= Results of a study of the passage of radioisotope solutions into water (1.3 gram/liter) at different weight ratios of phases V/m are shown in Figure 22. The passage of strontium 90 at V/m 20 and 200 is practically identical. However, at V/m = 2 the "first treatment' effect disappears; this decreases the value of the solubility coefficient. The behavior of cesium 134 changes considerably as the V/m grows. At V/m 2, cesium is practically undetectable in an aqueous medium; at V/m = 20 the value of the solubility coefficient is the same for successive water treatments, but at V/m = 200, together with an overall increase in its solubility, the passage of cesium 134 into water acquires an exponential relation to the number of treatments. Ruthenium 106 under these conditions behaves similarily to strontium 90. In the case of antimony 125, as the V/m increases, the elution of this isotope from contaminated rock intensifies. In studying the dependence of the value of the passage of radioisotopes into water upon the degree of its mineralization (see Figure 23), it was established that a change in the mineralization of a solution of a calcium, magnesium and sodium chloride mixture within the limits of 0.13 to 13 g/l practically does not affect the degree and nature of radioisotope elution. The passage of radioisotopes from a salt sample into aqueous solution over a wide pH range was studied. The salt was taken from the explosion cavity in the salt bed. These studies were conducted in the period of D+ 60 - 150. The pH values were assigned with the aid of HCl and NaOH solutions. The salt (was treated with) water with an assigned pH value at room temperature for two hours at a phase ratio equal to 60. The results of study of the passage of separate isotopes into aqueous solution under these conditions are shown in Figure 24. It can be seen from these data that the solubility of the radioisotopes is closely associated with their nature and their chemical properties. The solubility of cesium 137 which does not form weakly soluble compounds over a wide range of pH values, is practically independent of the pH and lies within the limits of 80-100%. Isotopes, whose salts hydrolyze with the formation of weakly soluble hydroxides possess a clear dependence of solubility upon the pH of the medium. These include cerium 144, ruthenium 106 and zirconium 95, whose solubility falls sharply beginning with pH = 4-5. In this case, however, ruthenium 106 displays an ability to form complexes, since in the range of pH = 10-12 its solubility is approximately equal to 2%, while the solubility of zirconium 95 and cerium 144 is more than one order lower. Of interest is the behavior of antimony isotopes, whose solubility has a minimum in the range of pH 7. Here the amphoteric properties of antimony are apparently manifested; in the acid range it may be present in the form of 3- or 5-valent cations, and in the alkaline range-in the form of the Sbo- anion, which forms easily soluble compounds with metals of the first group. 3. Secondary branch migration in the throwout region In the crater zone of the "1003" explosion, studies were made of the contamination of the layer of air nearest the ground by radioactive products as a result of secondary dust formation-natural (wind) and artificial-of various types brought about by earth-moving operations and the movement of motor vehicles along the contaminated territory. Experiments were conducted during the summer on three platforms located at various places on the throwout in the crater zone. The dose rate at these platforms was 10-20 mr/hr. The active ground layer at platforms number 1 and 2 was equal to 5-7 cm, and was 2 cm at platform number 3. During the period the operations were conducted, the ground moisture at the platforms varied from 10.6% to 3%, and the wind speed in the surface air layer from 0.6 m/sec to 6 m/sec. The distribution of activity according to particle dimensions in the throwout at all three platforms was near the standard-logarithmic distribution with parameters of A≈ 400 microns, σ ≈ 0.2. Air contamination in all experiments was determined with the aid of filters. The concentration of radioactive products in air (according to beta activity) as a result of natural dust formation during the period the operations were conducted varied within the limits of (1.4-100) × 10-13 Curies/liter. Air contamination depended upon the ground moisture and the wind velocity. Thus, as ground moisture (with the wind constant) decreased from 10.6% to 3%, the concentration of radioactive materials in the air increased approximately by one order. On the other hand, when the ground moisture was constant (3%), and the wind velocity changed from 0.6 m/sec to 5 m/sec, the concentration of radioactive materials in the air increased five times. Particles determining air contamination had dimensions of less than 10 microns, with 40-80% of the activity rising into the air appearing on particles with dimensions of 1 to 10 microns. Air contamination in the case of the movement of motor vehicles along the contaminated area (artificial dust formation) was at one order of magnitude higher, and even more, than in the case of natural dust formation and was (0.5500) × 10-12 Curies/liter. In this case the concentration of radioactive materials in the air depended considerably on ground moisture and was practically independent of wind velocity. Thus, when moisture decreased from 10.6% to 3% (with wind velocity constant), the concentration of radioactive materials increased approximately 10 times; in a period when moisture was practically constant (3%), and wind speed in the surface air layer changed from 0.6 m/sec. to 5 m/sec., the concentration of radioactive materials in the air was also constant. Contamination of the air by radioactive materials was brought about by particles with considerably larger dimensions than in the case of natural dust formation. The activity of dust rising in air was approximately evenly distributed between two fractions (1-10 microns) and (10-100 microns). In the case of motor vehicle movement on a road where the active ground layer had been removed by a bulldozer, air contamination was approximately the same as in the case of natural dust formation. The degree of radioactive air contamination when earth works were conducted in the throwout region was 2-3 times higher than in the case of natural dust formation and was 3-240 × 10-13 Curies/liter. 4. Radioactive contamination of the plant cover in the fallout pattern from an underground nuclear explosion Secondary wind migration and redistribution of radioactive products play an essential role in contamination of the plant cover. Studies were conducted on the content of radioisotopes in the plant cover in the pattern of an underground nuclear cratering explosion in the dry steppe zone. The radioisotopic composition of vegetation differs from the composition of isotopes in the soil, especially in the close-in zone, where the vegetation contains 95Zr and 144Ce isotopes and is enriched with Sr and 106 Ru. The content of radioisotopes in plants depends on the structure of their above-ground organs. Plants with strongly disjointed and rough stem and leaf surfaces are contaminated several times more than plants with smooth leaf surfaces and low surfaces-to-biomass ratios. Thus, the contamination of |