| Summary: | 碩士 === 國立交通大學 === 環境工程系所 === 101 === In this study, the Multi-Filter PM10-PM2.5 Sampler (MFPPS), two reference FRM samplers including Dichotomous and EPA WINS PM2.5 sampler, and a real-time monitor FDMS (Filter Dynamic Measurement System, FDMS, Model 1405-DF, Thermo) were collocated in National Chiao Tung University to conduct the 24-h comparison tests. Three Teflon filters and a pore metal denuder (PMD) were assembled in MFPPS. In order to evaluate the effect of sampling artifacts on the mass concentrations measured by the PM2.5 manual samplers during sampling or conditioning process, the samples in MFPPS were analyzed by different subsequent analysis methods, and the mass and ions concentrations of PM¬2.5 were compared with those measured by FRM and FDMS samplers.
The results showed that the PM2.5 mass concentrations measured by FRM sampler agreed well with those measured by base flow in FDMS(PM2.5, Fb). However, the PM2.5 mass concentrations were lower than those measured by base flow-reference flow in FDMS (PM2.5, F(b-r)). This indicated that the manual samplers underestimated the PM2.5 mass concentrations due to the evaporation of semi-volatile species of PM2.5 samples in the duration. In this study, the PMD was fixed in the MFPPS to modify the sampling artifacts. The mass concentrations of PM2.5,Md and FDMS(b-r) were very close. This implied that the evaporation of inorganic species in the PM2.5 samples during sampling were significant. During 20 times of sample tests, the ratio of NH4NO3 and NH4Cl volatilized mass concentrations to total PM2.5 mass concentrations ranged from 6 to 30% with an average of 16%. It was observed that the volatilization amount tended to decrease with the increase of PM2.5 mass concentrations. Compared with total NH4+, NO3- and Cl- in particulate, evaporative NH4+, NO3- and Cl- loss ranged from 18-80 % (ave. 48 %), 22-94 % (ave. 60 %), and 49-91 % (ave. 78 %), respectively.
In this study, the artifacts of conditioning process after sampling were also evaluated. It was found that the ratio of decrease amount to total PM2.5 mass concentrations with 48-h conditioning process were less than 3% (ave. 1%). After 120 hours conditioning process, the ratio ranged from 1 to 7% (ave. 5%). This implied that the decrease amount due to conditioning process was insignificant compared with the total particle mass.
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