The Evaluation of the Accuracy of the PM2.5 FRM Samplers and FEM Monitors

• Main Authors: Chen, Yu-Ting, 陳宥廷
• Other Authors: Tsai, Chuen-Jinn
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/9ezcfp

碩士 === 國立交通大學 === 環境工程系所 === 107 === The Federal Reference Method (FRM) samplers and the Federal Equivalent Method (FEM) monitors are used to measure the PM2.5 mass concentration to determine the compliance with the standards. The FRM samplers is a gravimetric method which uses the filter to collect the particles, and weight the filter before and after the sampling at least 24 hours. The sampling time of FRM is 24 hours and the flow rate of operating is 16.7 L/min. It uses the PM10 inlet and PM2.5 inlet to remove the particles that aerodynamic diameter is larger than 10 μm and 2.5 μm, respectively. The FEM class III monitors are semi-continuous and they measure the PM2.5 mass concentration more immediately than the FRM samplers. The most common FEM monitors are TEOM-FDMS and BAM-1020. Several field studies have been conducted in the NCTU in 4 months (2018/4/18-2018/8/23) and at other four cities around Taiwan, which are New Taipei city, Taipei city, Tainan city and Kaohsiung city in 18 months (2015/12/21-2017/7/21). Collocated measurements were made with the FRM samplers (PQ200) and two FEM monitors (TEOM-FDMS and BAM-1020) to measure PM2.5 mass concentration in the ambient air. The results show that the average biases of the TEOM-FDMS are 18.14 ± 13.16 % in the NCTU and 13.13 ± 14.70 % in other four sites as compared to the FRM samplers, while the average bias of the BAM-1020 is 0.85 ± 9.11 % in the NCTU and 1.89 ± 12.88 % in the four sites. It indicates that the TEOM-FDMS overestimates the PM2.5 mass concentration due to the evaporation loss in the FRM samplers. The rate of the evaporation loss is found to depend on the ambient temperature, resulting in the average bias increases with the increase in the temperature. On the other hand, the data of the BAM-1020 vary as compared to the FRM samplers, which depend on the ambient temperature and relative humidity. It is because that the BAM uses the smart heater to reduce the water vapor concentration to control the relative humidity at <35%. As the results, the BAM overestimates the PM2.5 mass concentration since the water vapor concentration difference is low due to the evaporation loss suppression but underestimates since the water vapor concentration difference higher than 800 μg/m3 due to the evaporation loss rate in the BAM higher than that in the FRM samplers.