SummaryThe alga Chlorella pyrenoidosa has been grown in mass quantities on 94 at. yo
W02.Neither inhibition nor a requirement for adaptation was encountered; changes in morphology were not evident. A statistically significant increase in mass of cells produced in the presence of W O z was observed.The algal cells have been labeled to the 90 at. % I3C level.
sulfate determinations are given in Table V.Sulfur recoveries of 100% were obtained from sodium sulfite, sodium thiosulfate, and the mineral zinc sulfide concentrate should assure the complete sulfur retention in the nitric-perchloric acid method of oxidation of biological materials.
Literature Cited(1) Assoc. Offic. Agr. Chemists, "Official Methods of Analysis," 8th ed., 1955.
The role of strontium-90 in the biosphere has reached marked prominence within the past decade. It is one of the products of nuclear fission (1); it has been shown to be a possible carcinogenic agent (2); and it has an appreciable half-life. Further, it is a close periodic relative of calcium; its relation to calcium metabolism has been reviewed (2). Libby (3) and others have investigated the problem of strontium-90 fallout and have indicated the importance of the plant in the biological chain of transfer from soil to animal, to milk, and hence to man.Collander (4) in 1937, using milligram amounts of calcium and strontium, showed that lettuce took up 500 times as much calcium as strontium. However, the ratio of calcium to strontium in the nutrient was of the order of 400 to 1. He places calcium and strontium in the same group relative to availability and relates availability to electrical mobility of the ions. If the work of Collander employed nutrient solutions, as is indicated, the results are probably not applicable to soils [see also (5)1.It was the purpose of the investigation discussed here to study the uptake of strontium-90 by plants growing in the presence of known amounts of the radionuclide and controlled concentrations of calcium.
MethodsField tanks were chosen for this study, rather than greenhouse pots, to more nearly duplicate field conditions. Thirty tanks, each 5 by 5 feet and 2 feet deep, were filled to a depth of 18 inches with a soil composited from local 18 DECEMBER 1959 Los Alamos soil, clay, and barnyard manure in the ratio of 4 to 1 to 1. The parent material of local soil is tuff, high in silicious matter and low in organic matter, with a low ion-exchange capacity. To assure uniformity, the separate fractions were passed through a shredder and then combined in the proper proportions and repassed.A final mixing of the soil, radionuclides, and calcium was accomplished in a ?-yard concrete mixer; the radionuclides and calcium, as the chloride, were brought into solution and pumped into the mixer as tumbling was taking place. The use of calcium chloride was indicated because preliminary laboratory experiments had shown that calcium carbonate would not be available to the plant in this soil. Uniformity of distribution was determined by an analysis for leachable chloride, on the assumption that even distribution of calcium chloride indicated even distribution of the added radionuclides. The average variation among 90 random samples was less than 1 percent.The concentration of strontium-90 and cesium-137 was such that 50 counts per minute per gram of soil were obtained. Preliminary calculations indicated that this level of activity would yield crop samples with satisfactory counting statistics. The amount of calcium chloride was varied from 1.5 to 18.1 milligrams of calcium per gram of soil in five increments. The intrinsic available calcium concentration of the mixture was 1.5 milligrams per gram of soil, and this level served as the control.In addition, one tank received 1.5 milligrams of ca...
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