X-ray diffraction results showed, as expected, that the fallout samples contained essentially the same minerals as the soil on or over which the devices were detonated. Single selected particles from coral shots showed mostly CaO, Ca(QOH)9, CaCO3. Selected particles from tower shots on alluvium showed the presence of magnetite, Fe30,, but were mostly vitreous. The density of particles from airbursts has been found to be between 3.25 and 5.0 g/cm, with most values lying between 3.5 and 4.0 g/cm’. Particles from surface and near-surface bursts have densities close to those of the soil rocks, with the exception of most of the particles that had been completely fused and that contain primarily device materials. These latter particles have densities greater than 3 g/cm3. Some high-density particles which have been confirmed as mixtures of uranium and plutonium have been observed in Roller Coaster. Spectrochemical analyses were at best semiquantitative. Most analyses were done on selected single particles from a few shots. The results show some minor differences in composition with the substrate (soil with or without a tower). These differences are usually readily explainable. Magnetism. Magnetic (ferromagnetic) particles were found in a number of tower and ground-surface shots. This magnetism could usually be traced to significant amounts of iron having been present in the shot environment as additions (tower, e.g.). No quantitative measurements were made. It was noted, however, that dark particles were generally more magnetic than light particles. These particles were also found to be highly radioactive. Petrographic examination of thin sections from selected particles showed a variety of structures that can readily be explained on the basis of the phenomenology of the events: partial fusion, total fusion, incorporation of Many of these methods were applied to individual particles as well as to representative sample aliquots. The work is generally quite time-consuming and has, therefore, been somewhat limited. Also, fallout from coral shots has been more extensively investigated than fallout from alluvium (NTS) shots. 238 (in the case of coral shots), Most electron microprobe analyses were done on particles from airbursts. Few fallout particles were thus analyzed. Large particles were sectioned and scanned over a cross section. A few selected particles from Area 13 were analyzed intact (Schulz et al., 1975). It is noted that by this method only the surface and subsurface regions of particles are analyzed. Chemical Composition. The chemical nature of fallout and cloud particulates is greatly dependent upon the environmental shot conditions. The methods that were employed included X-ray diffraction, emission spectroscopy, wet chemistry, dissolution, and atomic absorption Spectroscopy, but also the application of the petrographic microscope to thin sections. The electron microprobe analyzer has been used rarely for particulates from shots yielding significant fallout. More recently, the ion microprobe and scanning electron microscope have been added as an analytical tool for particles. some chemical alteration Quantitative chemical analysis was mostly concerned with the iron and lead content of the particles. Other analyses performed were moisture and organic matter. In the case of fallout from coral shots, significant amounts of water were often found in the collectors, and chemical and radtochemical analyses and measurements were performed on all phases. These analyses included some or all of the following: Ca, Na, K, Cl, Mg, Fe, Cu, Al, Si, and U. Isotopic Abundances. Isotopic abundances of the uranium and plutonium isotopes have been extensively measured in both aggregates and individual particles by single- and double-focussing mass spectrometric methods. This has proven to be a powerful tool for identifying the origin within the device of the particle. The activity in determining this property decreased considerably after the late 1950s for particulates from all but free airbursts. Since then, a number of cloud samples from surface and near-surface bursts were analyzed for major constituents for the purpose of reconstructing a sample weight so that radionuclide specific abundances could be calculated. Compositions thus obtained included the contributions from unaltered, inactive soil particles drawn into the cloud. fine grains, and so forth. Sometimes autoradiography was used to locate radioactive regions within a particle. Electrostatic. Early experiments in operation Fitz William attempted to identify particles by their electrostatic charge resulting from their radioactivity. Electrophoretic separation of particles was done by this laboratory in a liquid with the observation that the particles both positively and negatively charged were found. 10 Solubility. Of particular importance to hazards assessment is the availability of radionuclides in debris and in fallout to the biosphere other than through self-implantation of particles. Thus, radionuclides may become available through solubilization, and experiments with different fallout samples have been conducted to determine the solubility of radionuclides. Effectively, however, these experiments are leaching experiments. The value of these experiments is very difficult to assess. The leachability depends on the distribution of the radionuclides in and on the particles, on the properties of the particles, and on the chemical form of the nuclides, therefore often also on the particle size, but in particular, the leachability depends on the leaching liquid. Therefore, regardless which liquid is used in laboratory experiments, often there remains a problem of translating the laboratory results to the “real world." In general, there are two primary phenomena to be considered. One phenomenon is the solubilization of radionuclides in the soil, perhaps followed by the movement of solubilized material through the soil. This solubilization would occur in an environment created by rainwater and the interaction of 239