[en] A modified version of J.A. Leary's autoradiographic technique utilizing nuclear emulsion plates, was used to obtain abundance of, and equivalent size distributions for, plutonium particles in Rocky Flats surface soil. A total of 1700 particles were sized, for which mean ²³⁹Pu0₂ equivalent diameters of 0.29, 0.25 and 0.20 μm were found for exposures of soil for varying times to emulsion plates. Uncertainties associated with values necessary to extrapolate to actual diameters were considered. A method to scan for particles greater than 1.50-μm equivalent diameter, utilizing X-ray film, was also used. The largest particle sized with this procedure was 6.86-μm ²³⁹Pu0₂ equivalent diameter, which would not be of sufficient magnitude alone to account for elevated plutonium activity observed previously in several Rocky flats surface soil samples. Variability in particle concentrations was observed, however, which suggested that a heterogeneity in the spatial distribution of plutonium particles in the soil may partially explain observed variability in soil plutonium concentrations. (author)