SHORT-RANGE ATMOSPHERIC-DISPERSION MEASUREMENTS FROM AN ELEVATED SOURCE

Abstract

Dispersion measurements of a tracer, uranine dye in solution, were made out to two miles from the re- lease point in unstable atmospheres. The tracer was released from the top of a 150-ft tower and sampled at ground level by 100 high-volume air samplers. Some sixteen releases for 30-min periods were analyzed. Techniques of dispersal, collection and analysis of the tracer are included. Meteorological measurements during the tests included vertical- and horizontal-wind-direction fluctuations at several levels on the 150-ft tower and vertical temperature difference. Measured air concentrations agree well with those predicted from a meteorological model using wind- direction variances as dispersion parameters. Prediction equations are also empirically developed for computing the distance to maximum ground-level air concentration and for lateral particle variance to two miles. The measured vertical inhomogeneity of turbulence does not prevent a fair agreement between pre- dicted and measured surface air concentrations when only source-height wind data are used. Since the dispersion parameters were determined at the time of the diffusion experiments, the observed and computed results are not independent. Independent test data were not availabIe for a more rigorous check of the method.