| Summary: | 碩士 === 國立交通大學 === 環境工程系所 === 106 === Ambient PM2.5 water-soluble inorganic ions and precursor gases at the NCTU site were measured using an online monitoring system, PPWD-PILS. In order to compare the observed data and theoretical value, the hourly data was input into a thermodynamic equilibrium model, ISORROPIA-II. In addition, for discussing the chemical composition of PM2.5, TEOM-FDMS and OC-EC analyzer were used to measure PM2.5 mass concentration and PM2.5 carbon composition, respectively. Moreover, MOUDI was used to investigate the particle size distribution of water-soluble inorganic ions.
The chemical composition of PM2.5 obtained by mass reconstruction showed that the primary component of the particles was Secondary Inorganic Aerosol (SIA), and secondary is Organic Matter (OM), which accounted for 40.50 ± 11.79% and 18.49 ± 6.63 %, respectively. The reconstructed PM2.5 mass concentration accounted for 62.21 ± 15.32% of mass concentration measured by TEOM.
In comparison with ISORROPIA-II, the precursor gas NH3(g) and NH4+(p) have a good agreement, R2 is 0.83 and 0.82, respectively; HNO3(g) and NO3-(p) are scattered, and R2 is 0.12 and 0.48, respectively. The result is due to the low concentration of atmospheric HNO3(g) and NO3-(p). It is caused by not considering water-soluble inorganic ions of particles which were larger than 2.5 μm.
In the results of the water-soluble inorganic ions size distribution, the percentage of NH4+, NO3- and SO42- in the coarse particles were 10.28%, 42.76%, and 13.29%, respectively. Using the ratio of each ion in the ratio of coarse particles to fine particles, the observed PM2.5 data was adjusted to PM10 and then compared with ISORROPIA-II. The results showed that the comparison of NO3-(p) was improved, and R2 increased from 0.48 to 0.73, while HNO3(g) is still scattered, and there are also many extremely low values in ISORROPIA-II, and these values are caused by HNO3(g) reacting with NH3(g) and consuming HNO3(g). The NH3-HNO3-H2SO4 System was used to calculate the theoretical thermodynamic equilibrium and it was underestimated in NO3-.
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