In addition to the generally known groups of large-scale toxicants 

 (petroleum and its products, heavy metals, chlorinated organic 

 compounds), we should mention two more types of substances, the 

 liberation of which into the environment is quite extensive. We are 

 speaking of volatile organic liquids and gases (dichloroethane, freons, 

 solvents) and carcinogenic substnces, which have blastomogenic 

 properties (polycyclic aromatic hydrocarbons such as benzpyrene). 

 information on the content of such substances in the sea and its 

 orgnisms is as yet sparse; however, the scale of their production and 

 entry into the environment is quite large: the annual rate of 

 liberation of dichloroethane and freons into the atmosphere is at least 

 1 million tons, of volatile organic solvents up to 2 million tons 

 (Marine Environmental Quality, 1971). The total quantity of persistent 

 anthropogenic hydrocarbons (in addition to methane) entering the 

 atmosphere is about 50 million tons per year (Duce et al . , 1974). To 

 this figure we must add the pollution of neritic marine waters and of 

 the open ocean by solid wastes, consisting of various insoluble plastics 

 and organic films, the world production of which is over 20 million tons 

 per year (Marine Environmental Quality, 1971). A significant fraction 

 of these products finally reaches the ocean. For example, the mean 

 content of plastic particles in the Sargasso Sea is 290 g/km 

 (Carpenter, Smith, 1972). 



We also must not forget the processes of eutrophication resulting 

 from the liberation of organic substances, fertilizers, detergents and 

 other compounds of phosphorus and nitrogen, leading to the intensive 

 development of phytoplankton and certain species of benthic algae and, 

 thus, to secondary pollution of the sea with the products of their 

 metabolism and decay. However, these processes, like the processes of 

 thermal pollution (see Chapter II, 3.), are generally localized in the 

 neritic waters or internal bodies of water, and should not be considered 

 to be a global situation. 



Let us attempt briefly to describe the basic structural and dynamic 

 peculiarities of the field of large-scale pollution of the ocean. 



Increased pollution of the euphotic layer . --This distribution 

 feature is rather obvious, since it is the surface waters which are the 

 primary collectors of atmospheric pollution, littoral runoff, sewage and 

 wastes of the most varied composition and origin. Depending on the rate 

 of exchange and renewal of surface waters and, at times, on the rate of 

 biosedimentation processes (Patin, 1970), a certain gradient of vertical 

 distribution of pollution is created in the water; however, the levels 

 of content of toxicants of all kinds generally reach their maximum in 

 the surface layer. 



Increased pollution of the neritic zone . --The available data on 

 pollution of the seas and oceans indicate that there is a gradient of 

 decreasing concentration upon transition from the neritic zone to the 

 open ocean, resulting from the delivery of polluting substances into the 

 sea from the land and their gradual dilution with increasing distance 

 from the source, the localization of many types of human activity 

 causing pollution (navigation, drilling for petroleum) in the shallower 



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