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  

  • Download: PDF


Cite this article:

Huang, Y.M., Huang, S.H., Lin, C.W., Yang, H.H., Chen, C.C. (2021). Evaluation of Bias in the Measurement of Condensable Particulate Matter with Method 202. Aerosol Air Qual. Res. 21, 200149. 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


The present study evaluated the positive and negative biases in measurements of condensable particulate matter (CPM) conducted according to U.S. EPA Method 202. To reduce the overestimation of CPM, four factors were investigated: the SO2 absorption, condensate volume, oxygen content, and residence time. The underestimation was assessed by examining the weight loss related to the electrostatic charge of the evaporation beaker, vapor pressure of the particles, volume of the rinsing solvent, size of the evaporation beaker, and leakage between the filter paper and its holder. Additionally, we constructed a forced ventilation chamber to decrease the drying time of the sampled CPM’s organic fraction. The results revealed that our homemade condensate-diverting impinger could neither eliminate nor reduce the artifacts produced by SO2, as the SO2 had already oxidized by the time it passed through the Graham condenser and interacted with water. Since the residence time, condensate volume, and oxygen content can all exacerbate the overestimation of CPM, field sampling should be performed as quickly as possible. Furthermore, the evaporation beaker should be electrostatically neutralized prior to its weighing. Nitrogen purging may reduce the mass of the particle fraction possessing high vapor pressure, as these substances are highly volatile. Also, we found that when we used a smaller beaker, less residual mass remained in it after transferring the CPM sample to the weighing tin. We measured a 4% loss in particles due to the gap between the filter paper and the filter paper holder provided by the original manufacturer; therefore, a gasket to minimize leakage is recommended. Finally, the organic fraction required only 1.5–2.5 h of drying time when it was placed in the forced ventilation chamber, and a sample recovery rate of > 98.5% was subsequently achieved. Although artifacts produced by SO2 are inevitable, the improvements we suggest can enhance the precision of PM2.5 measurements.


Keywords: Condensable particulate matter, SO2 artifact, Method 202, Stack sampling



Aerosol Air Qual. Res. 21 :200149 -. https://doi.org/10.4209/aaqr.2020.04.0149  

Don't forget to share this article 

 

Subscribe to our Newsletter 

Aerosol and Air Quality Research has published over 2,000 peer-reviewed articles. Enter your email address to receive latest updates and research articles to your inbox every second week.