Samples of ash from the 18 May 1980 eruption of Mount St. Helens were collected from several locations in eastern Washington and Montana. The ash was subjected to a variety of analyses to determine its chemical, physical, mineralogical, and biological characteristics. Chemically, the ash samples were of dacitic composition. Particle size data showed bimodal distributions and differed considerably with location. However, all samples contained comparable amounts of particles less than 3.5 micrometers in diameter (respirable fraction). Mineralogically, the samples ranged from almost totally glassy to almost totally crystalline. Crystalline samples were dominated by plagioclase feldspar (andesine) and orthopyroxene (hypersthene), with smaller amounts of titanomagnetite and hornblende. All but one of the samples contained from less than 1 percent to 3 percent free crystalline silica (quartz, trydimite, or cristobalite) in both the bulk samples and 1 to 2 percent in the fractions smaller than 3.5 micrometers. The long-lived natural radionuclide content of the ash was comparable to that of crustal material; however, relatively large concentrations of short-lived radon daughters were present and polonium-210 content was inversely correlated with particle size. In vitro biological tests showed the ash to be nontoxic to alveolar macrophages, which are an important part of the lungs' natural clearance mechanism. On the basis of a substantial body of data that has shown a correlation between macrophage cytotoxicity and fibrogenicity of minerals, the ash is not predicted to be highly fibrogenic.

A study of the behavior and transport by the Columbia River of the eleven radionuclides 46Sc, 51Cr, 54Mn, 58Co, 59F9Fe, 60Co, 65Zn, 95Zr‐96Nb, 106Ru, 124Sb, and 140Ba was carried out in the river reach between Pasco and Vancouver, Washington, during the period January 1964 through January 1965. This study was accomplished by direct counting of water salts and filter samples on a multidimensional gamma‐ray spectrometer and represents the first measurements of the interactions of most of these radionuclides in the river. Through this multiple tracer technique, the specific and relative behaviors of these radionuclides in regard to their sorption by and movement with suspended particulate matter in the Columbia River were determined. Depletion of these radionuclides from the river during transport and the radionuclide inventory in the stream bed for the river reach between Pasco and Vancouver were also estimated.

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The 222 Rn concentration in exhaust air is being measured at underground uranium mines in the Grants, New Mexico area. The objective of the work is to determine relationships between U 3 0 8 production and the mine characteristics and practices relative to 222 Rn emission. Concentrations in the vent air from two mines ranged from 90 nCi/m 3 to 3800 nCi/m 3 during a month of observations. Diurnal radon emission patterns were seen from each mine which were inversely related to barometric pressure. The average diurnal emission patterns on weekends when no mining occurred were very similar to those on weekdays during active mining, indicating that the mining activities had little short-term effect on those radon emissions. The radon emission rate from each mine vent showed a correlation with the associated ventilated surface area and the cumulative tons of U 3 0 8 extracted there and a higher correlation with cumulative tons of ore extracted. Grab samples of vent air collected at 14 additional mines in the Grants area showed radon concentrations from 7 nCi/m 3 to 21,000 nCi/m 3 •

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