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CHAPTER 6 PRECIPITATION OF FISSION PRODUCT ELEMENTS ON THE OCEAN BOTTOM BY PHYSICAL, CHEMICAL, AND BIOLOGICAL PROCESSES DAYTON E. CARRITT, The Johns Hopkins University and JOHN H. HARLEY, Health and Safety Laboratory, U. S. Atomic Energy Commission Introduction IT HAS been suggested that naturally occurring processes will remove radioactive waste mate- rials from solution or suspension in the oceans, carrying them to the ocean floor where they will be kept out of the human environment until natural radioactive decay destroys them. In this section we will attempt to define the processes by which materials may be carried to the bottom, to note the conditions under which these several processes can be expected to op- erate, and to assess the extent to which these processes have been responsible for the removal of activity to the bottom in cases where bottom accumulation has been measured. It should be noted that the deposition of fis- sion products on the bottom has not been stud- ied in such a way as to permit an evaluation of the mechanisms responsible for the deposition and retention of the activities. Measurements of bottom-held activities have been made pri- marily to estimate the total activity. We will discuss later the kind of information that might be obtained in connection with weapons tests and large-scale tracer experiments, and which is needed for a better evaluation of the extent to which deposition processes remove fission product elements from the ocean. Sources of Fission Products The oceans may receive fission products from two sources, materials from each of which have unique properties important to deposition. The two sources are: (1) Radioactivities resulting from bomb bursts, either in weapons testing or military use of bombs in war time. Partial controls can be put on the location and time of weapons tests to take advantage of desirable dispersal or con- centrating properties of the oceans. (2) Radioactivity obtained from nuclear power production plants and released to the oceans for containment or dispersal. The time and location of introduction of wastes of this type can be controlled to obtain optimum oceanic charac- teristics, and the character of the wastes might be altered by the removal of one or more un- desirable active or inactive constituents. In both cases it can be expected that the fission products will partition into a soluble and an insouble fraction. An estimate of the ele- ments that will appear in each fraction is given in another part of this report. This division into soluble and insoluble frac- tions presents essentially two different systems so far as deposition or dispersal processes are concerned. Deposition and Retention Processes Deposition and retention of fission product waste on the ocean floor will occur when the waste is sufficiently denser than sea water to permit it to settle to the bottom, and when the stability of a waste-bottom component complex is sufficiently greater than the stability of soluble complexes that might form to prevent its re- dissolving. Solid formation The "denser-than-sea-water" requirement can be met when one of two processes occur: (1) the formation of insoluble substances by inter- action of the radioactive components of the wastes with a sea water component, and (2) sorption of the radioactive components of the 60

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Chapter 6 61 Precipitation on the Ocean Bottom wastes by solids naturally occurring in sea water or by solids formed by interaction of non-radio- active components of the wastes with sea water constituents. Certain generalizations can be made with re- gard to the formation of a solid phase — a precipitate, by the interaction of radioactive constituents with sea water components. Pre- cipitation may occur when the solubility product of a substance has been exceeded. Funda- mentally, in order to be able to predict when this condition has been met, knowledge of the ionic activities of the species involved must be known. Ionic activity is used here in the thermo- dynamic sense, and is not related to activity in the radioactive sense. Unfortunately practically nothing is known about ionic activities of fission product elements in sea water. The theoretical approach through this route appears, therefore, to be impractical. The mass of radioactive elements that might be introduced into the ocean from any expected level of power production or foreseeable use of bombs, will be small when compared to the quantities of similar elements already in the ocean. Thus, it is to be expected that chemical precipitation of radioisotopes will occur only in ocean regions where precipitation occurs nor- mally. This process includes precipitation in the usual sense and co-precipitation — the proc- ess in which similar elements are simultaneously removed from solution. For example, during the precipitation of calcium carbonate, stron- tium, a minor element, usually is co-precipitated and carried along with the calcium carbonate. Sorption processes involving inactive solids provide another set of mechanisms that may pro- duce radioactive solids. The solids that are present in sea water or might be produced from inactive waste components are generally finely divided, have large area to volume ratio, and are charged. The sorption of radioactive and in- active dissolved constituents onto the solids, in the ratio of their relative concentration, is fa- vored by these characteristics. Thus, in cases where an element normally present in sea water is known to be taken up by suspended solids it can be expected that radioisotopes of the same or chemically similar elements will also be taken up. The oceans contain inorganic and organic, living and dead suspended solids — all have sorption properties and may remove active and/ or inactive constituents from solution. Settling characteristics The sinking of particles in the sea is usually described in terms of Stokes' Law which as- sumes, in its simplest form, smooth, rigid, spherical particles of a stated diameter and den- sity, sufficiently widely spaced so as not to im- pede one another. It provided an adequate de- scription of the behavior of these solids with a restricted particle size range. For particles larger than about 100 microns (0.1 mm) the law must be modified to take into account turbulence around the particle that has a net effect of re- ducing the settling rate. Also, particles of col- loidal and near-colloidal dimensions, less than TABLE 1 SETTLING VELOCITY OF Qt (IN DISTILLED WATER) IARTZ SPHERES Settling Diameter velocity 1 Time to settle 1000m 0.07 days 1.25 " 125 34 years 39 137 685 2.740 (mm) 1.0 (microns) . . . 1000 (m/day) 14,000 800 8 0.08 0.07 0.02 0.004 0.001 0.1 . . . 100 0.01 10 0.001 . . . 1 1/1024 0 98 1/2048 . . 0 49 1/4096 . . 0.25 1/8192 . 0.12 about a half micron, settle at a rate less than predicted by Stokes' Law, presumably because of charge interaction between particles and dis- solved components. Table 1 gives the settling velocities for par- ticles of a stated size in distilled water, has been calculated from Stokes' Law and is subject to the criticisms noted above. This table is a highly simplified and idealized picture of the actual settling properties of solids that normally occur in the oceans, and especially of particles in the small size range. Particles in this range probably will be the main concern when considering the deposition of fission prod- ucts. They are also in the size range that will permit ocean circulation to alter markedly any predicted location of deposition or of time to reach the bottom. The density and shape factors that effect settling characteristics are important when con- sidering organic solids or living organisms. The density approaches that of sea water which

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62 Atomic Radiation and Oceanography and Fisheries reduces the settling rate, and the shape may vary considerably from the smooth sphere as- sumed for Stokes' Law. The particle-size distribution of solids sus- pended in the ocean as shown by sediments is broad, varying from over a millimeter in di- ameter for sands found near shore, to 0.1 micron or less for sediments taken from the open ocean. The median diameter of open-ocean particles is in the range 1 to 8 microns. The accumulation of solids on the ocean floor is a relatively slow process. Table 2 (Holland and Kulp, 1952) indicates the rate of sedimen- tation on the several parts of the ocean floor. TABLE 2 SEDIMENTATION RATES Fraction of sea Sedimentation Type of sediment water rate x 10-* gm/cm* per year Shelf 0.08 40 Hemipelagic 0.18 1.3 Pelagic 0.74 globigerinaj pteropod J red clay 0.28 0.2 radiohrian} 0.10 0.15 A weighted average gives approximately 0.75 mg/cm2 per year for the oceans. If the area of the ocean floor is 3.6 x 1015 cm2, the total depo- sition will be 2.7 x 10™ grams or 2.7 x 109 tons per year. Retention Prior to actual deposition on the bottom, radioactive solids that have been formed above the bottom may encounter changes in environ- ment that will tend to return them to solution and prevent or hinder deposition. For example, resolution of precipitates with increasing pres- sure (calcium carbonate), releases of radioac- tivity from solids as they fall through uncon- taminated water, vertical migration of organ- isms, and vertical components of circulation are all possible mechanisms that will tend to pre- vent the deposition of radioactive material on the bottom and, when coupled with horizontal circulation features, will tend to disperse the radioactivity over large areas. The retention of radioactive material on the ocean floor once it has been deposited there will depend upon the stability of the floor relative to erosion, to further deposition, and to tur- bidity currents, and upon the chemical features of the bottom relative to those through which the solids have settled. The deep ocean basins are the regions of greatest stability in all respects. Regions near shores and shelves are subject to the greatest variations in deposition and erosion; in regions where rivers enter the seas, relatively wide changes in chemical properties take place. Discussion of existing data Three sources of information give some insight into the probable behavior of fission product elements in sea water. They are: (1) existing information concerning the solution chemistry of the elements in question, (2) the behavior of radioactive debris observed in con- nection with bomb tests in the Pacific, and (3) information concerning the geochemistry of the elements in question. In utilizing information from these sources to assess the probable fate of fission product ele- ments in the oceans the chemical properties of the oceans are of major importance. Table 3 lists the elementary composition of sea water together with an estimate of the amounts of natural activities present. In Table 4 are listed fission product elements, together with their half lives and the equilib- rium quantities that would be in existence after 100 days cooling when formed in connection with 1011 megawatt hours per year of nuclear power production. Also listed are the specific activities that would result were these activities to be mixed throughout the oceans. It will be obvious from a consideration of oceanic prop- erties, presented in other sections of this re- port, that under any practical method of intro- duction of wastes, attainment of uniform specific activity of any given element throughout the oceans will not occur. There will be gradients of radioactivity, decreasing from the region of introduction. The figures for specific activities are, therefore, unrealistic and are included only as a basis for making a better estimate when the effects of circulation and fractionation can be provided. In a few cases, knowledge of the fraction of an element, that would be normally removed by geochemical processes will permit an estimate to be made of the fraction of a radioisotope that will be removed for a given loading. Con-

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Chapter 6 Precipitation on the Ocean Bottom 63 TABLE 3 ELEMENTS IN SOLUTION IN SEA WATER (EXCEPT DISSOLVED GASES)l> mg/kg Element Cl= 19.00% Chlorine 18,980 Sodium 10,561 Magnesium 1,272 Sulfur 884 Calcium 400 Potassium 380 Bromine 65 Carbon 28 Strontium 13 Boron 4.6 Silicon 0.02 -4.0 Fluorine 1.4 Nitrogen (comp) . 0.01 -0.7 Aluminum 0.5 Rubidium 0.2 Lithium 0.1 Phosphorus 0.001-0.1 Barium 0.05 Iodine 0.05 Arsenic 0.01 -0.02 Iron 0.002-0.02 Manganese 0.001-0.01 Copper 0.001-0.01 Zinc 0.005 Lead 0.004 Selenium 0.004 Cesium 0.002 Uranium 0.0015 Molybdenum 0.0005 Thorium < 0.0005 Cerium 0.0004 Silver 0.0003 Vanadium 0.0003 Lanthanum 0.0003 Yttrium 0.0003 Nickel 0.0001 Scandium 0.00004 Mercury 0.00003 Gold 0.000006 Radium 0.2-3 X Natural activities Total in oceans (tons) 2.66 X 10M 1.48 X 10™ 1.78 X 10M 1.23 X 10™ 5.6 X 10" 5.3 X10" 9.1 X10U 3.9 X10™ 1.8 X 10U 6.4 X10U 0.028-5.6 X10U 2 X 10U 0.14 -9.8 X 10U 7 X 10" 2.8 X 10U 1.4 X 10" 0.014-1.4 X 10U 7 X 1010 7 X 1010 1.4 -2.8 X 10M 0.28 -2.8 X 1010 0.14 -1.4 X 1010 0.14 -1.4 X 101 0 7 X10* 5.6 X 10* 5.6 X10* 2.8 X 10* 2.1 X 10* 7 X10* <7 X10t 5.6 X10* 4.2 X 10* 4.2 X 10* 4.2 X10* 4.2 X10* 1.4 X10T 5.6 X10T 4.2 X10T 8.4 X 109 28 -420 Nuclide K" C" Total (tons) 6.3 X1010 56 Rbs7 1.18 X 10U U288 2.8 X10* 2.1 X10T 1.4 X 10* Ra2" 4.2 X101 iSverdrup, H. U., M. W. Johnson, and R. H. Fleming, OCEANS (1942). 2Revelle, R., T. R. Folsom, E. D. Goldberg, and J. D. Isaacs (1955). Curies 4.6 X 10" 2.7 X 10* 8.4 X 10* 3.8 X 10* 1.1 X 10* 8 X 10* 1.1 X 10* versely, observations of the behavior of radio- active isotopes would lead to a better under- standing of the geochemistry of a given element. Operational data Of the fission products listed several are either rare earths or rare-earth-like — such prod- ucts all have very similar chemical properties. All form relatively insoluble hydroxides of the type R(OH)2. The solubility products of the rare earth elements listed by Latimer (1952) all fall in the range 10'20 to 1(T20. Although a quantitative comparison of the conditions that actually exist in the sea cannot be made with these constants, it would appear from the scant information available concerning the quantities of rare earth elements in the sea that marine waters are saturated with respect to these ele- ments and that a major portion of the rare earth elements are dispersed in the sea as solids. This is generally confirmed by American and Japa- nese observations of the distribution of fission product activities in the Pacific following bomb tests. In most cases, however, it is difficult to differentiate between "solid fractions" that have been precipitated as solids by chemical processes, and radioactive solids that have been accumu-

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64 Atomic Radiation and Oceanography and Fisheries lated by microscopic plankton organisms. Both will be collected by filtration or centrifugation. Goldberg (1956), however, noted that informa- tion obtained during Operation WIGWAM suggests a fractionation of a portion of the fission product activities into solids that are col- lected and concentrated by filter feeding or- ganisms. The activity within the filter feeding TABLE 4 FISSION PRODUCT ACTIVITY AFTER 100 DAYS COOLING FROM 10U MEGAWATT HOURS OF NUCLEAR POWER PRODUCTION 1 Specific activity Half- Tons Curies at curies per life (metric) 100 days ton2 94 y 7.3 3.3 X 10* — Sr* 55 d 86 2.3 X 10" 0.128 Sr*0 25 y 463 7.5 X 10" 0.0042 Y*° 62 h — 7.48 X 10" 178 Y" 57 d 111 2.8 X 10" 6,660 Zr* 65 d 152 3.2 X 10" — Mb" .... 35 d 161 6.3 X10" — Rulot ... 45 d 46 1.3 X 10" — Rh"* ... 57m — 1.3 X 10" — Ru™ ... 290 d 35 1.5 X 10U — 30 sec. — 5.15 X 1010 — 8.0 d — 5.2 X 10* 0.0743 33 y 705 5.63 X10M 20.1 2.6 m — 5.1 X 1010 Isotope Kr" .. , Rh1" P" . Csm Bam Ba"° ... 12.5 d 2 La"* ... 1.7 d — Ce"1 ... 28d 45 Pr1* ... 13.8 d 2 Ce1" ... 275 d 490 Pr"1 ... 17m — Pm1" ... 94 y 7.3 Sm"* ... 73y 0.7 0.728 1.5 X 10U 2.14 2.5 X 10U 595 1.5 X 10" 268 1.4 X10U — 1.6 X 10" 386 2.4 X10" — 3.3 X 10' — 2.0 X 10T — 1 Adapted from data of Culler (1954b) and Revelle, et al. (1955). 2 Based on tonnage shown in Table 3. organisms — ones adapted to the removal of particulate material from suspension — showed a high percentage of rare earth elements that previously were noted as probably being pre- dominantly dispersed as solids in the oceans. These organisms were collected in the mixed layer of the sea. About a year after the 1954 nuclear tests were completed. Operation TROLL undertook a survey of the region west from the test site, including the region just off the Phillipines and northward off the coast of Japan (U. S. Atomic Energy Commission, 1956). Seventy water and plankton samples taken during this cruise were analyzed radiochemically. When compared on an equal weight basis (1000 gms wet plankton vs. 1 liter of water) the plankton contained on the average 470 times the activity of the water. Significantly, 80 to 90 per cent of the activity of the plankton was due to Ce144 (and its Pr144 daughter). Cerium is a rare earth. No informa- tion is yet available concerning the species and the relative quantities of organisms responsible for the concentration of activity. A comparison of the total activity per unit weight of macro- and micro-plankton indicated approximately a one and one half times greater concentration by the micro-plankton. It is noteworthy that the observations made on Operations TROLL and WIGWAM revealed a system in which the properties, with the ex- ception of radioactive element content, were es- sentially those of normal sea water. The sys- tem can be imagined as being essentially sea water to which had been added the radioactive material — a procedure which because of the extreme dilution of the contaminant, in a chemical sense, would not affect the sea water properties. Furthermore, these observations were made on samples taken in the mixed layer (the upper 100 to 300 m). These results, though largely qualitative in na- ture, suggest the following conclusions regard- ing the behavior of fission product elements in the mixed layer of the open oceans: 1. Radioactive material will be retained in the mixed layer for periods of at least a year during which time horizontal motion may carry them a few thousand miles. (Operation TROLL and SHUNKOTSU-MARU data.) 2. Rare earth elements appear to be dispersed primarily as solids and accumulated by the plankton. (Operations TROLL and WIG- WAM.) 3. The initial accumulation of rare earth ac- tivities is predominantly by filter feeding or- ganisms, presumably by retention of finely di- vided solids in their feeding apparatus. 4. The cycle of rare earth activities through the biota is unknown. Nevertheless, biological agencies undoubtedly have an important influ- ence in the deposition mechanisms. The physical state of fission product elements in sea water is important in all of the processes that have been previously mentioned. Table 5 sets forth several fission product elements, the percent of total activity present one year after removal from a reactor and an estimate of the

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Chapter 6 Precipitation on the Ocean Bottom physical state of each if dispersed in sea water. The estimates of physical states have been ob- tained from oceanographic studies following bomb tests and from considerations of the "solution chemistry" of the elements. It should be emphasized that the terms "solid" and "solu- tion" are relative terms. Measurements made during oceanographic studies invariably base the division upon filterability. Such a division TABLE 5 AN ESTIMATE OF SOLID AND SOLUBLE FRACTIONS FOR FISSION PRODUCTS IN SEA WATER TABLE 6 GEOCHEMICAL BALANCE OF SOME ELEMENTS IN SEA WATER (FROM GOLD- SCHMIDT, QUOTED IN RANKAMA AND SAHAMA, 1950, TABLE 16.19) Per cent of total activity at end of Physical state in Element one year sea water Sr» 3.8 Solution Sr^+Y" 1.7+ 1.7 Solution + solid Zr* 7.2 Solid Nb" 15 Solid Ru1M 2.5 + 2.5 Mostly in solution Cs1" + Ba1" 1.5+ 1.5 Solution Ce1" + Pr"4 26 +26 Solid Pmm 5.6 Solid obviously will place soluble elements that are utlized by organisms in the solid or solution+ solid category. The settling characteristics of elements so combined will depend upon prop- erties of the organisms. To what extent anoma- lies of this kind are in the estimate above can- not be stated. However, the estimates agree qualitatively with those made from knowledge of the behavior of elements in systems where biological activity is not a major variable. Culler (1954a), has noted that low level ac- tivities discharged to White Oak Creek end up primarily with the clay in a retention basin. The character of the waste was not noted. Krumholz (1954), however, found considera- ble uptake of radioactivity in the biota with subsequent relocation and dispersion in the same region. Geochemical data An estimate of the behavior of several sea water constituents can be obtained from the re- sults of geochemical studies. These studies per- mit an evaluation of the fraction of an element supplied to the oceans that is removed from so- lution. The removal processes may include one or more of those previously mentioned. The results permit no choice of mechanisms. Table 6 lists several elements found in sea water, the Amount present in ocean (ppm) 10 560 Element Na ... Total supplied Transfer percentage 62 16980 K 15 540 380 24 Rb 186 0 2 0 1 Ca . . 21,780 400 1 8 Sr 180 13 7.2 Ba 150 0 05 003 Fe . . 30,000 0.02 0 00007 Y 16.9 00003 0.002 La 11 0.0003 0 003 Ce 27.7 0.0004 0.001 quantities supplied to and present in the oceans and a quantity, the transfer percentage, which is the percentage of "present" to "supplied." Large values of transfer percentage indicate that relatively large fractions of the elements supplied to the oceans stay in solution — small values of transfer percentage that relatively much is removed. Using the transfer percentages listed for cesium, strontium, and cerium, and estimates of the specific activities that would occur in the oceans as a result of 1011 megawatt hours nu- clear power production, the reduction through geochemical processes has been calculated. The figures are given in Table 7. TABLE 7 ACTIVITY REDUCTION BY GEOCHEMICAL PROCESSES Specific activity (c/gm) Element (no removal) Cesium ...... 8.6 X Iff* Strontium ..... 6.8 X 10"* Cerium ...... 1.8 X 10-" Laboratory data Floccing, possible in the disposal of wastes rich in iron or aluminum, may assist in removal of fission products. Unless settling times of nat- ural or artificial floes are short, resolution and biological uptake may reduce the settling factor markedly. Goldberg (1954) has described the copre- cipitation processes with iron and manganese. While none of the fission product elements are treated, analyses show that the amounts of trace Specific Transfer activity percent- after age removal (c/gm) 0.005 4.3 x 10-* 7.2 4.9 X 10-" 0.001 1.8 X 10-"

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66 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 ppm solids, pH 8.4 and alkalinity 92 ppm (Ca- COS). 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 O>-" x/m=/ig atoms Sr per milligram of solids C= equilibrium concentration of strontium in fig atoms Sr per liter. This isotherm was valid over the range 52 to 5200 jig 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 C°-92 over an initial sulphate concentration range of 109. 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 montmorillonite 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 utiliz- 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 montmorillonite 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.

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Chapter 6 67 Precipitation on the Ocean Bottom Nevertheless, for an understanding of the overall process — so that predictions for condi- tions other than those existing at the time of observations can be made, and to provide infor- mation useful to other studies, many individual processes should be studied. The following studies, grouped according to the primary source of information, and thought to be pertinent to the sedimentation and retention problem, would provide some insight into these processes. Ob- viously, information obtained from one group of studies may be of value in the solution of problems in others. Data from weapons tests 1. Measurement of the immediate partition of ,weapons test debris among large-sized immedi- ate fallout, water-borne activity and the air- borne material which may be quite uniformly distributed over the world. 2. Measurement of partition of individual iso- topes in sea water between particulate material and solution. (Dynamic and equilibrium con- ditions) . 3. Mechanism of sorption of radioisotopes on natural suspended solids under the conditions existing in ocean water. 4. Measurement of settling rates of natural in- organic particulates, probably by tracer tech- niques. 5. Measurement of detrital settling rates, in- cluding plankton average life. 6. Measurement of uptake and element differ- entiation in organisms which may become de- trital material. Data from waste disposal experiments Certain studies here can be combined with tracer studies, designed primarily to give infor- mation on basic oceanographic problems: 1. Life expectancy of burial containers. 2. Diffusion rate from concreted or sintered blocks as a function of size, and the concentra- tion and istopic composition of wastes. 3. Regardless of what disposal system is adopted, there will be liquid wastes produced, and studies must be made of liquid waste dis- persal. The pertinent effects will be more re- lated to the weapons test data requirements since this is a surface to bottom transfer. Tracer experiment data 1. Coprecipitation of individual fission products with their stable isotopes normally occurring in sea water, and the particle size distribution of the solids formed, and their sedimentation rate. 2. Similar data on coprecipitation by isomor- phous replacement, for example the carrying of radiostrontium with inactive calcium. 3. Rate of entry of diffused material into the basic biological systems. This includes the bot- tom to surface movement as modified by sedi- mentation. 4. Exchange capacities of sediments for the ra- dioisotope ions in sea water medium, and rate of diffusion of these isotopes into the undis- turbed bottoms. In all studies in which dispersion, partition, concentration and localization occur, measure- ments that would permit a balance sheet to be made (all the activity should be accountable) seem desirable and necessary. SUMMARY The only semi-quantitative data relevant to the problem of activity removal from the ocean surface are the geochemical data. These indicate a reduction factor of 14 for strontium, 2,000 for cesium, and 100,000 for cerium (and proba- bly all rare-earth-type elements). No informa- tion is available on such elements as ruthenium, rubidium, and iodine. Other mechanisms de- scribed may contribute to activity removal, but their effects cannot be evaluated with present knowledge. The reduction factors are for equilibrium con- ditions, and the high sea water activity found a year after the Castle tests (Operation TROLL) indicate that equilibrium is reached slowly. Activity introduced on the bottom through sea burial will be subject to entirely different removal processes. No estimate can be made of their effectiveness. CARRITT, D. E., and S. GOODGAL. 1954. Sorp- tion reactions and some ecological impli- cations. Deep-Sea Research 1:224-243. CULLER, F. L. 1954a. Unpublished results. CULLER, F. L. 1954b. Notes on Fission Prod- uct Wastes from Proposed Power Reac- tions. ORNL Central File No. 55-4-25.

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68 Atomic Radiation and Oceanography and Fisheries GOLDBERG, E. D. 1954. Marine Geochemis- try 1. Chemical Scavengers of the Sea. /. Geol. 62:249. GOLDBERG, E. D. 1956. Unpublished results. Presented at Princeton, N. }., March 3, 4, 5, 1956 meeting of NAS Study Group on Oceanography and Fisheries. GOODGAL, S., E. GLOYNA, and D. E. CARRITT. 1954. Reduction of radioactivity in water. Jour. Amer. Water Works Assoc. 46, No. 1:66-78. HATCH, L. P. 1954. Clay adsorption of high level wastes. Ocean dispersal of reactor wastes, meeting at Woods Hole Oceano- graphic Institution, Woods Hole, Mass., August 5-6. HOLLAND, H. D., and J. L. KULP. 1952. The distribution of uranium, ionium and ra- dium in the oceans and in ocean bottom sediments. Lament Geological Observatory Technical Report No. 6. RANKAMA, K., and T. G. SAHAMA. 1950. Geo- chemistry. University of Chicago Press. KRUMHOLZ, L. A. 1954. A summary of find- ings of the ecological survey of White Oak Creek, Roane County, Tenn., 1950-1953. USAEC-ORO 132. LATIMER, W. M. 1952. Oxidation Potentials. Prentice Hall, New York. REVELLE, R., T. R. FOLSOM, E. D. GOLDBERG, and J. D. ISAACS. 1955. Nuclear Science in Oceanography. International Conference on the peaceful uses of atomic energy. A/ conference 8/P/277. Scripps Institution of Oceanography contribution No. 794. SVERDRUP, H. U., M. W. JOHNSON, and R. H. FLEMING. 1942. The Oceans. Prentice Hall, New York. U. S. ATOMIC ENERGY COMMISSION. 1956. Operation TROLL. U. S. Atomic Energy Commission, New York Operations Office, NYO 4656, ed. by J. H. Harley, 37 pp.