WASTES IN THE SEA — WALLEN 391 



Lowman's article, "Marine Biological Investigations at the Eniwetok 

 Test Site," published in 19G0. 



Perhaps the most imcertain factor in evaluating the problem of 

 waste disposal into the ocean is lack of adequate knowledge of the 

 diffusion, mixing, and transport processes m the ocean. So-called 

 ocean rivers have been discovered that carry more water than the 

 largest inland rivers at speeds up to at least 5 knots. One of these 

 rivers, the Gulf Stream, meanders toward and away from shore in 

 such a way as to make questionable its use as a mechanism for diffu- 

 sion. Most oceanographers felt that, because of the possible contami- 

 nation of coastal beaches, the area within the Gulf Stream, at least 

 its southerly reaches, should not be used for disposal of wastes. 



Strong equatorial currents and countercurrents also leave open to 

 question any attempts to dispose of substantial quantities of wastes 

 in these areas. Since the source of such currents is unlaiown, the tend- 

 ency is to avoid consideration of the immediately adjacent waters 

 either north or south of the equator as possible disposal sites. 



In the upper layers of the ocean, even in the absence of strong undi- 

 rectional flow, the transport of radioactive nuclides occurs at a sig- 

 nificant rate. According to Allyn II. Seymour, one year after the 

 1954 test series in the Marshall Islands, some activity from close-in 

 fallout from those tests was found in the North Equatorial Current, 

 with the highest activity in an area about 3,500 miles west of the 

 Bikini-Eniwetok area. The activity in this area was about one-fourth 

 of the naturally occurring radioactivity in sea water. However, it 

 was measurable. 



Low-level wastes introduced into the upper, well-mixed laj'^er of the 

 ocean or into coastal waters will quickly be transported and diffused 

 away from the source. This diffusion process is best understood in 

 tidal and mistratified waters, where three mechanisms may be noted : 

 initial diffusion brought about by the method of introduction, i.e., by 

 jet stream, by release into the wake of a ship, etc. ; primary dispersion 

 due to adjustments in relative density, temperature, etc., in the first 

 hour or two after release; and secondary dispersion due to currents 

 and tidal flow. 



In relatively isolated waters, the mixing of wastes with sea water 

 continues principally by molecular and turbulent diffusion processes. 

 Although for practical purposes molecular diffusion is relatively un- 

 important as compared with turbulent diffusion, molecular processes 

 establish an end point of mixing, and contribute most to the later 

 mixing stages. 



Turbulence adds about one millionfold to the rate of molecular 

 diffusion. Vertical diffusion in surface waters occurs at a rate about 

 one thousand times greater than molecular diffusion. The dispersion 

 rate depends on tidal and other currents, the surface wind speed. 



