Theoretical Assignments

Soil is a surface layer of lithosphere (from few millimeters in mountains and up to 10 kilometers in lowlands), which was formed after beginnings of life on Earth as the result of climate, flora and life (microorganisms and roots of higher plants) influence. Soil consists of the surface or fertile layer (0-25 cm) or humus layer, which is characterized by fertility and which is cultivated at growing plants, and of soil itself.

Soils are very different depending on conditions of their formation, first of all on climate and flora. In Ukraine most common are chernozem (black earth soils) (54.0% of territory), then –– grey forest soils (18.2% of territory).

Soil consists of biotic (soil microorganisms) and abiotic components. Abiotic components include hard substance of soil (mineral and organic compounds and organomineral complexes), soil moisture and soil air.

60––80% of mineral (non-organic) substances of soil are represented by crystalline silica or quartz. The important place among mineral compounds is occupied by alumina-silicates, i.e. feldspar and mica.

Organic substances of soil are represented both by soil organic (humic acids, fulvic acids etc.) compounds, which are created by soil microorganisms and which are called humus, and by strange for soil organic substances, which came into the soil from outside in the result of natural processes and technogenic (anthropogenic) pollution.

Basic components of the soil and its hygienic significance:

- air permeability – soil ability to let air through its thickness. It increases when size of pores is bigger and doesn’t depend on their total volume (porosity);

- water permeability – soil ability to absorb surface water and to let it pass through. Permeability consists of two stages: imbibition, when free pores gradually get filled with water till total saturation of soil and filtration, when, in the result of total water saturation of soil, water starts moving in soil pores because of gravity;

- moisture capacity – amount of moisture, which soil is capable to retain due to sorptive and capillar powers. The smaller is the size of pores and the bigger is their total volume, i. e. porosity – the bigger is the moisture capacity. The finer is soil texture, the higher is its moisture capacity;

- soil capillarity – soil ability to lift water via capillaries from the bottom layers up. The smaller is the size of soil texture particles - the bigger is soil capillarity, but in such soil water goes up higher and slower.

Soil capability to transform organic compounds into mineral substances good for plants’ assimilation: carbohydrates – into water and carbon dioxide; fats– into glycerin and fatty acids and then – also into water and carbon dioxide; proteins – into amino acids with ammonia and ammonia salts evolvement and their further oxidation to nitrites and nitrates; protein sulfur – into hydrogen sulfide etc.

Migration takes place both in short (soil –– plant –– soil, soil –– water –– soil, soil –– air –– soil) and long (soil –– plant –– animal –– soil, soil –– water –– plant –– soil, soil –– water –– plant –– animal –– soil, soil –– air –– water –– plant –– animal –– soil etc.) migration chains;

- forms the chemical structure of foodstuffs of vegetable and animal origin;

- plays an important role in formation of water quality of surface and ground sources of domestic and drinking water-supply;

- affects qualitative structure of contemporary atmosphere;

- of endemic importance – anomalous natural chemical structure of soil in endemic provinces is a reason of rise and local spreading of endemic diseases (geochemical endemic diseases): endemic fluorosis and caries, endemic goiter, foot-and-mouth disease (FMD), molybdenum gout, endemic osteoarthritis or Kashin-Beck disease, endemic cardiomyopathy (Keshan's disease), selenosis, boric enteritis, endemic nephropathy etc.;

- of epidemic importance – it can be a transmission factor of pathogens of infection diseases and invasions to people: enteric infections of bacterial (typhoid, paratyphoids А and В, bacillary dysentery, cholera, coli-entheritis), viral (virus A hepatitis, enterovirus infections: poliomyelitis, Coxsackie virus infection, ЕСНО) and protozoa ethiology (amebiasis, lambliosis); zooanthroponosis (types of leptospirosis: infectious jaundice or Vasyl’yev – Vail disease, anicteric leptospirosis, brucellosis, tularemia, anthrax); mycobacteria of tuberculosis; spore-forming clostridia – pathogens of tetanus, gas gangrene, botulism; geohelminthosis – ascaridiasis, trichocephalosis, ankylostomiasis.

All indices are divided into direct (allow to assess the level of soil contamination and level of danger for population health directly from the results of laboratory analysis of taken samples and indirect (allow to draw a conclusion of the existence of soil contamination, its prescription and duration by comparison of the results of soil laboratory analysis with test clean soil of the same type, which was taken as a sample from non-contaminated areas).

Sanitary number of Khlebnikoff – is a ratio of humus nitrogen (pure soil organic substance) to total organic nitrogen (consists of humus nitrogen and nitrogen of strange for soil organic substances that contaminate it). If soil is pure, sanitary number of Khlebnikoff equals to 0.98-1.

Soil coli-titer – is a minimal amount of soil in grammas, in which one bacteria of colibacillus group is found.

Soil anaerobe titer (perfingens-titer) – is a minimal amount of wastes in grammas, in which an anaerobic clostridia is found.

Soil microbial number – is a number of microorganisms in one gram of soil that grew up on 1.5% beef-extract agar at temperature 37⁰С during 24 hours.

Не нашли, что искали? Воспользуйтесь поиском: