10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Sampling Efficiency of PM10 Inlets with Different Impaction Substrates
THI-CUC LE, Krishna Kumar Shukla, Jung-Che Sung, Jia Feng, Ziyi Li, Chuen-Jinn Tsai, National Chiao Tung University
Abstract Number: 324 Working Group: Control and Mitigation
Abstract The EPA louvered PM10 inlet (16.7 L/min) is commonly used in PM10 FRM samplers or FEM monitors. The particle collection efficiency of the PM10 inlet is influenced by the wind speed, particle bounce and particle overloading. To study the effect of wind speeds, the sampling efficiency of PM10 inlet was calculated as the product of the particle collection efficiency of the PM10 impactor determined in our laboratory with the sampling effectiveness of TSP inlet at different wind speeds (Vanderpool et al., 2018). The test results of the particle collection efficiency of the impactor showed the cut-size of 10.29 ± 0.07 µm and sharpness of 1.37 ± 0.03, which are very close to those determined from the sampling efficiency of the PM10 inlet at different wind speeds. The estimated bias in PM10 concentrations at different wind speeds (2, 8, and 24 km/hr) is less than 3.1%, 6.7% and 13.8% as compared to USEPA’s ideal concentrations, and less than -4.9%, -2.8 and 10.4 % as compared to the concentrations calculated by Tolocka et al. (2001), respectively. That is, the measured PM10 is influenced by the wind speed, especially when the wind speed is high. To study the effect of particle overloading, four clean PM10 inlets with grease-coated impaction surface were tested for 5 days sampling. The results showed good comparability (R2 > 0.97) among four inlets. However, the field comparison test of cleaned and uncleaned (not clean daily) PM10 inlets showed that the uncleaned PM10 inlet oversampled PM10 after the first 3-day sampling since particles bounce off from the multiple layers of collected particles on the impaction substrate.
In this research, an oil-soaked glass fiber filter (GFF) supported by an oil-soaked 25-mm porous metal disc was used to replace the grease-coated flat impaction surface of the PM10 impactor to eliminate particle bounce. The laboratory test results showed that the modified PM10 impactor had the same cut-size and sharpness as the original PM10 impactor. The field comparison test of the modified PM10 inlet collocated with cleaned and uncleaned original PM10 inlet is being conducted at National Chiao Tung University, Taiwan. The modified PM10 inlet is expected to eliminate particle overloading during longer sampling period since silicone oil will wick up through the layers of collected particles to reduce particle bounce.