Māris kļaviņŠ, azamat azizov, JĀnis zaļoksnis environment, pollution, development: the case of uzbekistan

136 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
 7.3. 
 Carbon compounds in the atmosphere 
Carbon is the most important element forming the living 
organisms. Carbon in the atmo sphere is in the form of carbon 
mon oxide (CO), carbon dioxide (CO
2
) and methane (CH
4
), and the 
presence of these gases has a significant impact on the atmo spheric 
properties (heat balance) and hence the climate on the Earth. 
Therefore, the growing carbon monoxide emissions may become 
a  factor  that  can  adversely  affect  the  environ mental  processes.  It 
is estimated that over the past 100 years, anthropogenic CO
2
 has 
increased by an average of 2.5% per year. CO
2
 content in the air 
is  also  affected  by  deforestation.  During  the  20
th
 century carbon 
dioxide  emissions  have  significantly  increased,  and  in  the  period 
from 2000 to 2005 they had already reached an average of 26.4 GtC 
CO
2
 per year. It is estimated that, depending on the population 
growth trend, the volume of carbon dioxide emission can reach up to 
35.8 GtC / per year in 2100. 
Carbon dioxide concentration in the atmo sphere has risen from 
280 parts per million in the pre-industrial era to 379 parts per 
million in 2005. Researching the air enclosed in the continental 
glacier ice, it has been proved that the concentration of CO
2
 today 
is  significantly  higher  than  it  was  during  the  last  650  000  years 
(180-300 ppm). Other greenhouse gas concentrations (e.g., methane 
CH
4
, nitrogen (I) oxide N
2
O) have also gon up significantly.
Carbon monoxide CO (charcoal fumes) can be important in the 
context of the human living and working environ ment pollution. 
The total amount of CO in the atmo sphere of the Earth is evaluated 
at 530 million tons, and it remains in the atmo sphere from 36 
to 110 days. The main sources of emission are various natural 
processes: decomposition of living organisms (especially green 
plant chlorophyll decomposition), metabolic processes of plants and 
especially of marine organisms. A serious source of carbon monoxide 
is a variety of photochemical processes (especially methane 
oxidation), in which CO is released as a by-product.
Anthropogenic  carbon  monoxide  emission  sources  account  for 
about 6% of its total quantity. The main sources of anthropogenic 
emissions are the internal combustion engines, their exhaust gas, as 
well as products of fossil fuel incomplete combustion. Particularly 
dangerous in the context of the human living environ ment pollution 
is carbon monoxide. In everyday life the sources of danger can be 
gases resulting from incomplete combustion in furnaces, stoves and 
other heating systems, automobile exhaust fumes, particularly in 
confined spaces.
Carbon monoxide transformation processes are predominantly 
mediated by hydroxyl and hydroperoxide radicals via singlet oxygen 
To denote the air pollu‑
tant concentrations often 
their concentrations are 
expressed in parts of 
volume and number: 
respectively: parts per 
million – ppm; – parts per 
billion; – parts per trillion. 
This designation refers 
to the concentration of 
the substance in the total 
air quantity of 300 ppm 
means that the million 
of gas molecules consti‑
tuting the air contains 
300 molecules of the 
respective greenhouse 
gas, or a million volume 
units of air (such as 
cubic centimetres – cm
3
) 
contains 300 cm
3
 of the 
respective gas.

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7. AIR POLLUTION
 137
or ozone. The prominent role of soil in binding carbon monoxide 
should also be noted. It is determined by the activity of soil 
microorganisms.
Given the high toxicity of carbon monoxide, especially in the 
human living environ ment, it is essential to reduce the emissions 
resulting from various combustion processes. First of all, it can 
be achieved by controlling the internal combustion engine gas 
composition.  CO  content  declines,  when  «leaner»  (poorer  in  fuels) 
air/fuel mixtures are used and the exhaust gas catalytic oxidation is 
carried out.
The  toxic  effect  of  carbon  monoxide  is  based  on  its  ability  to 
replace the oxygen in haemoglobin, forming carboxyhaemoglobin, 
which is unable to transport oxygen. Carboxyhaemoglobin formation 
reaction is reversible, therefore, in case of poisoning by carbon 
monoxide inhalation of air or pure oxygen can restore the ability of 
haemoglobin to carry oxygen.
If carboxyhaemoglobin reaches 10-20% of the total haemoglobin 
in the blood, the poisoning symptoms include mild headache, 
fatigue, discomfort, at 20-30% dizziness can start to appear, loss of 
consciousness can occur, but if 60-70% of haemoglobin are converted 
into carboxyhaemoglobin, the outcome is lethal (Table 7.5).