WASTES IN THE SEA — WALLEN 387 



actions of absorption and adsorption, flocculation, ion exchange, pre- 

 cipitation, coprecipitation, and mineralization. Working in conjunc- 

 tion with these physical-cliemical forces is gravitation, which acts on 

 the floes and aggregates of particles to settle theni. Attractive forces 

 between the suspended and the dissolved particles are critical factors 

 in sedimentation. Also important are the chemical characteristics 

 of the wastes and the composition of seawater itself. 



FLOCCULATION 



Certain elements have the peculiar property of forming gelatinous 

 precipitates when subjected to an aqueous alkaline medium. Alum- 

 inum and iron are the principal elements of concern in oceanic waste 

 disposal. Aluminum-rich wastes ndded to sea water form a gelatinous 

 precipitate. Release of wastes containing iron also results in rapid 

 precipitation at sea. First a characteristic green color of ferrous 

 hydroxide appears. Then after oxidation has occurred, a flocculent, 

 red precipitate appears vfhich is characteristic of ferric hydroxide. 

 Both of these constituents can scavenge ions having the opposite 

 charge as they aggregate, exchange, and settle to the bottom. 



Rivers often carry a high clay and silica content into the sea. These 

 constituents are chiefly colloidal and negatively charged. They floccu- 

 late when subjected to the cations present in sea water. Such floes 

 can be dispersed and reformed by chemical processes encountered at 

 different depths in the sea. 



ADSORPTION 



Wlien man adds particulate matter by waste disposal, the wastes 

 may be adsorbed to alter the rate of sinking and change their avail- 

 ability to man. The nature of adsorption of solutions is not clear. 

 The physical and chemical characteristics of finely divided particles 

 appear to bind molecules to the surface of solids in suspension on 

 a more or less permanent basis. The degree and permanency of ad- 

 sorption depend on the relationship between charge and size of ionic 

 particles, and upon the charge and topographical character of the 

 adsorbing surface. 



Dissolved radioactive isotopes from fallout or from disposal of 

 liquid wastes may be readily adsorbed by particulate matter in sea 

 water. Sinking particles fall through the water, and eventually come 

 to rest on the bottom. Cerium 144 apparently sinks at a rate of 

 from 50 to 100 meters per month, which indicates its association with 

 organic particles. Promethium 147, which sinks at rates much faster 

 than 100 meters per month, seems to be associated principally with 

 inorganic particles. 



