Radioactivity and Recovery of the Land Plants at Eniwetok Atoll, 1954

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Biology and Medicine RADIOACTIVITY AND RECOVERY OF THE LAND PLANTS AT ENIWETOK ATOLL, 1954-1957 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 long-term investigation was conducted at Eniwetok Atoll during 1954-1957 to determine the rate of recovery of land plants damaged by the radiation, shock and heat blast of the Nectar detonation in 1954. During this period the levels of gross beta radioactivity in the plants, the radioisotopes present in some of the plants and the soil, and the changes in the levels of beta radioactivity in the tissues of the plants, with time after the detonation (decline of radioactivity), also were investigated. At Belle Island eeytin plant species were tagged, measured and photographed before the detonation. At approximately monthly intervals of ten months, and again plants were observed and of recovery was observed after the detonation, for a period after an interval of six months, the photographed. The first indication on the eighth day, at which time buds were noticeable on stems of Scaevola and Messerschmidia plants. In a mOnthIs time, most of the plants had formed new leaves and some had produced flowers and fruits. In six months, the general condition of the vegetation was similar to that which existed before the detonation. Two plants,

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Guettarda and Portulaca, which were unhealthy at ten months, had improved by the sixteenth month. Photographs of the recovery of some of the plants are included In this report, as well as a discussion of agents other than radiation which have been reported to cause similar damage to plants of the coral atolls of the Pacific Ocean.

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RADIOACTIVITY AND RECOVERY OF THE LAND PLANTS AT ENIWETOK ATOLL, 1954-1957 Since the summer of 1946, the Laboratory of Radiation Biology of the University of Washington has conducted studies at the Eniwetok Proving Ground to evaluate the distribution of radioactivity in aquatic and terrestrial organisms of the atolls of the western Pacific and adjacent areas. These studies were made either shortly after a nuclear device had been detonated or after intervening periods varying from several to many months. The results of the investigations conindicated the need for a study of the reinvasion or regrowth of organisms in an area contaminated by radiation, as well as a study of the decline of radioactivity in these organisms (changes in the amount of radioactivity of samples collected at various times). A study of this nature was undertaken following the Nectar detonation at Eniwetok Atoll in the spring of 1954. Facilities were made available at the Eniwetok Marine Biological Laboratory on Elmer (Parry) Island by the Division of Biology and Medicine of the United States Atomic Energy Commission, and logistic support to carry out the sampling program was furnished by Joint Task Force Seven of Operation Castle.

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RADIOACTIVITY AND RECOVERY OF THE LAND PLANTS AT ENIWETOK ATOLL, 1954-1957 Since the summer of 1946, the Laboratory of Radiation Biology of the University of Washington has conducted studies at the Eniwetok Proving Ground to evaluate the distribution of radioactivity in aquatic and terrestrial organisms of the atolls of the western Pacific and adjacent areas. These studies were made either shortly after a nuclear device had been detonated or after intervening periods varying from several to many months. The results of the investigations indicated the need for a study of the reinvasion or regrowth of organisms in an area contaminated by radiation, as well as a study of the decline of radioactivity in these organisms (changes in the amount of radioactivity of samples collected at various times). A study of this nature was undertaken following the detonation of an atomic device (Nectar) at Eniwetok Atoll in the spring of 1954. Facilities were made available at the Eniwetok Marine Biological Laboratory on Elmer (Parry) Island by the Division of Biology and Medicine of the United States Atomic Energy Commission, and logistic support to carry out the sampling program was furnished by Joint Task Force Seven of Operation Castle.

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The study of the land plants was a part of the over-all program of the Laboratory of Radiation Biology. In this report only the results of this portion of the program are presented. The results of the investigations on the following organisms already have been reported: reef fish(24), land The main objective of the land plant program was to determine the length of time required for a plant damaged by a nuclear detonation to resume its normal functions of growth and reproduction while being subjected to chronic radiation. Other objectives were to determine (1) the rate of decline of beta radioactivity In the tissues of land plants growing in radioactive soil during the period starting shortly after detonation of a nuclear device (Nectar) and ending eighteen months later: (2) the gross beta radioactivity of the land plants at several islands of Eniwetok Atoll, and (3) the uptake by the plants of specific radioisotopes from the soil. The main site of study was Belle Island, 2.7 miles E-SE of the detonation (Fig. 1). This area was estimated to be far enough removed from ground zero that the plants would not be uprooted by physical forces yet would have taken up sufficient radioactivity for the proposed study. Other islands

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included in this study also are shown in Figure 1; the code names of the islands are in parentheses. In 1956 another series of nuclear tests (Operation Redwing) was conducted at Eniwetok Atoll. During this series, plant samples were collected from various islands of the atoll as well as in July 1957, one year later. The gross beta radioactivity of these samples is presented in the Appendix Table B. The results of gamma spectrum analyses for specific radioisotopes present in some of the samples collected in 1956 were reported in 1957 by Inwman, Palumbo and South (16) . The beach magnolia (Scaevola sp.*) was chosen as the principle plant for study because of its widespread occurrence in the central Pacific Islands; six other species also were studied. In order to establish the levels of radioactive contamination from previous tests, samples of plant tissues were collected before the detonation. The plants were staked, labelled, measured and photographed. After the detonation, observations and measurements were made of the plants and photographs were taken. Samples to be used for the determination of radioactivity were taken at approximately monthly

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intervals starting on May 22, 1954 and continuing to March 1955. The locations of these plants on the island, which was divided arbitrarily into areas A, B, At each collection period at Belle Island, six subsamples of the top two inches of soil near the base of Scaevola plant No. 1319 were combined and an aliguot of the combined sample was taken for the measurement of gross beta radioactivity. Gamma survey-meter readings also were taken to determine the gamma dose to which the plants were on ice and the plant samples were collected they were put taken to the Eniwetok Marine Biological where they were dissected, weighed, dried, and packaged and later sent to the Laboratory of Radiation Biology in Seattle, Washington; for further processing as outlined in UWFL-33 . The samples were dry-ashed in a muffle furnace at 540°C and counted in an internal gasflow counting chamber. Corrections were made in the counts for geometry, backscatter, coincidence, self-absorption and decay. All counts for the 1954-1955 and April 1956 samples were corrected to the date of collection, the decay factors being based on a soil sample collected May 15, 1954 at Belle Island. For the early collections decay factors as

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SCALE: I INCH * 450 FEET 1216 Guettarda speciosa 1207 Boerhaavia tetrandra 1408 Messerschmidia arqentea 1208 Triumfetta procumbens 1410 Lepturus repens 1211 Portulaca oleracea Figure 2. Diagram of Belle Island, Eniwetok Atoll, showing the location of the land plant stations and the collecting areas.

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high as 16.2 were used, whereas for the last collection a decay factor of only 1.02 was used. The counts for the 19561957 samples, which were not corrected for decay, are presented in the appendix tables. The levels of radioactivity for plant tissues other than scorched leaves are based on wet tissue weights: to convert the latter values to a wet weight basis it is necessary to divide them by 6, the approximate dry to wet ratio for this tissue. The values for soils are based on dry weights. All values in the text tables are expressed in &kg; values in the appendix tables are expressed in thousands of d/m/g/. The rate of decline was plotted on a log-log scale because of its similarity to the decay curve of mixed fission The isotopes present in the samples were indicated by the decay curves but in one soil and four plant samples they were specifically identified by radiochemical analysis*.

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Regrowth of the Land Plants at Belle Island The gamma survey-meter readings taken at Belle Island during the period of investigation are given in Table 1 and in Figure 3, which includes the theoretical gamma dose rate according to Miller and Xoeb (17) and the slope for t-1.2 . The accumulated total dose from one minute after the detonation to the end of 200 days was calculated to be approxiBefore the Nectar detonation, the plants on Belle Island were generally green and healthy-looking. A photograph of the general area taken at this time (Fig. 4a) shows the healthy appearance of the vegetation. In some plants there was yellowing of the leaves and necrosis, especially in Scaevola and Guettarda, and some reddening of the tops of the grass, of plants growing The latter symptom is typical of some species in phosphorus-deficient soil, a condition often found on coral atolls and in areas where the top soil has been disturbed or blown away. The Mike detonation of 1952 had removed most of the plants and top soil from Belle Island, resulting in the depletion of some of the elements essential for plant growth. In spite of these deficiencies regrowth of the

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Table 1. Gamma dose rates three feet above ground in milliroentgens per hour at Belle Island, *Early readings taken with a PDR-39 ionization chamber survey meter and later readings with a Juno AEC Model

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Gamma dose rate-Belle Is. Theoretical gama dose rat& Days after May 14, 1954 Figure 3. Gamma dose rates at three feet at Belle Island, Eniwetok Atoll, May 15, 1954 to March 21, 1955, compared with the decay of fission products from the slow neutron

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Recovery of the plants was rapid. Heavy rains occurred on the third day. On the eighth day green buds, 1-3 mm in length, were observed on the stems of Scaevola and Messerschmidia (Fig. 5a) plants. On the thirty-fifth day the shoot leaves were 7 to 15 cm long, covering much of the old stems (Fig. 5b) and giving the plants a green and healthy appearance. By this time many of the other plants had formed new leaves and three species (Portulaca, Triumfetta, and Messerschmidia) had produced new flowers and fruits. The island now had lost its scorched appearance; from the air it looked green rather than brown as it had one month earlier. In August, three months after the detonation, the plants were growing well (Fig. 6) and had produced new flowers. The had grown to maximum size, and some species, such as Boerhaavia leaves of most of the species the branches had grown almost to the pre-Nectar dimensions. This was not the case with the Guettarda and Lepturus plants, which recovered more slowly than the other species. The new growth on the Guettarda plant (No. 1216) consisted of ten small leaves which originated from a new shoot 18 cm tall at the base of the old plant; the Lepturus plant (No. 1410) was a mat of dead tops with some new growth forming at the periphery.

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In six months the general condition of the vegetation (Fig. 7) was similar to that which existed before the Nectar detonation. In March 1955, approximately ten months post Nectar, the plants appeared to be normal, most of them bearing abundant flowers and fruits, healthy, green leaves, and the usual amount of yellow, older leaves. Plant No. 1216 (Guettarda) however, bore curled, distorted, and unNovember 1955, it bore about thirty healthy, green leaves, had increased in height and apparently was completely recovered (Fig. 8b). Plant No. 1211 (Portulaca) bore only a few leaves in March 1955, but when observed in November 1955, it had recovered somewhat, bearing abundant flowers and some green leaves. No other aberrant growth forms were seen in the field observations at Belle Island. At Janet Island, the fasciated stems and the tumorous growths on plants of Ipomoea tuba ob-.- served in 1949 by Biddulph(6) were still present in 1957. The measurements and observations made on one of the plants, Scaevola (No. 1319),during the course of the study are presented in Table 2. Notes for the remainder of the plants are given in Appendix Tables A and B.

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Levels and Decline of Gross Beta Radioactivity at The amount of radioactivity in the samples of Scaevola plant No. 1319 collected during the study is given in Table 3. The amounts for the other species are given in Table 4. The highest amounts of radioactivity, pre-Nectar, were found in the leaves (20 &kg) of a young coconut plant collected in the western part of the island in Area C and in the roots (18 &kg) and tops (13 &kg) of a grass Plant in the same area. The lowest amount was found in the stem (0.35 &kg) of a Messerschmidia plant at the eastern end of In Scaevola, the levels of radioactivity three days post Nectar were higher than the pre-Nectar levels by factors of 500 (leaves) and 30 (stems) (Table 3). The basal leaves of a Scaevola plant in area C contained the highest level (29,000 &kg) of all of the plant samples collected at Eniwetok Atoll during this study. The amounts of radioactivity of eight tissues of Scaevola plant No. 1319 were compared to determine whether some tissues contained more radioactivity than others. In

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Table 3. Gross beta radioactivity of Scaevdla sp., plant No. 1319, at Belle Island, Eniwe tok Atoll, April 14, 1954 to April 26, 1956, expressed in MC/kg of wet tissue at time Scorched* Basal Terminal Shoot Entire Bark Internal Flowers-Fruits

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Collection Leaves Stems date Scorched* Basal Terminal Shoot Entire Bark I nternal Flowers-Fruits ***From several plants including No. 1319

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Table 4. Gross beta radioactivity of six species of land plants collected at Belle Island, Eniwetok Atoll, April 14, 1954 to April 26, 1956 expressed in uc/kg of wet tissue at time of collection. date Scorched* Basal Terminal Shoot Entire Bark Internal Fruits Roots Tops *PC/kg of dry tissue

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Collection Leaves Stems date Scorched* Basal Terminal Shoot Entire Bark I nternal Fruits Roots TODS

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Collection Leaves Stems date Scorched* Basal Terminal Shoot Entire Bark Internal Fruits Roots Tops

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49 of 54 comparisons the scorched leaves contained the highest levels of radioactivity. The chi-square test shows that …