Development and evaluation of an impactor for a PM2.5 speciation sampler

A conventional impactor for a particle speciation sampler was developed and validated through laboratory and field tests. The speciation sampler consi sts of the following components: a PM,, conventional impactor that removes particles larger than 2.5 mum, an all-glass, coated honeycomb diffusion den uder, and a 47-mm filter pack. The speciation sampler can operate at two di fferent sampling rates: 10 and 16.7 L/min. An experimental characterization of the impactor's performance was conducted. The impactor's collection eff iciency was examined as a function of critical design parameters such as Re ynolds number, the distance from the nozzle exit to the impaction plate, an d the impaction substrate coating method. The bounce of particles larger th an the cut point was successfully minimized by using a greased surface as t he impaction substrate. Additionally, a series of field intercomparison exp eriments were conducted at both 10 and 16.7 L/min airflow. PM2.5 mass and S O42- concentrations were measured and compared with the Federal Reference M ethod (FRM) and found to be in good agreement. Results of the laboratory ch amber tests also indicated that the impactor's performance was in good agre ement with the FRM.