Yu-Mei Huang1, Sheng-Hsiu Huang1, Chih-Wei Lin This email address is being protected from spambots. You need JavaScript enabled to view it.1, Hsi-Hsien Yang2, Chih-Chieh Chen1

 

1 Institute of Environmental and Occupational Health Science, College of Public Health, National Taiwan University, Taipei 10055, Taiwan
2 Department of Environmental Engineering and Management, Chaoyang University of Technology, Taichung 41349, Taiwan


Received: April 13, 2020
Revised: July 3, 2020
Accepted: July 31, 2020

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.


Download Citation: ||https://doi.org/10.4209/aaqr.2020.04.0149  

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Cite this article:

Huang, Y.M., Huang, S.H., Lin, C.W., Yang, H.H. and Chen, C.C. (2020). Evaluation of Bias in the Measurement of Condensable Particulate Matter with Method 202. Aerosol Air Qual. Res. https://doi.org/10.4209/aaqr.2020.04.0149


HIGHLIGHTS

  • The positive and negative measurement biases were evaluated in this study.
  • The SO2 artifact in the water during the sampling cannot not be avoided.
  • The leakage between the filter pater and the filter holder can be reduced.
  • The force ventilation method can reduce the drying time from 100 h to 2.5 h.
 

ABSTRACT


In the present study, positive and negative biases when measuring condensable particulate matter (CPM) was measured according to US EPA Method 202. Four factors were considered to measure and improve CPM overestimation: SO2 absorption, the volume of condensate, oxygen content, and residence time. Negative biases were evaluated using weight loss caused by static electricity, vapor pressure of the particles, rinsing volume, beaker size, and filter paper holder. Finally, a forced ventilation chamber was designed to reduce the drying time of the organic sample. The results revealed that artifacts produced by SO2 could not be eliminated. The homemade condensate-divert impinger did not reduce the amount of artifacts because the oxidation of SO2 already occurred when it came into contact with water while passing through the Graham condenser. The residence time, volume of condensate, and oxygen content can all increase CPM overestimation. Therefore, field sampling should be performed as quickly as possible. Furthermore, electrostatic neutralization of the beaker should be performed before weighing it. Because of the high volatility of the material with high vapor pressure, nitrogen purging may reduce the particle mass with high vapor pressure. Furthermore, when the CPM sample was transferred from the beaker to the tin, a smaller beaker size led to lower residual mass. A 4% particle loss was measured according to the leakage of particles between the filter paper and the filter paper holder provided by the original manufacturer. A gasket is therefore recommended to minimize leakage. Finally, it took only 1.5–2.5 h for the organic sample to dry when it was placed in the forced ventilation chamber, and a sample recovery rate of >98.5% was achieved.  Although the artifact produced by SO2 is unavoidable, estimation of PM2.5 can be more precise by considering our proposed improvements.


Keywords: Condensable particulate matter; SO2 artifact; Method 202; Stack sampling.



Aerosol Air Qual. Res. 20 :-. https://doi.org/10.4209/aaqr.2020.04.0149  


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