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Michihiko Yatazawa a & Yoshio Yamazaki aa Agricultural Chemical Dept. , Nagoya University , JapanPublished online: 30 Apr 2012.
To cite this article: Michihiko Yatazawa & Yoshio Yamazaki (1956) , Soil Science and Plant Nutrition,2:1, 158-163, DOI: 10.1080/00380768.1956.10431876
To link to this article: http://dx.doi.org/10.1080/00380768.1956.10431876
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ABSORPTION OF FISSION PRODUCTS BY PLANTS (PART 5) ABSORPTION OF GROSS FISSION PRODUCTS
Michihiko Y ATAZA WA and Yoshio YAMAZAKI Agricultural Chemical Dept., Nagoya University
Received January 17. 1957
One of the authors reported in the preceding paperD the absorption by plants of unseparated fission products derived from the H-bomb detonated in Spring of 1954 at Bikini-atoll. Since the authors had, thereafter, some amounts of gr.lss fission products which were waste of atomic pile by courtesy of United States Atomic Energy Commission, they began some experiments on the absorption of the gross fission products by plants.
As a part of the radioiicological study on circu-lation of fission products which have been and will be brought either from atomic bomb explo-sions as fall-out or from atomic piles as radio-active wastes, such experiments may offer some suggestive and useful data for large-scale peaceful utilization of atomic energy through fission in future.
There are several papers on the absorption by plants of chemically separated fission products2-> or radioactive debris19 10> of atomic bomb. This paper deals with the absorption of the radioactive waste of atomic pile by rice, barley, wheat, soy bean, kidney bean, lettuce, egg plant, and tomato.
I. Gross Absorption of Fission Products
1.1 Materials and methods Soil: Anjo sub-soil of clay loam was used.
Chemical characteristics of the soil were as fol-lowi!: pH 5.2, acid soluble Fe203 3.55'G, C 0.6.%, N 0.05!'1G, Si02/Al,03 2.0.
Plants: Following eight species of plants were used: Rice plant (Oryza sativa L.), barley (Hordeum sativum Jessen), wheat (Triticum vulgare Vill), soy bean (Glycine max Merrill), kidney bean (Phaseolus vulgaris L.), lettuce (Lactuca sativa L.), egg plant (Solanum Melon-gena L.), and tomato (Lycopersicon esculentum Mill).
Fission Products: Gross fission products used were obtained fr.lm the Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A. through Japanese Radioisotope Association. These pre-
parations were nitrate in HN03 solutions, so they were neutralized with ammonia before use.
Radio-Assay Method: Plant samples were se-parated into several parts of organs. Each parts were dried in an oven, weighed, and ashed in an electric furnace. The radioassay of the ash was based upon an average of activities of 0.200 gram samples. However, in case that the amount of the sample ash was less ihan 0.2 gram, all of it was used. Radioactivity was measured using a thin mica-window (2.5 mgjcm") G.M. tube. Natural radiation attributed to K 40 was estimated from K content of the ash.
1.2 Variation in uptake of radioactivity by different plant species
Anjo sub-soil was neutralized with calcium carbonate and fertilized with appropriate amounts of ammonium sulfate, superphosphate of lime. and potassium sulfate. Each four hundred grams of the fertilized and mixed soil was mixed with ca 0.1 me of gross fission products and put into a glass beaker. Germinated seeds of eight species of plants were transplanted io the beakers filled with radio-active soil.
Since the surface area of each beaker was about 43 cm2, 3 to 5 plants were transplanted in cases of soybean, kidney-bean, egg-plant and tomato. In cases of other species of plants 12 to 15 seedlings were used.
The beaker for rice plant was always maintained under waterlogged condition, while the others were allowed at field condition and water was supplied preventing drying up during ihe croP3 growing period. Plants were grown five to nine weeks until approximately same amount of dry matter was obtained in each plot.
Harvested plants were separated into tops and roots. Roots were washed thoroughly to remove adhering soil particles. Radio-activities of eight species of plants were shown in Fig. 1.
1.3 Distribution of radioactivity within the plant and the effect of dressing
Three stumps of 44-day seedlings of rice plant were transplanted to each pot (1/50,000 tan) and
ABSORPTION OF FISSION PRODUCTS BY PLANTS (PART 5)
~peeif'tc activity e.p.m ~ plant dry material 1000 3XIO 3000 4000 '.illlO
R- plant ., r.,. c:J -.
llarlo\ .. -..... Tornat" ~ ....
5 10 Ia ~ ~
ConrentratiOfl factor (. :: =~ o~r=~ ) Fig. 1. Variation in uptake of radioactivity
by different plant species
cultivated for 80 days until maturity. The soil in the pots had been neutralized, fertilized as shown in Table 1, and cnnhminated with 0.3 me of gross fission products.
Table 1. Fertilizers Added to Soil (per one pot)
Double Ca plot
2.0 g of CaC03 to neutralize acidity 4.0g of CaCOs
Nutrient plot 12.0 g of CaC03 2.83 g of (NH4),SO, 1.34 g of K 2S04 2.31 g of CaH4(P04) 2
After maturation, plants were harvested and measured of their radioactivities. Results were shown in Fig. 2.
Specific activity (c.p.m./gm day marrer) 0 bO 1110 150 200
Nutnent C!l Double Ca CJ Control
Fig. 2. Distribution of radioactivity within rice plants and effect of dressing.
II. Radioactive Nuclides Absorbed Through Roots
2.1 Classical Inorganic Analysis Leaf-blades and leaf-sheaths of rice plants
grown on radioactive soil contaminated with gross fission products were used as experimental plant materials. They were ashed and then analyzed in the ordinary method'" with carriers of Sr-nitrate, Zn-chloride and Ferric chloride.
t.eaf-hlades LeaC-aheaths Orieinal G F.P. 211 40 GO"-' 20 40 00?' 20
Vol. 2 SOIL AND PLANT FOOD 195G
02 N HCI , 06';4 Oxabr ....
.. 110 '"'
It N HM tltl Oa&IM .... "' NH..cftnle (pll .. n
b Raoi1'*hvt ,.._.t, Ia roou
ux"" nr l 01" OQiie l acid
... r kl .. -.:tv lnlntl 111 G r P ""
I' NK..Cltrate (pH 41)
5,. NH..citnlO (pH Ill
"' ... Fr'MUcMIIIUII!ler 0
Fig. 4. Elution curves of radioactive elements.
daughter of alkaline earths, were recovered in the form of hydroxides and alkaline earths as carbonates. Distribution of radiation energy in these two fractions was examined as soon as possible after separation.
From the absorption curve, the range of #-particles was determined by Feather analysis. Maximum energy of #-ray was deduced from the following range-energy relations m.
R:::0.542Emu-0.133 when E,uax>O.SMeV R:::0.407 E:,~ when 0.15 MeV using four crops (bean, barley, tomato, and russian thistle)
ABSORPTION OF FISSION PRODUCTS BY PLANTS (PART 6)
and by K.H. Larson et al. 10> using ten crops (kaffir, milo, corn, peas, cauliflower, lettuce, wheat, barley, radish, and ladino clover). In the latter case little differences in ability of uptake by plants were observed. As shown in Table 1, it is clear that solanaceae and leguminosae were being placed in heigher situation regarding to the concentration factor in tops under the experiment-al condition. In addition, it is important to note that the concentration factor in tops of rice plants was the lowest. These results are similar to those of J.W. Nee! et al.4> who examined up-take of Sr90 by several kinds of plant species.
As regard to uptake of gross fission products by roots, the greatest value was obtained in leguminosae, and the concentration factor ex-ceded 20. Because the smallest was observed in solanaceae, the translocation ratio from roots to tops was largest in this species. Rice plants, on the other hand, showed the smallest translocation ratio of about a thirtieth.
Examining the effect of dressing on uptake of fission products, Selders et al. 9> reported that the effect is apparently positive in the increase in gross absorption and in elevation of concentra-tion factor. The present results on rice plants shown in Fig. 2, on the contrary, revealed that concentration factor of radioactive elements decreased inverse-proportionally to the favourable growth. The reasons of this response of dressing may be due to the competitionw in absorption by calc with radioactive alkaline earths, decrease of solubility of radioactive materials by addition of calc, and fixation of radioactive rare earths by fertilizer anion, especially phosphoric acid. The similar results were obtained by the authors in the other investigation on the effect of dressing to uptake of radioactive strontium 1 ~>.
The distribution of gross fission products in rice plant is simillar to that of strontium16>. The specific activity was rather high in leaf-sheaths and in leaf-blades and was lowest in matured grain. Thus, it is unlikely that absorbed fission products can move freely in the plant.
As shown in Fig. 3, it is clear that alkaline earths were selectively absorbed. Most parts of the radioactivity of alkali metal group must be attributed to K40, however, the activity depending on Cs117 cannot be neglected.
To make clear these points, a cabbage plant was cultured in Hoagland's solution contaminated with greater amount of radioactive fission pro-duets. Radioactive elements in the harvested plant were analyzed in the use of ion exchanger
as shown in Fig. 4. These results also reconfirm the selective absorption of alkaline earths by plant, and well coincide with that of the writers previous investigationsll.
Characteristic relationships which are common in the absorption of fission products by plants are: 1) There is greater uptake of rare earths by roots, 2) There is comparatively meager trans-location to shoots, and 3) There is selective translocation of alkaline earths to top.
To identify radioactive elements in this frac-tion of alkaline earths, half-lives and maximum energies of these I' particles were measured. As shown in Fig. 5 to 7, satisfactory results indicat-ing presence of Sr89 and Sr90 were obtained. Used preparation of gross fission products were so aged that it could be expected small amounts of radioactive Ba140 were present. In fact Ba fraction precipitated as chromate from acetic buffer solution of alkaline earths fraction scarcely showed radioactivity. Accordingly consideration about the presences of Ba and La in Fig. 6 were omitted. Measurements of Fig. 5 were made within a few hours after separation. So the I' activity attributed to Y90 in this strontium fraction was restricted within a few percent of the total I' activity. From these reasons Sr9 and
< Feather analysis
l "'""" " eoo c e 200 ..........
0 0.6 1.0
Fraction of range
Total AI aboorber (ms:~em')
Fig. 6. Aluminum absorption curve of Sr fraction,
Vol. 2 SOIL AND PLANT FOOD 1956
lt. < Feather anal)'U
~i:j~ I. l.OOO 05 10 < Fractwm or ranp
Fig. 6. Aluminum absorption curve of Y fraction.
Fig. 7. Decay curve of Y fraction.
Sr90 could be identified from Fig. 5, 6, ar.d 7. Thus it has been made clear that radioactive
strontium are selectively absorbed by plants from soil contaminated with fission products and/or radioactive wastes from atomic pile. Since radio-active strontiums (Sr89 and Sr!IO) are seriously hazardous elements when taken into animal body, the results shown above are very important for human beings considering soil-plant system. Effort must be done to prevent the free entrance of such hazardous elements into human environment. Moreover, one must prepare appropriate means to repress the absorption of radioactive stron-
tiums from soil by plants and must always in-spect the level of radioactive strontiums con-taminating human environment.
The uptake of radioactive wastes from atomit! pile by 8 species of plant.s were studied. The results obtained were as follows:
1) Considerable variation in uptake was as-sociated with the 8 crops considered. The con-centration factor in tops decreased in the order:
Leguminosae, Solaneceae>Compositae >Gramineae
On the other hand, that in roots were: Leguminosae > Gramineae, Compositae
>Solanaceae. 2) Addition of fertilizers and calc considerably
repressed the uptake of fission products by rice plant.
3) The distribution of gross fission products in rice plant was simillar to that of strontium. The specific activity was rather high in leaf-blade and was lowest in matured grain.
4) Chemical analysis of absorbed radioactive elements revealed the selective absorption of alkalin...