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

Figure 4.24. 
Nitrogen 
fixation amounts in 
nature and by human 
activity on a global scale 
Figure 4.25. 
Nitrogen 
compound fallout 
(mg N /m
2
/year) 
with atmospheric 
precipitation – changes 
in the amounts during 
the last centuries and a 
forecast 

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72 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
 4.2.4.  Phosphorus biogeochemical cycle
The environ mental processes and the quality of the environ-
ment depend not only on macro-elements but also on substances 
that occur only in very small amounts in nature. Examples of such 
substances include phosphorus, many metals and their compounds 
and other elements, such as iodine, bromine, arsenic, selenium 
and others. Phosphorus is particularly important for sustaining life 
processes in living organisms, as it is a component in the genetic 
information  carrier  molecules  –  deoxyribonucleic  acid  (DNA)  and 
ribonucleic acid (RNA), in many proteins as well as in the molecules 
responsible  for  cellular  energy  transport  –  adenosine  triphosphate 
(ATP)  and  adenosine  diphosphate  (ADP).  The  phosphorus  cycle 
(Figure 4.26) has a pivotal significance because phosphorus is often 
a limiting factor for the development of living organisms, i.e. the 
amount of phosphorus available for the development of organisms 
determines the intensity of their growth.
Soils
Rivers
Runoff
Agricultural,
industrial,
household utilisation
Terrestrial living
organisms
Vegetation
Production of phosphate
fertilisers and compounds
Sedimentation 
Marine living organisms
Phosphate
sedimentary rocks
The phosphorus cycle differs from the cycles of other elements 
(carbon, nitrogen, sulphur and others) because it does not contain 
substances in gas phase as most phosphate compounds are non-
volatile or solid. The amount of phosphorus compounds in the atmo-
sphere is small, and they are usually extracted from the litho sphere’s 
sedimentary rocks in the form of various apatites (mostly in the 
form of calcium phosphates) that have formed in shallow seas tens 
of millions years ago. When herbivores consume plants, phosphates 
Figure 4.26. 
Phosphorus 
biogeochemical cycle

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4. HUMANS AND THE ENVIRONMENT
 73
enter the bodies of these animals. With their excrements or decay 
after death phosphates are returned to the soil and waters. Part of 
phosphorus compounds are bound as stable chemical compounds 
in the soil and marine sediments, forming phosphate sedimentary 
rocks. The natural cycling of phosphorus com pounds is not in tense; 
there fore, sedimentary rocks that contain phosphorus are con-
centrated in just a few regions of the world, and their weathering 
takes place slowly.
Phosphorus compounds are predominantly (~90%) used as in-
or ganic fertilisers in agriculture. The estimated global utilisation 
of fertilisers is 15 million tons per year. The second major area of 
phos phorus compound utilisation is in detergents. Phosphorus com-
pounds are added to detergents as water-softeners. Just like after the 
de composition of living organic matter, virtually all areas of use of 
phos phorus compounds end up with their runoff into the hydrosphere 
after utilisation, intensifying the processes of eutrophication in 
waterbodies. In any case, human activity has cardinally changed the 
nature of phosphorus flow in its biogeochemical cycle.
References
Begon M., Townsend C., Harper J. L. (2005) Ecology. From Individuals to 
Ecosystems. Boston: Blackwell Pub.
Berner E. K., Berner R. A. (1996) Global Environment. Water, Air and 
Geochemical Cycles. N.Y.: Prentice Hall.
Botkin D., Keller E. (2000) Environmental Science: Earth as a Living Planet. 
N.Y.: Wiley and Sons.
Enger E. D., Smith B. F. (2006) Environmental Science: A Study of 
Interrelationships (10
th
 ed.). Boston: McGraw Hill.
Geochemical Cycles. (1991) Chapter 23 in Inorganic Geochemistry 
(ed. Faure G.). N.Y.: Macmillan Pub.
Lovelock J. (2007) The Revenge of Gaia. London: Penguin Books.
Nebel B. J. (1990) Environmental Science: The Way the World Works. N.Y.: 
Prentice Hall.
Rydén L. (ed.) (2003) Environmental Science. Uppsala: Baltic University 
Press.
Biogeochemical Cycles. Accessible: www.enviroliteracy.org/subcategory.
php/198.html.
Environmental Microbiology. Accessible: www-micro.msb.le.ac.uk/109/
Environmental.html.
Leopold Education Project. Accessible: www.lep.org/.
World Resources Institute. Accessible: http://materials.wri.org/topic_data_
trends.cfm.

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5. GLOBAL ENVIRONMENTAL PROBLEMS