Development of a PM 10/PM 2.5 Cascade Impactor and In-Stack Measurements

Combustion and industrial processes are an important source of particles. Due to the new PM 10 and PM 2.5 standards for ambient air quality, a sampling system for PM 10/PM 2.5 in-stack measurements was designed and calibrated. In this new system, the exhaust gas is isokinetically sucked into a two stage impactor through the inlet of a plane filter device and the aerosol is fractionated in the particle size classes >10 w m, 10-2.5 w m, and <2.5 w m. Due to a relatively high volume flow (ca. 3.2 m 3 /h, depending on exhaust gas conditions), sampling times are kept short, e.g., 30 min for dust concentrations of 10 mg/m 3 . The impactor was calibrated in the laboratory and then operated at various industrial plants. Parallel measurements with identical devices showed average standard deviations of 3.1% (PM 10) and 3.4% (PM 2.5). Measurements of the cascade impactor together with the plane filter device gave plausible results and average PMx/TSP ratios of 0.49 (PM 2.5/TSP) and 0.78 (PM 10/TSP), showing a large variability for different processes. Elemental analysis using total-reflection X-ray fluorescence spectrometry, together with the size-fractionated sampling, proved to give characteristic patterns of the emitted aerosols, which can be used for a subsequent fingerprint modelling for source apportionment of ambient air pollution.