18 | Karl Liebknecht | 51.4±0.09 | 0.4±0.01 | 38.3±0.12 | 72.3±1.12 |
| Average content for the city, excluding protected areas | 48,5 | 0,5 | 42,3 | 96,2 | |
| MPC (gross content) | 130,0 | 2,0 | 132,0 | 220,0 | |
Table 6 - Values of the complex soil pollution index, Zc
(Voskresenskaya, 2009)
| № | Study area | Zc | Pollution level assessment |
| 1 | Krasnoarmeyskaya | 24,97 | moderately dangerous |
| 2 | Soviet | 13,62 | acceptable |
| 3 | Lunacharsky | 11,51 | acceptable |
| 4 | Mechanical engineers | 34,94 | dangerous |
| 5 | Warriors of internationalists | 24,79 | moderately dangerous |
| 6 | Tap | 7,03 | acceptable |
| 7 | Pushkin | 11,37 | acceptable |
| 8 | Panfilova | 28,08 | moderately dangerous |
| 9 | Karl Marx | 8,54 | acceptable |
| 10 | Leninsky Prospekt | 31,34 | moderately dangerous |
| 11 | Kirov | 8,41 | acceptable |
| 12 | Dimitrova | 8,36 | acceptable |
| 13 | Communist | 9,52 | acceptable |
| 14 | Eshkinina | 13,99 | acceptable |
| 15 | Eshpaya | 4,75 | acceptable |
| 16 | J. Kirli | 22,79 | moderately dangerous |
| 17 | K. Liebnecht | 44,31 | dangerous |
| 18 | Park of the XXX anniversary of the Komsomol | 4,92 | acceptable |
| 19 | Plant NP "Iskozh" | 12,37 | acceptable |
| 20 | OJSC "Marbiopharm" | 22,47 | moderately dangerous |
| 21 | CJSC "Meat Processing Plant" | 5,47 | acceptable |
| 22 | OKTB "Crystal" | 11,47 | acceptable |
| 23 | OJSC "MMZ" | 21,13 | moderately dangerous |
Despite the heterogeneity of urban soils, the results obtained make it possible to identify the degree of anthropogenic influence on the content of metals in the soils of the city of Yoshkar-Ola. The analysis showed that in the city’s soil the lead content is 11.5, copper is 19.2, and zinc is 4.5 times higher than in the Sosnovaya Roshcha forest park. In general, it should be noted that in the studied soils of the city of Yoshkar-Ola, no significant excesses of the maximum permissible concentration for the gross content of heavy metals were revealed, however, there is still enough high level maintenance of TM along highways and in the industrial part of the city.
When studying the contamination of urban soils with radionuclides (Voskresensky, 2008), it was found that higher contents of 40K, 226Ra, 232Th and 90Sr were observed in anthropogenically contaminated areas, this is explained by the fact that in the city of Yoshkar-Ola up to 30% of the territory is occupied by soils with strong the degree of disturbance of the profile, the structure of which contains bulk humus layers with a thickness of 18 to 30 cm, as well as buried organomineral (sometimes peat) horizons. It is known that the levels of radionuclides in soils are largely determined by their content in soil-forming rocks. In general, the content of radionuclides in the soils of the city of Yoshkar-Ola can be classified as insignificant; a higher level of contamination of urban soils with radioactive elements is associated with anthropogenic activities. In general, soil contamination with the main dose-forming radionuclides does not cause concern; the average value for the city of Yoshkar-Ola is much lower than for Russia (State report ..., 2007, 2008, 2009).
Thus, the soils of Yoshkar-Ola have a low level of pollution, which indicates that despite the high anthropogenic load, urban soils have retained the ability to self-purify. In addition, soil contamination with heavy metal salts is not actual problem, since on the territory of the city there are no chemical, metallurgical, petrochemical and other enterprises that are sources of air and soil pollution.
Soil directly affects the habitat and quality of life of the population. Therefore, the problems of collection, storage, removal and disposal of production and consumption waste, improvement and sanitary maintenance populated areas continue to be one of priority areas in ensuring the sanitary and epidemiological well-being of people.
Waste disposal. Waste refers to the remains of raw materials and semi-finished products generated during the manufacturing process and which have lost, in whole or in part, the consumer properties of the original material; products of physical and chemical processing of raw materials, as well as the extraction and enrichment of minerals, the production of which is not the purpose of the production process in question and which can be used in production as raw materials for processing, fuel, etc. Waste refers to material objects that may have high potential danger to the environment and public health.
Waste is divided into household (municipal) and industrial (production waste). In turn, household and industrial waste can be divided into two groups: solid (waste of metals, wood, plastics, dust, garbage, etc.) and liquid (sediment waste water, sludge, etc.). Waste according to the degree of possible harmful effects on environment are divided into extremely dangerous (class 1), highly dangerous (class 2), moderately dangerous (class 3), slightly dangerous (class 4) and practically non-hazardous (class 5). Waste hazard classes were introduced by Federal Law No. 309-FZ of December 30, 2008.
The amount of accumulated garbage on the planet is growing, with each city resident producing from 150 to 600 kg of garbage per year. Per citizen Russian Federation there are 300-400 kg/year of household waste (in Moscow - 300-320 kg).
The main unresolved issues in the field of sanitary cleaning of populated areas are: the presence of unauthorized landfills, leading to contamination of soil, groundwater, atmospheric air and being a food source for mouse-like rodents; increased accumulation of waste, changes in its structure, including those with a long decomposition period; unsatisfactory organization of waste collection, storage and removal. Such problems are most typical for the city of Yoshkar-Ola. Garbage collection sites, built mainly 30-40 years ago to accumulate up to 1 m3 of waste per inhabitant, are now used at a rate of 1.25 m3. In fact, taking into account large-sized waste, including complex combined composition in the form of products that have lost their consumer properties (old furniture, household appliances, household appliances, strollers, packaging, home renovation waste, etc.), this norm exceeds 1.45 m3, and in the central part of the city it is about 2 m3. The opening of a significant number of new organizations of small retail trade, public catering, public service facilities, and office premises continues to aggravate the problem (Annual Report..., 2010).
Currently, there are several ways to dispose of waste. According to the technological essence, waste disposal methods can be divided into: 1) biothermal (landfills, plowing fields, storage areas, compost fields and a biothermal composting plant); 2) thermal (combustion without use, combustion of waste as energy fuel, pyrolysis to produce flammable gas and petroleum-like oils); 3) chemical (hydrolysis); 4) mechanical (pressing waste into building blocks). But the most widespread are biothermal and thermal methods. In Russia, the waste sorting system at landfills is poorly organized.
An analysis of the fractional composition of municipal solid waste (MSW) arriving at the municipal solid waste landfill in the city of Yoshkar-Ola showed that food waste accounts for 40-42%, paper - 31-33, wood - 4.6-5.0, polymer materials- 3.5-5.0, textiles - 3.5-4.5, cullet - 2.0-2.5, stones and ceramics - 1.5-2.0, ferrous and non-ferrous metals - 0.5- 0.6, bones - 0.3-0.5, leather and rubber - 0.5-1.0, coal and slag - 0.8-1.5 and dropouts - 11.0-20.0% (table .7).
Table 7 - Composition of solid household waste in the Russian Federation and the city of Yoshkar-Ola, %
(Ecology of the city of Yoshkar-Ola, 2007)
Waste disposal sites. A waste disposal site is a special engineering structure that eliminates the negative impact on the environment during waste disposal. The project for organizing and constructing a landfill involves the creation of impervious multilayer screens that prevent the flow of filtrate into soils and aquifers. Along with this, leachate is collected and purified at the landfill. The organization and construction of the landfill is carried out in accordance with the legislation in the field of environmental protection and waste management, sanitary-epidemiological and urban planning legislation, as well as in the presence of a positive conclusion of the state examination for the construction project.
A modern solid waste landfill is a complex of environmental structures designed for the centralized collection, neutralization and burial of solid waste, preventing the release of harmful substances into the environment, pollution of the atmosphere, soil, surface and groundwater, the spread of rodents, insects and pathogens.
In the urban district "City of Yoshkar-Ola" there are two waste disposal facilities: one for the disposal of solid household waste, and the second for industrial waste. A solid waste landfill is intended for storing solid waste and provides for constant, albeit very long-term waste processing with the participation of air oxygen and microorganisms.
Industrial waste of hazard class 3-4 (sludge containing salts of heavy metals, acids, alkalis, etc.) generated during production at industrial enterprises of the city is accepted at the industrial waste landfill in Yoshkar-Ola.
According to the Federal Law of 08.08.2001 No. 128-FZ, activities for the collection, use, neutralization, transportation, and disposal of waste of hazard class I - IV are subject to licensing. Activities for the accumulation of waste of hazard class I - V, as well as activities for the collection, use, neutralization, transportation, and disposal of waste of hazard class V (as amended) are not subject to licensing. Federal Law dated December 30, 2008 N 309-FZ).
The soils and soil cover of the Far East are characterized by great variety, which is determined by the bioclimatic heterogeneity of the conditions of their formation from the arctic desert zone in the north to the forest-steppe zone in the south and from the humid ocean coast in the east to continental spaces in the west.
The history of studying soils in the Far East goes back more than a hundred years, but modern performance about soils, soil-forming processes, and the uniqueness of regional soil formation has been developed over the last 50 years. It is reflected in individual publications and monographs of a number of authors. The knowledge of soils and soil cover of various subregions of the Far East is far from ambiguous. The most studied are the soils of the south of the Far East, which is associated with its more active, although not earlier, development.
The unique nature of the southern half of the Far East and its soils are described in the work of Yu.A. Liverovsky, B.P. Kolesnikova (1949). In special monographic works by G.I. Ivanova (1964, 1966, 1976) most fully covered the issues of genesis and classification of soils in Primorye. A certain contribution to the study of soils of coniferous-deciduous and broad-leaved forests in the low mountains of Primorye was made by N.A. Kreydoy (1970), and soils of mountain dark coniferous forests - N.F. Pshenichnikova (1989). In the last decade, works have appeared that expand the understanding of the specifics of soil formation within mountainous (Pshenichnikov, Pshenichnikova, 2002) and lowland territories (Shlyakhov, Kostenkov, 2000) continental-oceanic ecosystems, as well as floodplain soils of south-eastern Primorye (Shelest, 2001).
Soil characteristics Khabarovsk Territory and the Amur region is most fully reflected in the work of A.T. Terentyev (1969), and later in the monographs of employees of the Khabarovsk Scientific Research Institute Yu.S. Prozorova (1974), Yu.I. Ershova (1984), A.F. Makhinova (1989).
The soils of the island ecosystems of Sakhalin and the Kuril Islands are comprehensively presented in two monographs by A.M. Ivleva (1965, 1977).
The soils of the Kamchatka Peninsula have been studied to a much lesser extent. The work of I. A. Sokolov (1973) is still the single most complete source on the relationship between volcanism and soil formation in the Far East.
The territory of the Magadan region is characterized by the least development and, as a result, its soils are the least studied. E.M. Naumov, B.P. Gradusov (1974) was one of the first to summarize the material on the characteristics of taiga soil formation in the Far Northeast of Eurasia. Somewhat later, employees of the institute Biological Problems The North Far Eastern Scientific Center of the USSR Academy of Sciences publishes the work “Geography and Genesis of Soils in the Magadan Region”, edited by V. I. Ignatenko (1980).
To date, questions of the genesis and classification of soils in individual parts of the Far East have been developed with varying degrees of detail. It is advisable to generalize and generalize the available material on soils of the entire Far East. Such an attempt was made by B.F. Pshenichnikov (1986) within the framework of the textbook “Soils of the Far East”.
In the present textbook the formation conditions, morphological structure of soils, soil formation processes, classification and zoning of soils in the Far Eastern region are considered, which, we hope, will help novice researchers develop an idea of the soils of the Far East.
Let's first briefly look at theoretical issues classification of soils and soil-geographical zoning.
V.V. Dokuchaev first gave scientific definition soil as an independent natural-historical body of nature (the same as plants, animals, etc.), formed as a result of the simultaneous interaction of soil-forming factors: climate, rock, vegetation and fauna, relief and age. A certain combination of soil-forming factors leads to the formation of a genetic soil type, accepted by V.V. Dokuchaev as the main classification unit.
According to the classification of soils in force in Russia (Classification and diagnostics of soils of the USSR, 1977), the main taxonomic unit - the genetic type of soils - combines soils with a single profile structure, formed as a result of the development of the same type of soil formation process in conditions with a similar water-thermal regime, on parent rocks of similar composition and under homogeneous vegetation.
Several dozen soil types have been identified on the territory of Russia. Some of them are widespread, for example, chernozems, podzolic soils, and brown forest soils. The latter are zonal soils of the south of the Far East.
Each genetic soil type is successively subdivided into subtypes, genera, species, varieties and categories.
A soil subtype is a transitional group of soils between types that differ in the manifestation of the main and accompanying processes of soil formation. For example, when the podzolization process develops in the soil along with brown soil formation, a subtype of brown forest podzolized soils is formed; the development of the soddy process along with the podzolic one leads to the formation of a subtype of soddy-podzolic soil. The appearance of a subtype may also be due to significant dynamics of the main characteristic of the type (for example: light gray, gray, dark gray forest soils) or facial features of natural conditions within the soil zone (for example, southern chernozem).
The soil genus is distinguished within subtypes and is represented by a group of soils, the qualitative genetic characteristics of which are determined by the composition of the soil absorption complex and salinity chemistry, determined by a number of local conditions: the composition of soil-forming rocks, the chemistry of groundwater, relict characteristics of the soil-forming substrate.
A soil type is a group of soils within a genus, differing in the degree of development of the main soil-forming process. For example, according to the degree of podzolization (weak, medium, strongly podzolized), humus content (medium, highly humified).
Soil variety - a group of soils within a genus, differing in the granulometric composition of the upper horizons (for example, clayey, loamy, etc.).
Soil discharges are a group of soils of the same type and the same mechanical composition, but developed on parent rocks of different origins and different petrographic composition (for example, on granites, limestones, alluvium).
In order to determine the type of soil, it is necessary first of all to determine the type of soil profile based on studying it morphological structure. How to do this is described in detail in our methodological manual for the first environmental practice (Urusov et al., 2002). Then it is necessary to compare the morphological indicators with the diagram of the morphological structure of various soils. Having determined the type of soil profile, it is necessary to determine the type of geographic landscape, the geographic area of the given soil, the main and accompanying elementary soil-forming processes, the type of migration and accumulation of substances in the given soil.
When diagnosing soils, first of all, data on the morphological structure of the profile, soil formation conditions, data on the content and nature of intra-profile differentiation of humus, the composition of absorbed bases, as well as intra-profile differentiation of physical clay and sand, silt and gross chemical composition are used.
Soil-geographical zoning is the identification of territories that are homogeneous in soil cover structure, similar in soil formation conditions and in their possible use in agricultural production.
In 1962, at Moscow State University (Soil-geographical zoning of the USSR, 1962), a soil-geographical zoning scheme was developed, which is presented below.
Taxonomic system of soil-geographical zoning:
A soil bioclimatic zone is a set of soil zones and vertical soil structures that are similar in radiation and thermal conditions and the nature of their influence on the development of vegetation, weathering and soil formation. The determining indicator when identifying a belt is thermal conditions.
Soil-bioclimatic region This is an area of soil zones and vertical soil structures within the soil-bioclimatic zone, distinguished by the uniqueness of moisture and continentality, and as a consequence of this - specific features development of vegetation, weathering and soil formation. Diagnostic indicators for identifying an area are the conditions of moisture and continentality.
Vertical soil structure is the area of a certain number of vertical soil zones, determined by the position of a mountainous country in the system of soil-bioclimatic regions and the main features of the general orography. In terms of its taxonomic position in the zoning system, the vertical soil structure is identical to the soil zone on the plain. The leading indicators when identifying vertical soil structures are thermal conditions, moisture and the type of soil formation in the lower zone. Soil province is a part of the soil zone, distinguished by the uniqueness of its moisture and continentality, temperature differences that determine the specificity of soils and soil formation conditions. The vertical soil zone is the area of a certain zonal mountain type of soil.
Soil district is part of a province or vertical soil zone with a certain genetic type of relief, within which a certain combination of soils and soil-forming rocks can be traced. The significant differences between the districts are due to the characteristics of the local climate and vegetation cover. A soil region is an area of soils within a soil district with a relatively uniform topography, the composition of the soil and vegetation cover and a certain microrelief.
Specifics geographical location The Far East of Russia (Fig. 2), which crosses three soil-bioclimatic zones from north to south: polar (cold), boreal (moderately cold), subboreal (temperate), determines a wide variety of soil formation conditions and the identification within them of the following soil regions, zones and provincial
1http://www.priroda.ru/regions/info/detail.php?SECTION_ID=&FO_ID=440&ID=6452
2http://xn--80aa2bkafhg.xn--p1ai/article.php?nid=12709
3http://www.kmslib.ru/kraevedenie/geografiya
4http://ecology-of.ru/priroda/klimat-goroda-khabarovsk
5 https://abc.vvsu.ru/books/u_ekologija/page0002.asp
6 http://samanka.ru/osobennosti-landshaftnogo-dizajna.html
The soil cover of the urban area is represented by natural soils of varying degrees of disturbance and soils of anthropogenic origin (soils or, as they are now commonly called, urbanozems). The bulk of the soil in the city is under a layer of asphalt, under houses and under lawns. Natural soils can only be found in areas of natural forests located within the city.
The system of horizons in urban soils, their thickness, and morphological expression in different areas of the urban area vary greatly. There is a complete disappearance of some horizons (A 1, A 1 A 2, A 2 B) or a violation of their sequence, the appearance of bleaching and gleying at the contact of layers of different granulometric compositions. In the steppe zone, urban soils lack horizons A, AB, and often horizon B1; inclusions of garbage, brick fragments, etc. are found.
Soils of varying degrees of disturbance are usually confined to peripheral areas and residential areas. These soils combine an undisturbed lower part of the profile and anthropogenically disturbed upper layers. According to the method of formation, the top layer can be bulk, mixed or mixed-bulk. The disturbance may affect the humus-accumulative horizon, or may reach illuvial horizons. Thus, the profile of sod-podzolic slightly disturbed soil has the following structure: U↓ (0...25 cm) - an urbanized layer formed as a result of mixing soil layers, dark gray, with inclusions of bricks and household waste; followed by the horizons: A 2 B, B 1, B 2 and C.
The profile of sod-podzolic highly disturbed soil includes the following horizons: U 1h (0...15 cm) - an urbanized humus layer of dark gray or gray color with inclusions; U 2h ↓ (15...50 cm) - an urbanized layer with humus running along the roots, gray or light gray in color, contains an abundance of inclusions of a domestic or industrial nature; gradually passes into the B 1 horizon, then into the B 2 and C horizons.
Most urban soils are characterized by the absence of genetic soil horizons A and B. The soil profile is a combination of anthropogenic layers of different color and thickness with inclusions of household, construction, and industrial waste (U 1, U 2, U 3, etc.). Such soils, or urban soils, are typical for the central part of cities and areas of new buildings.
The soils of lawns and squares have a unique soil profile. It is distinguished by the large thickness of the humus horizon and humus-peat-compost layer (70...80 cm or more), which develops in the lower illuvial part of the soil profile.
Compared to natural conditions In the city, all soil formation factors change, the main one of which is human activity.
The thermal regime of soils changes greatly. The soil temperature on the surface is on average 1...3 °C (10 °C) higher than the surrounding area. This is more common on highways and in high-density areas. The soil is heated from within by the city heating network. In this regard, the snow melts early and the growing season of plants increases.
The presence in the city of significant waterproof areas with reduced infiltration capacity causes a significant change in the drainage process. This manifests itself in a decrease in time, an increase in the volume and intensity of runoff, which leads to increased erosion processes, as well as soil washout. As a result of such unfavorable phenomena, there is a decrease in moisture reserves in the root layer.
In cities, there is a leveling of landforms: filling up ravines, cutting off hills and slopes.
Characteristic feature urban soils is the absence of litter, and where it is present, its thickness is very small (no more than 2 cm). The granulometric composition of soils and soils is predominantly light loamy, less often sandy loam and medium loamy. The admixture of skeletal material in anthropogenically disturbed soils reaches 40...50% or more. The soil contains inclusions of a domestic nature. Due to the high recreational load, strong compaction of the soil surface is observed. The bulk density is generally 1.4...1.6 g/cm 3 , and in residential areas - up to 1.7 g/cm 3 .
Distinctive feature urban soils - high pH value. Exchangeable acidity averages 4.7...7.6, which is significantly higher than in the soils of nearby areas (3.5...4.5).
It should be noted that the formation of soil cover occurs with the active replacement of soil-forming rocks, fragmentation of the structure due to partial sealing with artificial coverings, depreciation or degradation, up to the complete replacement of soils in certain areas.
A special place among the manifestations of anthropogenic impact on the soils of megacities belongs to the pollution of urban areas with heavy metals, since rapid self-purification of soils from metal pollution to the required level for reasons of hygienic and environmental safety is difficult and in many cases practically impossible.
The main sources of heavy metals in the city are: the transport and road complex, industrial enterprises, unutilized industrial and municipal waste.
Total soil contamination with chemical elements
Zinc, lead, copper, and mercury are widely distributed and actively accumulate in soils. Mainly at background concentrations they contain molybdenum, nickel, tin, barium, chromium, cadmium, beryllium, cobalt and boron.
A study of the soil cover showed that about 43% of the city's area falls into the category of weak (acceptable) pollution (Zc less than 16). Soils with an average (moderately dangerous) level of pollution (Zc 16-32) occupy 28% of the entire territory. On 27% of the area, severe (dangerous) soil contamination was detected (Zc 32-128), and on 2% the maximum (extremely dangerous) level was recorded (Zc more than 128).
Soils with acceptable levels of contamination are distributed mainly on the periphery of Moscow, mainly in the west and southwest, and are confined to large urban forest parks. Such soils are found fragmentarily in the north, south and east of the city ().
Heavily contaminated soils extend in a wide strip from northwest to southeast, covering central part cities.
Foci of maximum soil contamination have been identified mainly in the area of industrial zones or are located in their zone of influence. Most of these outbreaks were recorded in the Central, South-Eastern, Southern and Eastern districts.
Lowest concentration chemical elements in the soils of Western administrative district.
Depending on the functional purpose of the territories, the level of chemical elements in soils decreases in the following order: industrial zones (Zc 45) - squares, boulevards, residential areas (Zc 31) - cultural and recreation parks (Zc 28) - wastelands (Zc 21) - natural and national parks (Zc 12-13).
The soils of industrial zones are subject to the most powerful technogenic pressure; here, even the average value of the pollution index (Zc) corresponds to a dangerous level of pollution. The soils of public gardens, boulevards and residential areas are also approaching dangerous levels of pollution. Squares and boulevards are usually located near highways and are exposed to vehicle emissions. The main sources of soil pollution in residential areas are municipal waste and vehicles.
Soil contamination with individual chemical elements
The main soil pollutants in the city are zinc, lead, copper, cadmium, tin, molybdenum and chromium.
Below is brief description distribution of widespread and most toxic chemical elements in soils in the city.
Mercury
The established concentrations of mercury in soils in Moscow range from 0.02 to 2.1 mg/kg, with an average content of 0.2 mg/kg. Increased concentrations of the metal are typical for the Central and South-Eastern districts of the capital.
In general, mercury contamination of city soils is insignificant and does not pose an environmental hazard.
Cadmium
Concentrations of this element in soils of the city of Moscow vary widely with an average value of 0.3 mg/kg, which is significantly lower than the established MPC (2 mg/kg).
The highest concentrations of the element are characteristic of the South-Eastern, Southern and Central districts.
Contamination of soils in the city of Moscow with cadmium is manifested to a greater extent than mercury pollution, but in general it is assessed as low.
Lead
Widely distributed in the city's soil cover, its average content is 96.5 mg/kg. The distribution of lead in the city is shown in Fig. 6.5.2.
On approximately 20% of the city's area, the concentration of lead in the soil exceeds the MEC value (130 mg/kg), and on 5% of the territory the concentration of the element exceeds the MAC by more than 2 times. Soils with lead concentrations less than the maximum concentration limit are distributed mainly on the periphery of the city. The soils of the Central Administrative District are most contaminated, and the least contaminated are those of the Western and Southwestern districts.
In comparison with the monitoring results of 2006, there was an increase in the lead content in Moscow soils, which is undoubtedly due to the constantly increasing number of vehicles in the city and the continued use of gasoline with lead additives.
Zinc
The most contaminated soil is in the districts of the Central Administrative District, North-Eastern Administrative District, Southern Administrative District, South-Eastern Administrative District and Eastern Administrative District, where contaminated soil with contents close to the UEC occupies about 70-80% of the area. The least contaminated soil is the western sector of the city - the districts of the North-Western Administrative District, the Western Administrative District, and the South-Western Administrative District ().
Soils with zinc concentrations less than 0.5 TAC in surface horizons are distributed mainly on the periphery of the city, but relatively small areas of soils relatively uncontaminated with zinc are found throughout its territory.
Copper
On 91.5% of the city's area, the copper content is below the APC value (less than 132 mg/kg). At the same time, in the territory of ZAO and SZAO, and in other districts in the strip from the district railway up to the city limits, the copper content usually does not reach 0.5 ODC. In the central part of the city, concentrations ranging from 0.5 to 1 TAC value predominate. On 7.5% of the city's territory the copper content is at the level of 1-2 OPC, only on 1.4% of the territory it is 2-4 OPC and on 0.6% of the area it is above 4 OPC values.
Chromium
The average chromium content in the city's soils is about 58 mg/kg. The average concentrations of the element in the soils of administrative districts differ slightly and do not exceed the maximum permissible contents (MPC 90 mg/kg). The highest concentrations of chromium were found in the soils of the southern sector of the city; the least contaminated soil was in the Western and Northwestern districts.
On 7.5% of the city's territory, chromium content exceeds the maximum permissible concentrations in soils (MPC) up to 2 times and only on 1.2% of the surveyed area they exceed 2 MAC.
Nickel
The results of the study allow us to assess the contamination of urban soils with nickel as insignificant and not posing a significant environmental hazard.
Manganese
Elevated contents of this element were detected in the territories national park Elk Island and Bitsa Natural Park. Contents close to the background analogue were recorded in the Tsaritsyno, Troparevsky, Filevsky parks, and in the Serebryanoborsky forestry. In the rest of the city, the manganese content in soils is generally below the background value.
Thus, the analysis of the content of heavy metals in the city’s soils showed that, according to the total pollution indicator (Zc value), the existing technogenic pollution of the city’s soil cover on 43% of the territory is characterized by a low level and a satisfactory environmental situation. Recorded on 28% of the area intermediate level pollution and 29% - high and maximum levels of pollution, which makes it possible to classify them as territories with increased risk for the health of the population living here.
In urban conditions, the most obvious combination of natural soil-forming factors with newly emerged, more powerful and, undoubtedly, dominant anthropogenic factors is observed, which leads to the formation of specific soils and soil-like bodies here. And today it has become obvious that soil is not always an object of potential fertility that gives life; in the conditions of modern technogenesis, it acts to a greater extent as a natural body, preserving, due to the high potential of its protective functions, the ecological balance of a particular landscape. And urban soils are a clear example of this.
The main result of the development of the urbanization process is the significant alienation of productive land for development and industrial facilities, while the area of such land is increasing everywhere. The main reason for the transformation of the soil cover of cities lies in the ever-progressing construction activity of mankind. This is associated with soil changes, including the removal, destruction or movement of the fertile layer, as well as the accumulation, possibly, of harmful industrial and construction waste. There are especially many such lands in Europe. According to M.N. Stroganova (1997), in Belgium they occupy 28%, Great Britain - 12%, Germany - 11% of the area. In the Russian Federation in cities and populated areas, on an area equal to 0.65% of total area, lives about 3/4 of the population, i.e. more than 100 million people.
It should be noted that the increased intensity of anthropogenic transformation of soils over recent decades has led to a significant change in the component composition and structure of the soil cover of large areas. All soils of the city are divided into groups: natural undisturbed soils, natural-anthropogenic superficially transformed soils, anthropogenic deeply transformed urbanozems and soils of technogenic surface soil-like formations - urbantechnozems.
The main difference between urban soils and natural soils is the presence of a diagnostic horizon "urbic". This is a surface bulk, mixed horizon, part of a cultural layer more than 50 cm thick, with an admixture of more than 5% of anthropogenic inclusions (construction and household waste, industrial waste). Its upper part is humused. There is an upward growth of the horizon due to atmospheric dust fallout, aeolian movements, and anthropogenic activity. Natural undisturbed soils retain the normal occurrence of natural soil horizons and are confined to urban forests and forested areas located within the city.
Naturally anthropogenic surface transformed soils in the city are subject to a surface change in the soil profile of less than 50 cm in thickness. They combine the horizon " urbic" less than 50 cm thick and an undisturbed lower part of the profile. Soils retain a type name indicating the nature of disturbance (for example , urbo-podzolic scalped, buried, etc.).
Anthropogenic deeply transformed soils form a group of urban soils proper urbanozems, in which the horizon urbic has a thickness of more than 50 cm. They are formed due to urbanization processes on the cultural layer or on bulk, alluvial and mixed soils with a thickness of more than 50 cm, and are divided into 2 groups: physically transformed soils, in which a physical and mechanical restructuring of the profile has occurred ( urbanozem, kulturozem, necrozem, ekranozem); chemically transformed soils in which significant chemogenic changes in the properties and structure of the profile have occurred due to intense chemical pollution by both air and liquid, which is reflected in their separation (industrizem, intruzem).
In addition, soil-like technogenic surface formations are formed on the territory of cities - urban technozems. They are artificially created by enriching bulk or other fresh soils with a fertile layer or peat-compost mixture. Among them are replantozems, constructozems.
There is no doubt that the natural soil cover in most of modern cities has been destroyed and (or) is undergoing dramatic changes, therefore, along with the study of the influence of urban soil pollution on the ecology of the city, interest in the features of their morphology and physical and chemical structure is increasing. Significant differences between these soils and natural soils were noted (Table 1).
Table 1 - Signs of newly emerged urban soils
