Effect of man on biogeochemical cycles

In the ecosystems, for example, in a forest without any activity of man, an almost closed circulation of biogenic elements exists. In fact, the production of organic matter depends on the quantity of nutrients originally present in water and parent rock (mineral), on moisture and climatic conditions balancing the equilibrium. However, maxi takes wood from forests, and together with it also a number of chemical elements present in it. 

If man s activity is well-considered and based on scientific knowledge of the material balance, the circulation of elements is only slightly disturbed. The missing elements are substituted by erosive destruction of the mineral rock base and growth of roots into deeper layers. Alternatively, the material balance of nutrients is impaired, which is shown by a decrease in production and change in the species composition in favour of less demand- 

Air forms a gaseous envelope around the Earth. Its physical and chemical properties change markedly with the height above the earth s surface pressure and density of the atmosphere exponentially decrease and the atmosphere gradually passes into the sparse interplanetary gases. The temperature does not change evenly the atmosphere layers have different temperatures depending on how they absorb solar radiation. 

Although the atmosphere consists mainly of gaseous components, it also has a solid component (microscopic particles forming an atmospheric aerosol) and a liquid one (rain, fog). The atmosphere as a whole is in a dynamic equilibrium with its surroundings, with the earth s surface, hydrosphere, biosphere and cosmic space. 

Air has some special properties by which it differs from other natural substance. It is omnipresent, its occurrence is not linked to certain places, it is not necessary to transport it and its use is not limited by any state boundaries. Pure air, free from dust or contaminants of gaseous origin, is an unattainable ideal which does not occur in nature. 

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