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Soil chemistry

It has now been established that the human body contains about 60 different chemical elements, which is about 0.6% of the total weight. The presence of trace elements, even in small amounts, is constantly associated with their role in the absorption of nitrogen and photosynthesis. Only to maintain the normal composition of human blood, about 25 microelements are needed, and more than 30 are included in breast milk. The degree of provision of microelements with plant and animal organisms is directly dependent on their presence in the earth's crust (soil). It was at this moment that academician V. Vernadsky first pointed out. Based on this A.P. Vinogradov created the doctrine of abnormal biogeochemical provinces (territories), where the absence or excess of one or another element leads to the appearance of endemic diseases (biogeochemical endemic). In 1958, there were 14 natural biogeochemical provinces in the territory of the former USSR, and by 1990 their number doubled due to a deeper study of new territories.

At the same time, as a result of human activities, a huge amount of chemicals directly or indirectly enters the soil, which can significantly change its chemical composition.

All chemicals entering the soil can be divided into 2 groups:

I. Chemicals introduced into the soil systematically, purposefully, in an organized manner:

a) pesticides (up to 90-100 thousand tons per year);

b) mineral fertilizers;

c) soil builders;

d) plant growth stimulants, etc.

Only in the event of excessive application to the soil do they become pollutants.

II. Chemicals that accidentally enter the soil with man-made liquid, solid and gaseous wastes. Geographically, this is associated with specific types of industry, and therefore with a certain type of chemical pollution. These territories, of course, suffer from an excess of certain chemicals. In Russia, there are about 40 territories that are defined as artificial biogeochemical provinces. Areas with an excess of lead, fluorine, cadmium, waist, bromine, mercury compounds and even beryllium have already been taken into account. These substances are included in the biological cycle and, of course, do not pass the person. The danger of compounds of both the first and second groups is determined by their toxicity, blastomogenic, allergenic, mutagenic, embryogenic and other types of exposure.

What is happening now in the process of soil contamination with chemicals, scientists call the "chemical" attack of an uncontrolled process on humans. Calculations based on geneticists' data show that by 2000 over 30% of people born in the last 30 years will have genetic abnormalities. Causing damage to the environment and, above all, soil, a person acts as a suicide.

Chemicals of exogenous origin, when they accumulate in the soil, almost completely suppress the entire biocenosis of the soil and distort self-cleaning processes.

Already, the increased level of the population’s disease, the frequency of deformities, developmental anomalies, physical development disorders and the formation of the psyche are closely linked to chemical pollution in certain areas.

Soil pollution inevitably leads to degradation of the human environment.

Evaluation of epidemiological issues related to soil is related to elucidation of the degree of its contamination with organic substances.

In a clean, unpolluted soil, not many infectious agents live. These are mainly causative agents of wound infections (tetanus, gas gangrene), botulism, anthrax. These are spore microorganisms and their spores remain viable for up to 25 years.

The soil is constantly contaminated with organic substances and always contains pathogens of intestinal infections (dysentery, typhoid fever), the survival periods of which can vary from several months to a year and a half, and poliomyelitis - up to 110 days.

Soil plays a specific role as a helminthiasis transmitter, being an intermediate development environment. Ascaris eggs can remain viable in soil for 7-10 years.

Soil contaminated with organic substances contributes to the development of rodents, which are sources and carriers of pathogens of especially dangerous infections (rabies, plague, tularemia).

Contaminated soil is a favorable site for the development of flies (especially the synanthropic “housefly” flies). The presence of a large number of flies is a clear indicator of health problems, because indicates a violation of the terms for the removal of solid waste from the village. The development period of a fly from a larva to a mature individual is from 4 to 7 days. In addition, flies themselves are very active carriers of pathogens, primarily intestinal infections.

The soil is a natural receiver of all the waste of human life. He wrote about this in the middle of the XIX century. Hygienist Rubner: "The only place that meets the requirements and is intended by nature itself to perceive organic waste is the soil and all conditions are given in the soil so that, thanks to the processes occurring in it, various organic substances turn into the same forms of inorganic compounds in the form of which they are essential nutrients for plants. " These processes, described by Rubner, are self-cleaning processes of the soil that occur under the influence of a number of factors (physical, chemical and biological).

Under the influence of physical factors (sun, drying), a significant part of the pathogenic microflora dies. Under the influence of chemical factors (oxygen of the air and soil), organic substances (fats, carbohydrates) are oxidized to carbon dioxide and water, and nitrogen-containing substances decompose into amino acids and undergo subsequent oxidation, nitrify. An essential role is played by the microorganisms Nitrosomonas and Nitrobacter. As a result, mineral substances are formed that are absorbed by plants.

In the intensity of the soil self-cleaning process, the phenomenon of gummification is very important. As a result of the complex interaction of chemical reactions, the actions of mesophilic and thermophilic microorganisms, a complex organic substance, humus, is formed, which includes humins, carbohydrates, fats, organic acids and a number of carbon compounds. The peculiarity of humus is that it is not able to rot and, therefore, cannot become a breeding ground for microorganisms, especially pathogenic ones. Of particular importance in inhibiting the growth and development of undesirable microflora, in its subsequent death, is the action of bacteriophages and antibiotics. As a result of these complex processes, the soil becomes epidemiologically safe. The composition of soil air becomes stable.

A sanitary assessment of the soil, namely the assessment of the degree of pollution by organic substances, is carried out on a number of indicators.

A decrease in the amount of oxygen, an increase in the percentage of carbon dioxide, the appearance of methane and hydrogen are the result of pollution.

During long-term monitoring of the processes of soil self-cleaning, it was found that after severe pollution with a coli titer of 0.0001 g, only after a year do the indicators reach the norm (coli-titer 1.0).

Clean soil performance:

1. By number: - 0 larvae of flies on an area of ​​0.25 m

2. helminth eggs per 1 kg of soil - coli titer - anaerobic titer - 0, The sanitary number (C) B (humus nitrogen) should be close to 1; C = -

A (total org. Nitrogen)

3. The composition of soil air at a depth of 1 m:

CO2 - 0.38-0.8%,

O2 - 19.75-20%,

CH4 - absent

H2 - absent

Again recalling Rubner’s words that the soil is a natural receptor of all garbage, we must take into account the relativity of this position. The compensatory forces of the soil itself are sufficient only with very little quantitative pollution of the soil. A sharp increase in the load on soil processes leads to the fact that self-cleaning processes are inhibited, soil biocenosis changes. And an increase in garbage leads to the following disadvantages:

1. Change in air. When waste is decomposed into the air, ammonia, hydrogen sulfide, methane, indole, and skatol are released; with strong drying, light objects rise into the air.

2. Dramatically increases the pollution of open water, as well as groundwater and other aquifers.

3. Severe surface pollution in the settlements.

Given all this, cleaning populated areas of solid and liquid waste is a very important sanitary and hygienic task. Cleaning up a settlement should be a unified system of measures covering the entire territory of the settlement. The processes of collection, removal, cleaning of the territory and neutralization of garbage should be mechanized to the maximum extent possible, and the contact of the population and the cleaning personnel with garbage should be excluded or minimized as much as possible.

Waste Classification:

- solid;

- liquid.

Currently, the removal of liquid wastes and their disposal is not an acute problem. Liquid sewage in the presence of sewage enters a closed network, they do not pollute neither the soil, nor air, nor buildings, nor courtyards. And finally, fusion of liquid waste through pipes is economically cheaper than removal.

More difficult is the case with solid waste. Sanitary cleaning of solid household waste is one of the most urgent problems of populated areas: cities, towns, villages. The significance of this problem is determined by the fact that throughout the world there is a process of increasing the amount of household waste per 1 person. The higher the level of improvement, the level of culture of our life, the greater the amount of garbage per person. The level of improvement of our lives is steadily increasing, respectively, and the annual increase in municipal solid waste is a constant figure - 5-8% of the total.

For sanitary workers, the organization of cleaning up populated areas is also of particular importance because the issues of the disposal of accumulated garbage around the world have not yet been adequately resolved. Suffice it to say that in Western Europe, 70% of all municipal solid waste, and in the USA, 85% are disposed of in landfills, which are very often a random collection of garbage. Such an “organization” of treatment will inevitably lead to a huge soil pollution that is growing from year to year, which is certainly dangerous for public health. Only the correct organization of the removal of solid waste from populated areas using existing methods for their disposal can prevent undesirable consequences.

How to organize the cleaning of populated areas from solid household waste?

Sanitary cleaning always has three stages: waste collection, storage, removal to the place of disposal. In our country, all this work is done by a special organization - communal authorities (beautification trust, utilities, etc.). The duties of the sanitary authorities include verifying the correctness of the adopted treatment system and monitoring the places of collection, storage and disposal of waste. When organizing the collection of municipal solid waste, you need to know their qualitative and quantitative composition.

In the qualitative composition of municipal solid waste (garbage), the main components can be distinguished, the amount of which will determine the possibility of recycling garbage by different methods. These are food waste, paper, solid non-recyclable parts (coal, glass, ash). These components will be found in garbage of different origin, but their quantity will depend on the climatic zone, season of the year, level of improvement and historical habits of the population. So, if we take garbage from different cities of the world, then the most food waste (62%) is in France, ash (57%) is in England, paper (65%) is in Finland. The amount of food waste and paper in Russia’s garbage is about the same, but the composition of the garbage is uneven in certain cities: in the garbage in the cities of Donbass, for example, 50% of coal, and in St. Petersburg garbage there are very few food waste, etc.

The main thing you need to know about the quality of garbage is its epidemiological significance.
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