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FIELD VALIDATION OF EXPOSURE ASSESSMENT MODELS. VOLUME 2. ANALYSIS
Citation:
Doran, J. AND T. Horst. FIELD VALIDATION OF EXPOSURE ASSESSMENT MODELS. VOLUME 2. ANALYSIS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/3-84/092B.
Description:
This is the second of two volumes describing a series of dual tracer experiments designed to evaluate the PAL-DS model, a Gaussian diffusion model modified to take into account settling and deposition, as well as three other deposition models. In this volume, an analysis of the data summarized in Volume 1 is given. The four models are described, and an evaluation of the performance of each is given. The evaluation is based on an analysis of C sub d/C sub o, the ratio of the crosswind-integrated concentrations of a depositing and nondepositing tracer, respectively, at a height of 1.5 m. The PAL-DS model is found to overestimate this ratio; a corrected source depletion model appears to give significantly better results. A novel method of determining the effective deposition velocity of the depositing tracer, based on a surface depletion approach, is described. A discussion of model sensitivities, experimental design, and the effects of measurement errors on the model evaluation is also given. Experimental uncertainties may well affect the performances of the models, but it is doubtful that their relative performances would be significantly changed. Errors in describing the diffusion meteorology are likely to be more important in predicting depleted concentrations than errors introduced by the choice of a particular deposition model, which are apt to be more systematic.