A Novel Multifilter PM10-PM2.5 Sampler (MFPPS)

Abstract

A novel multifilter PM10-PM2.5 sampler (MFPPS) that enables the collection of four PM10 and four PM2.5 samples simultaneously has been developed and tested. The MFPPS uses a PM10 impactor as the inlet and operates at 33.4 L/min. After the inlet, the aerosol flow is divided half by a Y-type fitting. Half of the flow is directed into four PM10 filter cassettes, while the other half is directed into four PM2.5 filter cassettes after the aerosols are further classified by a PM2.5 impactor. An active flow control system consisting of two mass flow controllers (MFCs), one for PM10 and the other for PM2.5, is used to fix the total flow rate of 16.7 L/min for four PM10 or four PM2.5 channels based on the ambient pressure and temperature. To ensure flow rate uniformity through each of the four PM10 or four PM2.5 filter cassettes, an orifice is assembled behind each of the filter cassettes to increase the pressure drop, such that the flow rates of eight sampling lines are nearly equal using just two MFCs. The MFPPS was calibrated in the laboratory for particle collection efficiency curves first. Then, the ambient PM concentrations were compared with those of other two collocated FRM samplers, the dichotomous PM10 and the EPA WINS PM2.5 sampler in the field study. Calibration results showed the cutoff aerodynamic diameters of the PM10 and PM2.5 impactors were 9.8 +/- 0.1 and 2.5 +/- 0.05 mu m, respectively. Field comparison results indicated PM10 and PM2.5 concentrations agreed well with the other two PM samplers.