Evaluation of Bias in the Measurement of Condensable Particulate Matter with Method 202
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 re...
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Springer
2020-08-01
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| Series: | Aerosol and Air Quality Research |
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| Online Access: | https://doi.org/10.4209/aaqr.2020.04.0149 |
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| author | Yu-Mei Huang Sheng-Hsiu Huang Chih-Wei Lin Hsi-Hsien Yang Chih-Chieh Chen |
| author_facet | Yu-Mei Huang Sheng-Hsiu Huang Chih-Wei Lin Hsi-Hsien Yang Chih-Chieh Chen |
| author_sort | Yu-Mei Huang |
| collection | DOAJ |
| description | 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. |
| format | Article |
| id | doaj-art-96ea79b1353441d68a79469ff2c0e56b |
| institution | Kabale University |
| issn | 1680-8584 2071-1409 |
| language | English |
| publishDate | 2020-08-01 |
| publisher | Springer |
| record_format | Article |
| series | Aerosol and Air Quality Research |
| spelling | doaj-art-96ea79b1353441d68a79469ff2c0e56b2025-02-09T12:20:47ZengSpringerAerosol and Air Quality Research1680-85842071-14092020-08-0121111210.4209/aaqr.2020.04.0149Evaluation of Bias in the Measurement of Condensable Particulate Matter with Method 202Yu-Mei Huang0Sheng-Hsiu Huang1Chih-Wei Lin2Hsi-Hsien Yang3Chih-Chieh Chen4Institute of Environmental and Occupational Health Science, College of Public Health, National Taiwan UniversityInstitute of Environmental and Occupational Health Science, College of Public Health, National Taiwan UniversityInstitute of Environmental and Occupational Health Science, College of Public Health, National Taiwan UniversityDepartment of Environmental Engineering and Management, Chaoyang University of TechnologyInstitute of Environmental and Occupational Health Science, College of Public Health, National Taiwan UniversityAbstract 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.https://doi.org/10.4209/aaqr.2020.04.0149Condensable particulate matterSO2 artifactMethod 202Stack sampling |
| spellingShingle | Yu-Mei Huang Sheng-Hsiu Huang Chih-Wei Lin Hsi-Hsien Yang Chih-Chieh Chen Evaluation of Bias in the Measurement of Condensable Particulate Matter with Method 202 Aerosol and Air Quality Research Condensable particulate matter SO2 artifact Method 202 Stack sampling |
| title | Evaluation of Bias in the Measurement of Condensable Particulate Matter with Method 202 |
| title_full | Evaluation of Bias in the Measurement of Condensable Particulate Matter with Method 202 |
| title_fullStr | Evaluation of Bias in the Measurement of Condensable Particulate Matter with Method 202 |
| title_full_unstemmed | Evaluation of Bias in the Measurement of Condensable Particulate Matter with Method 202 |
| title_short | Evaluation of Bias in the Measurement of Condensable Particulate Matter with Method 202 |
| title_sort | evaluation of bias in the measurement of condensable particulate matter with method 202 |
| topic | Condensable particulate matter SO2 artifact Method 202 Stack sampling |
| url | https://doi.org/10.4209/aaqr.2020.04.0149 |
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