SUBMICROMETER AEROSOL MASS DISTRIBUTIONS OF EMISSIONS FROM BOILERS, FIREPLACES, AUTOMOBILES, DIESEL TRUCKS, AND MEAT-COOKING OPERATIONS

An electrical aerosol analyzer was used to measure the submicrometer aerosol size distributions of emissions from many of the important combustion sources found in urban areas. A dilution stack sampling system was used to provide a common basis for collection of the exhaust, and to cool and dilute the source emissions prior to measurement. The submicrometer aerosol mass distributions observed for these combustion sources are in some cases unimodal, and in some cases bimodal. The bimodal mass distributions suggest the existence of a nucleation mode and a larger mode within the fine particle primary aerosol mass distribution. Growth of the larger mode was observed with increasing residence time in the dilution sampler. The predominant peak in the mass distribution emitted from each source measured in this study occurs at or below about 0.2-mu-m in particle diameter, whereas the Los Angeles atmospheric aerosol contains peaks at a variety of sizes in the range between 0.1 and 1.0-mu-m in particle diameter, including peaks at sizes larger than 0.2-mu-m. This suggests that considerable modification of the primary aerosol size distribution occurs because of subsequent processes in the atmosphere. The data presented here are intended for use in defining the size distribution of the primary combustion source effluent for use with mathematical models of the evolution of the atmospheric aerosol size distribution.