1. Illustrate the Nitrogen cycle as essential atmospheric cycle, define the five processes in the nitrogen cycle

The Nitrogen Cycle

The nitrogen cycle is the set of biogeochemical processes by which nitrogen undergoes chemical reactions, changes form, and moves through difference reservoirs on earth, including living organisms. Nitrogen is required for all organisms to live and grow because it is the essential component of DNA, RNA, and protein. However, most organisms cannot use atmospheric nitrogen, the largest reservoir. The five processes in the nitrogen cycle -- fixation, uptake, mineralization, nitrification, and denitrification -- are all driven by microorganisms. Humans influence the global nitrogen cycle primarily through the use of nitrogen-based fertilizers. Nitrogen is an incredibly versatile element, existing in both inorganic and organic forms as well as many different oxidation states. The movement of nitrogen between the atmosphere, biosphere, and geosphere in different forms is described by the nitrogen cycle (Figure 1), one of the major biogeochemical cycles. Similar to the carbon cycle, the nitrogen cycle consists of various storage pools of nitrogen and processes by which the pools exchange nitrogen (arrows).

2. Consider the problem of transboundary pollution of the hydrosphere on the concrete example.

Transboundary pollution is the pollution that originates in one country but is able to cause damage in another country’s environment, by crossing borders through pathways like water or air. Pollution can be transported across hundreds and even thousands of kilometers. The incredible distances that pollution can spread means that it is not contained within the boundaries of any single nation. This is why it is called ‘Transboundary Pollution’. One of the problems with transboundary pollution is that can carry pollution away from a heavy emitter and deposit it onto a nation whose emissions are relatively low. Another problem with transboundary pollution relates to the quote above. Due to the fact that ‘All things connect’, the heavy pollution that is evident in the developed world also becomes evident in remote areas. For an example of how transboundary pollution becomes visible in a remote area like the Arctic, see the Arctic Haze fact sheet

3. Describe the mechanism of photochemical smog formation.

Photochemical smog is a unique type of air pollution which is caused by reactions between sunlight and pollutants like hydrocarbons and nitrogen dioxide and sulphur dioxide.

“Wet smog” (London type) - sulfur dioxide and water vapors.

“Dry type” (Los Angeles type )- excess of ozone +dry air, gassy, intense solar radiation.

The photochemical smog is often invisible, it can be extremely harmful, leading to irritations of the respiratory tract and eyes. In regions of the world with high concentrations of photochemical smog, elevated rates of death and respiratory illnesses have been observed.

4. Features of land degradation resulting from human activities.

’Land degradation’ means reduction or loss of the biological or economic productivity and

complexity of rainfed cropland, irrigated cropland, or range, pasture, forest and woodlands

resulting from land uses or from a process or combination of processes, including processes

arising from human activities and habitation patterns, such as:

(i) soil erosion caused by wind and/or water;

(ii) deterioration of the physical, chemical and biological or economic properties of soil;

and

3. long-term loss of natural vegetation.