Gross Beta Radioactivity of the Algae at Eniwetok Atoll, 1954-1956 (Deleted)

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GROSS BETA RADIOACTIVITYOFTHEALGAE Laboratory of Radiation Biology University of Washington UNITED STATES ATOMIC ENERGY COMMISSION Technical Informatfon Service

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Thin report wae prepared ee an account of Government rponeored work. Neither Uw Unlted States. *or the Commlrrlon. nor *ny perron acting on bebrlf of the Commlrrlon: A. Makes eny warranty or reprerentation, expreered or implied, with rerpect to the eccurscy. completeneer. or urefulneee of the lnformatlon contained in thir report, or that the us0 of any information, spparatur, method, or procere dircloeed in tbie report mxy not l&Me privately owned rlghte; or B. Areumee any llabllltlee with rerpect to the use of, or for danugee rerultiz# from the ure of any lnformatlon. apparatue, method, or procerr dieclored in thle report. Ae used in the above, “pereon acting on bebali of the Commlrrlon” lncludee any employee or contractor of the Commlrrion , or employee of luch contractor. to the extent that ruch employee or contractor of the Commleelon, or employee of ruch contractor preparer. dleeemlnatee. or provider acceoe to, xny information purrrunt to hlr employment or contrwt with the Commlerlon. or hir employment with ruch contractor. This report has been reproduced directly from the best Printed in USA. Price $1.00. Available from the Office of Technical Services, Department of Commerce, Washington Gross beta &dloactlvlty of the algae at Enlwetok Atoll, Gross beta radioactivity of the algae at Eniwetok *toll, 1954-

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GROSS BETA RADIOACTIVITY OF THE ALGAE AT ENIWETOK ATOLL, Laboratory of Radiation Biology University of Washington Operated by the University of Washington under Contract No. AT( 45- 1) 540 with the United States Atomic Energy Commission

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A study was made to determine the amounts of radioactivity in marine algae, water and lagoon bottom sand collected at Eniwetok Atoll during the period April 1954 to April 1956. The highest levels of beta radioactivity of algae collected after the detonation of a nuclear device (Nectar) were in algae from those islands closest to the site of detonation and in the downwind path of the fallout. With time after detonation, the decline of radioactivity in the algae at Belle I eland was faster than can be accounted for on the basis of physical In March 1955, algae and bottom sand collected in the deeper waters ( 20 to 140 feet) of the lagoon, one half to two miles offshore, contained as much or more radioactivity than samples collected in the shallow water near shore. The radioactive decay rates of algae samples collected from Leroy and Henry Islands were greater than those of algae from other islands, indicating that there was less residual contamination from previous detonations at these two islands. Study of the radioactive decay rates of the algae at Belle Island showed that the radioactivity was decaying at a relatively low rate, which became slower with samples collected late in the survey. These observations indicate that the longer-ltved isotopes were being taken up by the algae.

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GROSS BETA RADIOACTIVITY OF THE ALGAE AT ENIWETOK ATOLL, Since the Operation Crossroads tests at Bikini Atoll in 1946, the Laboratory of Radiation Biology, University of Washington, has been investigating the effects of radiations released by nuclear detonations upon living organisms. The amounts of radioactivity detected in aquatic and terrestrial organisms and the effects of the nuclear detonations on these organisms were studied in 1946 , 1944 2), i 948( 3), 194d4’ , and 1952( 5’ . These studies took place either shortly after a detonation or at a later date, often as much as a year or more after a nuclear test. Thus, there were gaps in the knowledge of the interim periods. Consequently, a series of investigations was initiated by this Laboratory, in which a year’s continuous study was made of the effects of nuclear detonations on biological organisms. This study was done in conjunction with the 1954 weapons tests at the Eniwetok Test Site. The results of the investigations on the following organisms have already been reported: The study of the marine algae constituted an integral part of this program. The main objectives were to determine the rate of decline of radioactivity of several genera of algae and to determine whether these

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algae were selectively absorbing fission products released by the nuclear detonations. Other objectives were to determine the geographical distribution of radioactivity and to determine the variability in the levels of radioactivity in the same species. The following collections of algae were made: (1) samples of several genera of algae and of sea water from the intertidal zones at Belle Island (Fig. 1) at varying intervals of time before and after a nuclear detonation on an adjacent island; (2) samples of three genera of algae in the shallow water near eight other islands of the atoll at approximately monthly intervals; (3) samples of algae and bottom sand from the deeper waters of the lagoon off seven islands. The samples were prepared at the Eniwetok Marine Biological Laboratory for further processing at the Laboratory of Radiation Biology, University of Washington, Seattle. The samples of algae were dry ashed for counting in an internal gas-flow counting chamber. The methods used in the preparation of samples for radioassay are described in this Laboratory’s report, UWFL-43 (7) and the procedures for counting are outlined in WF616(5) (UWFL-33). The samples of sea water were placed on 1 l/a-inch stainless steel planchets and dried under an infrared lamp

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Fig. 1. Eniwetok Atoll showing the islands where collections were made, April 1954 to April 1956.

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before counting. The eamplee of bottom sand were dried in an oven at 96’ C, and lOO-mg portions of the dried material were spread on a planchet and dry ashed before counting. The counts of radioactivity were corrected to the date of collection; the factors used to correct for radioactive decay (decay factor) for all but three of the samples were based on a soil sample collected on May 15, 1954,at Belle Island. For the early collections decay factors as high as 16. 2 were used, whereas for the last collection a decay factor of only 1. 02 was applied. Corrections aleo were made for self-absorption, backscatter ( 0.771, geometry ( 2. OO), and coincidence for those samples used in determining absolute amounts of radioactivity. Only the correction factor for coincidence was applied to samples used for determining The amounts of radioactivity are expressed in microcuriee per kilogram (UC /kg) of wet tissue for the algae samyiee, in MC/kg of dry matter for the sand samples, and in disintegrations per minute per mill iliter (d/m/ml) for the water samples. The rates of radioactive decay of individual samples of algae, sand, and water were determined by counting the samples on at least three diff erent dates. The decay of mixed fission products approximates a linear log-log relationship for the period involved in this study (10) .

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The rate of decline of radioactivity in some biological sample6 from Rongelap Atoll also has been observed to follow a similar pattern . Therefore, the decay and decline slopes were plotted logarithmically. Studies at Belle Ieland A. Rate of Decline of Radioactivity in the Algae In order to determine the levels of radioactivity in several genera of algae during the period from April 1954 to April 1956, samples were collected on thirty- six different dates, three of these before the test of May 14, 1954. The results of these surveys are summarized in Table 1, and a log-log presentation of the average decline in radioactivity is ill ustrated in Figure 2. The values plotted are based on the average of seventeen samples for each date after May 14, 1954. The individual rates of decline for representatives of six genera of algae (Halimeda, Caulerpa, Spyridia, Dictyota, Lyngbya, and Udotea) were found to be approximately The radioactivity in the samples collected before May 14, 1954 ,was due to the residual radioactivity of the 1952 test series at Eniwetok Atoll (Operation Castle) plus some airborne contamination from the early tests

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Table 1. Radioactivity of the algae at Bogombogo Island (Belle) April 1954 to April 1956 expressed in PC/kg of Date Halimeda Dictyota Caulerpa Lyngbya Spyridia Udotea Codium Microdictyon Miscellaneous 1. Rhipilia 2. Asparagopsis 3. Enteromorpha- 4. Bryopsis

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Date Halimeda Dictyota Caulerpa Lyngbya Spyridia Udotea Codium Microdictyon Miscellaneous 1. Rhipilia 3. Enteromorpha 4. Bryopsis 5. Die tyosphaeria 6. Jania 7. Valonia 8. Liagora

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__ Pre Nectar level Days after May 14, 1954 Fig. 2. Rate of decline of radioactivity of the algae at Belle Island, Eniwetok Atoll,from May 15, 1954 to April

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of the 1954 series at Bikini Atoll. The levels of radioactivity of the algae immediately following the test averaged 2, 500 MC/kg of wet tissue I but declined rapidly, thus the level from previous experiments (1.9 MC/kg) was reached in about 170 days. At the conclusion of the study in April 1956, the average level was 0. 10 MC/kg of wet tissue. The trend for the period was one of general decline of radioactivity, although there was some deviation from this pattern. B. Rate of Decline of Radioactivity in the Sea Water The amounts of radioactivity in the sea water collected in :;le same area as the algae are given in Table 2. In recording the results of the radioactivity in the water, the data are reported in .d/m/ml instead of PC/kg because of the very low levels found. On the first day after the test, the radioactivity in the water averaged 2, 200 d/m/ml but it declined rapidly, so that on the last collection dates it was indistinguishable from the background level. A logarithmic plot of the decline in radioactivity is shown in Figure 3, and it can be seen that the rate is approximately the same as that for the algae, even though the levels in the algae were approximately one thousand times greater. From May 15, 1954 to May 19, 1954, the ratio of radioactivity in the algae to that in the water increased from 2, 500 to 14, 000, which indicates that the algae were concentrating radioactive material even though

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Table 2. Average radioactivity of intertidal water at Belle Island, Eniwetok Atoll, May 15, 1954 to April 26, 1956, expressed in d/m/l 2 0.95 counting error.

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Days after May 14, 1954 Fig. 3. Rate of decline of radioactivity of the intertidal water at Belle bland, Eniwetok Atoll, from May 15, 1954 to

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the supply was diminishing. c. Geographical Distribution of Radioactivity in the Algae I nter tidal zone. The average levels of radioactivity of of three genera of algae, Caulerpa, Lyngbya, and Halimeda, in the intertidal zones of eight islands of the atoll at intervals 1954 to April 1956 are given in Table 3. Before May 14, 1954, the highest levels were found in algae samples from Vera Island (35 PC/kg) and Olive Island (21 MC/kg), the lowest at ate levels at the other four islands. The rapid radioactive decay in the samples from Vera and Olive Islands and the data from the survey for gamma radioactivity at Vera Island showed that fallout from the March tests at Bikini Atoll had contaminated this area of the atoll. After May 14, 1954, the highest initial values were found in the algae Leroy I sland and the lowest in those from Elmer Island. The levels of radioactivity in the algae from the northern half of the atoll were ally higher than those from the southern islands. Over the period study this pattern remained much the same. The levels of radioactivity of the algae collected at Belle Island were similar to those collected at Alice Island (one mile away) and Vera Island (ten miles away).

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Table 3. Radioactivity in three species of algae collected at eight islands of Eniwetok Atoll from April 1954 to April 1956, expressed in tic/kg of wet tissue. Date of Island collection Alga Bruce Vera Olive Alice Leroy Henry Elmer Janet

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At Belle Island the amounts of radioactivity in specimens of algae from different areas of the intertidal zone (Fig. 4) collected on the same day were compared. An example is presented in Table 4. Table 4. Gross beta activity of four species of algae collected from different area5 of Belle Island on May 22, 1954. Values are expressed as thousands of d/m/g of wet tissue at time of collection. This table and similar data from other collection dates showed that the radioactivity of the algae from different areas was essentially The variability in the radioactivity of five to ten specimens of Halimeda sp. from the same area was also determined for eighteen collections. The coefficient of variation, C (C = standard deviation mean), varied from 12 to 65 per cent, the average being 35 per cent, an indication of great variability in the amounts of radioactivity in the samples collected from the same area. Similar conclusions were reached

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Inner Coral- Algal Flat Fig. 4. Diagram of Belle Island, Eniwetok Atoll, showing the areas of collection.

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concerning the variability in three collections of H. stuposa, each in-- volving ten portions of the same plant. Deep waters of the lagoon. A summary of the results of the radioactivity of nine deep-water collections of bottom sand and fourteen deepwater collections of algae is given in Table 5. The values of radioactivity for the bottom sand are expressed in pc/kg of dry weight because they are more reliable than those based on wet weight. Consequently, when the radioactivity of the coral sand and algae were compared, conversion factors were applied to the values for the algae to convert them to a dry weight basis. The conversion factors are given in Table 5. The results show that in the southern end of the lagoon (Rex Island) the radioactivity of the algae and bottom sand was high in June 1954, but much lower (in the algae) in August and September, 1954, (Elmer Island) and in March 1955 (Elmer, Glenn, and Leroy Islands). In the northern end of the atoll, however, the levels of radioactivity in the algae and sand were high in March 1955, especially in the vicinity of the detonation (Edna Island). In the lagoon off Janet and Vera Islands the radioactivity of the bottom sand was also high at this time. A comparison of the radioactivities of the deep-water algae and the shallow-water algae is given in Table 6. In three of the four cases where comparisons can be made, the deep-water algae contained higher levels of radioactivity than did the shallow-water algae. Further study would be necessary to determine the consistency of this relationship and to develop

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Table 5. Radioactivity in algae and sand from the deep waters of water depth Date of Halimeda opun tia 1.98 0.20 * Multiplication factors used to convert wet weight to dry wei,rht ** Radioactivity in algae Radioactivity in sand

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water depth Date of * Multiplication factors used to convert wet weight to dry weight ** Radioactivity in algae Radioactivity in sand

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an understanding of the methods of distribution of radioactivity in the Table 6. Gross beta activity of the algae collected from the deep and shallow waters of Eniwetok Atoll, expressed in PC/kg …