(>e 



Atomic Radiation and Oceanography and Fisheries 



elements in the sediments are proportional to 

 the iron or manganese content. In addition, fil- 

 ter feeders show concentrations indicating up- 

 take of undifferentiated particulates. 



Several experiments have been reported in 

 which the reactions between fission product ac- 

 tivities (mixed and individual isotopes) and 

 suspended solids have been studied. In the fol- 

 lowing examples both marine and fresh water 

 experiments are noted. 



Gloyna in Goodgal, Gloyna, and Carritt 

 (1954) noted that 58 per cent of mixed fission 

 product activity (initially less than 1000 cpm) 

 could be removed from solution during cen- 

 trifugation of untreated Clinch River water, 70 

 ppra solids, pH 8.4 and alkalinity 92 ppm (Ca- 

 CO3). No attempt was made to determine 

 which elements were removed. 



Carritt and Goodgal (1954) studied the up- 

 take of phosphate, iodide, iron III, strontium 

 sulphate and copper II on samples of Chesa- 

 peake Bay sediments. Measurements were made 

 under controlled but varied pH, temperature, 

 salinity, concentration of solids, and specific ac- 

 tivities. Of the elements studied strontium, io- 

 dide and sulphate are of interest here — sul- 

 phate because of the similar chemical behavior 

 of tellurium. Iodide showed no uptake at con- 

 centrations applicable to the present discussion. 



Under conditions where strontium carbonate 

 did not precipitate, strontium was absorbed ac- 

 cording to the following isotherm: 



x/m= 0.0032 C"-** 



x/m=jug atoms Sr per milligram of solids 

 C= equilibrium concentration of strontium 

 in jLtg atoms Sr per liter. 



This isotherm was valid over the range 52 to 

 5200 ^g atoms Sr per liter. 



The uptake of sulphate showed strong pH 

 dependence. At pH above 4.5 very little uptake 

 was noted. With decreasing pH, uptake in- 

 creased, suggesting that the bisulphate is more 

 active than sulphate. 



At pH 3.3 (an unlikely marine condition) 

 the uptake followed the isotherm: 

 x/m = 0.0013 C0-S2 



over an initial sulphate concentration range of 

 10». 



Several proposals on ocean waste disposal 

 would allow introduction of packaged waste 

 into the bottom by sea burial. Dispersion of ac- 



tivity would be a slow diffusion process as from 

 concreted wastes or would be delayed until rup- 

 ture of an impermeable container. In either 

 case, the activity released would go into the 

 highly absorptive environment of the sediments. 



One form of packaging for the disposal of 

 active waste has been proposed by Hatch 

 (1954). He has described the problems en- 

 countered with the absorption of fission prod- 

 ucts onto montmoriilonite clays, followed by fir- 

 ing to 800° C, to produce a high density, high 

 specific activity, insoluble waste. When given 

 appropriate pretreatment, it was estimated that 

 fission products could be removed from reactor 

 wastes to yield clays with an activity of about 

 10 curies per gram. The practicability of utili2- 

 ing solids of this kind apparently depends upon 

 the demonstration of long term stability under 

 deep ocean conditions and upon the economics 

 of production and transportation. It should be 

 noted that short term stability tests suggest that 

 the fired montmoriilonite clays would be ex- 

 tremely stable. 



Deep ocean deposits have appreciable base 

 exchange capacities. Revelle measured this to 

 be in the range 30-60 millequivalents per 100 

 gram of solids. Soluble waste components can 

 be expected to react with solids on the bottom 

 surface and to be removed from solution by 

 base exchange reactions, and isotopic exchanges. 

 No estimate seems possible of the depth into the 

 sediments that this kind of reaction would take 

 place. Certainly the surface layer of sediments 

 would become saturated and reaction with deep 

 sediments would be controlled by diffusion into 

 the sediments. 



Further data required 



A survey of available literature reveals many 

 gaps in our knowledge in this field. Basic data 

 on the settling processes of natural sedimenta- 

 tion are few, and the carrying processes by 

 which tracer concentrations of isotopes would 

 be removed from the oceans have been almost 

 entirely neglected. From a practical point of 

 view, the data most needed are measures of the 

 gross sedimentation rate of radioactivity. This 

 would be an integral of the effects of many 

 processes — empirical information that would 

 permit a statement concerning the sedimentation 

 rate of activity without reference to the many 

 mechanisms involved. 



