Fitting Multimodal Lognormal Size Distributions to Cascade Impactor Data

Abstract

A procedure is described for fitting multimodal lognormal size distributions to cascade impactor data. The method was applied to published cascade impactor measurements for ammonium and nitrate that were previously analyzed by procedures that do not assume a functional form for the size distribution. An evaluation of the lognormal fitting procedure by Monte Carlo simulations demonstrated that unbiased parameters and reliable estimates of their uncertainties require correct specifications of measurement precision and impactor characteristics.