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

 4.2. 
 Cycling of elements and energy on the earth
The cycling of substances and elements is maintained by the 
flow of energy reaching the Earth from the Sun. The flows of energy 
govern the physical processes (for example, water evaporation and 
condensation and atmo spheric circulation that creates wind) as well 
as chemical reactions occurring in the environ ment. The energy of 
the Sun makes the development of living organisms possible. Both 
chemical elements (for example, nitrogen, magnesium, sulphur) 
and substances (for example, water) are subject to biogeochemical 
cycling. Many elements that participate in the cycling of substances 
constitute the basic building blocks of living organisms. Carbon 
and oxygen make up to 80% of the mass of a human being. Other 
elements are found in trace amounts in the Earth’s crust and in water; 
still, they are indispensable for sustaining life processes (for example, 
phosphorus, boron, copper).
Thus, both biological and geological processes govern the 
cycling of substances and elements, and, essentially, the concept of 
matter cycling discloses the nature of geological changes, physical 
processes and chemical reactions in the environ ment as well as 
The elements, substances 
and energy of the Earth 
are in the process of 
continuous cycling, 
which is described by 
the cycles of substances 
called biogeochemical 
cycles – because they 
encompass a variety of 
chemical conversions 
and geological processes, 
and living organisms take 
an active part in these 
cycles. The source of 
elements (for example, 
oxygen, sulphur, carbon) 
usually is the lithosphere. 
From there substances 
can make their way into 
the atmosphere and 
hydrosphere through 
volcanic eruptions and 
weathering of sedimen‑
tary rocks. Substances 
and elements also 
enter the atmosphere 
from the hydrosphere. 
Moreover, the processes 
related to water cycling 
in nature are crucial. 
Living organisms in the 
biosphere assimilate 
substances from the 
lithosphere, hydrosphere 
and atmosphere, and 
when they die, the 
substances return to the 
environments related 
with the biosphere.

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4. HUMANS AND THE ENVIRONMENT
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transformations of biological systems (living organisms). The 
cycling of substances in the geological environ ment includes the 
processes that began after the Earth was formed. During the Earth’s 
formation process, a solid crust was generated, and it was affected 
by periodic eruptions of the Earth’s liquid inner, reaching the Earth’s 
surface  (Figure 4.14)  and  creating  extrusive  magmatic  rocks.  The 
composition of these rocks changed during the process of their 
erosion (disintegration), making sedimentary rocks. The latter, in 
turn, compacted, creating metamorphic rocks (for example, marble 
originated from the metamorphism of limestone).
Almost  all  the  minerals  on  the  Earth  have  originated  in 
geological processes. The minerals that have formed in the Earth’s 
interior or on its surface can remain almost unchanged for a very 
long time. If the physical and chemical conditions and composition of 
the environ ment undergo significant changes after the minerals have 
formed, their original properties and composition are transformed: 
they start weathering, new minerals and their aggregates are 
formed, and these new formations are more stable in the new 
conditions. These transformations of minerals take place constantly. 
There are minerals that change so slowly that these changes are not 
commensurable with the human lifespan or even with geological 
time. In contrast, there also are minerals that are unstable and can 
rapidly  change  under  the  influence  of  sunlight,  air  or  moisture.