Hydrosphere is a water medium, which includes surface and groundwater. Surface waters are mainly concentrated in the world's oceans, containing about 91% of all the water on Earth. The surface of the oceans (water area) is 361 million per square km. It is about 2.04 times the area of the land - the territory occupying 149 million square km (Cunningham & Cunningham, 2011). If an even layer of water was spread over the earth, then it would cover it as thick as 3,000 meters. The water in the ocean (94%) and below ground is salty. The amount of fresh water is 6% of the total volume of water in the world, with a very small proportion of 0.36% available in locations easily accessible for production.
Every person on the earth consumes an average of 650 cubic meters of water per year (1,780 liters per day). However, to meet the physiological needs 2.5 liters per day are enough, i.e. about 1 cubic meters per year. Large amount of water is required for agriculture (69%), mainly for irrigation; 23% of water for industry; 6% is spent in the home. Water is not only the condition of life of an individual organism. Without it, it would be possible to exist for the biosphere of life on Earth, because the cycling of matter and energy in the biosphere is only possible with the participation of water. In the course of the water cycle from the ocean surface evaporates annually 453,000 cubic meters of water.
Thus, it is very important to preserve this valuable resource of life on the planet. However, due to actions of people, today there is a huge problem of oceanic water pollution. One of the main sources of pollution is contamination of oil and oil products (Spiro, Purvis-Roberts & Stigliani, 2012). It leads to the appearance of oil spills, which complicates the processes of photosynthesis in the water due to the termination of access to sunlight and causes the death of plants and animals. Each ton of oil creates an oil slick on the water area of 12 sq km. Restoring damaged ecosystems takes 10 - 15 years.
Sewage disposals pollution from industrial production, mineral and organic fertilizers as a result of agricultural production, as well as communal waste water pollution is another important problem. It leads to eutrophication of water – the enrichment with nutrients, resulting in excessive growth of algae and the death of other ecosystem ponds with stagnant water (lakes and ponds), sometimes leading to waterlogging of a land area.
Bacterial and biological contamination happens due to different pathogens, fungi and algae. World economy gets rid of 1500 cubic kilometers of wastewater every year with varying degrees of cleanness, which require 50 - 100 - fold dilution to give them natural properties and further purification in the biosphere. These do not include waste waters of agricultural production. Global river flow (37.5 - 45 of cubic km per year) is insufficient for the necessary dilution of wastewater. Thus, as a result of industrial activities, fresh water has ceased to be a renewable resource.
Pollution with heavy metals violates the livelihoods of aquatic organisms and humans. Pollution with acid rain leads to acidification of water bodies and loss of ecosystems. Radioactive contamination is caused by discharge of radioactive wastes. Mechanical pollution increases the solids content in the water body. Thermal pollution is caused by discharge into water bodies of heated water from thermal and nuclear power plants (Botkin, Keller & Rosenthal, 2012). It leads to the mass development of blue - green algae, the so-called algal blooms, reducing the amount of oxygen and negative impact on the flora and fauna of water bodies.
An important role in the fight against pollution of the seas plays the International Convention for the Prevention of oil pollution at sea. It was adopted in 1958 and amended in 1960 and 1971. In 1958, there was created the Inter-Governmental Maritime Consultative Organization, the main role of which is initially limited to the control of compliance with the provisions of the Convention.
Attaching great importance to the fight for the protection of the marine environment, in London in October 1973 was held the Conference that adopted the International Convention for the Prevention of Pollution from Ships. 1973 Convention applies not only to oil, but also to other harmful substances transported, as well as wastes (sewage, garbage), ship-generated as a result of their use. The Convention contains an article, according to which each vessel is required to have a certificate - that the hull, machinery and other equipment comply with the rules to prevent pollution of the sea. Compliance with this article is checked during special inspections of ships entering the ports. Violators get any tangible sanctions.
The previous agreement guarded the purity of the seas only in a relatively narrow band of the so-called exclusion zones. Now the "exclusion" becomes all the world's oceans. The Appendices to the main document set out international standards of permissible discharges, recommendations for shipborne equipment necessary to preserve the purity of the sea. The Convention establishes particularly strict standards of oil in water discharged by tankers. If the tonnage is more than 70 thousand of gross registered tons, they must have a special capacity for receiving clean ballast (Vörösmarty et al., 2010). They are banned to ship oil. For all special areas (Baltic, Mediterranean, Black Sea, etc.), there is adopted a single regime: a complete ban for discharge of oily water from tankers and dry cargo vessels with a capacity of more than 400 gross register tons. All discharges from them should only be pumped by onshore reception facilities.
References
Botkin, D. B., Keller, E. A., & Rosenthal, D. B. (2012). Environmental science. Wiley.
Cunningham, W. P., & Cunningham, M. A. (2011). Principles of environmental science: inquiry & applications. McGraw-Hill.
Spiro, T. G., Purvis-Roberts, K., & Stigliani, W. M. (2012). Chemistry of the Environment. University Science Books.
Vörösmarty, C. J., McIntyre, P. B., Gessner, M. O., Dudgeon, D., Prusevich, A., Green, P., & Davies, P. M. (2010). Global threats to human water security and river biodiversity. Nature, 467(7315), 555-561.
