MODELING VERTICAL SPREAD OF AIRBORNE POLLUTANTS FROM SOURCES NEAR GROUND-LEVEL - COMPARISON WITH FIELD-MEASUREMENTS

An extensive set of field data from Project Prairie Grass has been use d to evaluate various methods of estimating the input parameters commo nly used by analytical plume models for characterizing the vertical pr ofiles for wind speed and eddy diffusivity. Estimation of the vertical eddy transfer coefficient using the Businger heat transfer parameters from similarity theory showed the closest agreement with experimental data measured in the near vicinity of the source (<1,000 m downwind). Using the optimal input parameter estimation techniques identified, t he downwind and vertical concentration profiles predicted by four anal ytical models were quantitatively compared with the field data under a range of meteorological conditions. Near ground level in the downwind direction, under stable atmospheric conditions all four models genera ted similar predictions that agreed fairly well with the data. Under u nstable conditions, significant differences in the predictions of the four models were seen, especially at greater distances downward.