PLUTONIUM-BEARING PARTICLE STUDIES Isolation of Plutonium-Bearing Particles From the Test Site. M, W. Nathang and F. Francisco. 537 Characteristics of Radioactive Particles in Close-In Fallout. M. W. Nathans. 549 CONTRIBUTED PAPERS Preconcentration of Plutonium Radionuclides From Natural Water. K. M. Wong, V. E. Noshkin, and T. A. Jokela. 583 Alpha-Sensitive Cellulose Nitrate Track Detectors: Applications to tion. R. W. Buddemeter, A. H. Biermann, and C. Gatrousts. Estimation of Expected Value of Environmental Pollutants With Lognormal and Gamma Distributions. G. C. White. 593 wan the Study of Environmental Contamina- 609 Variable 24am Concentration in Soil Uptake and C.R. in Barley Plants. A. Wallace, R. T. Mueller, and #. M. Romney. 629 The Effect of Fasting on the Transit Time of !**ce in the Mouse Gut. d. F. Wetss and H. &. Walburg. 637 Comparison of Soil Sampling Techniques at Rocky Flats. OD. &, Bernhardt, J. D. Bliss, and G. G. Eadte. Preliminary Model of Plutonium Transport by Wind at Trinity Site. A. F. Gallegos. Environmental 645 f 681 Instrumentation for Im Sttu Radionuclide Assay. ZL. E. Brune. iv 697