A Study of Characteristics and Sources of Aerosol in Typical Indoor and Outdoor Environments in Taipei

• Main Authors: Tzu-Ting-Yang, 楊慈定
• Other Authors: Chiu-Sen-Wang
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/ttuv3t

碩士 === 國立臺灣大學 === 環境衛生研究所 === 88 === ABSTRACT The primary objective of this study was to investigate the mass concentrations ambient and indoor aerosols in typical Taipei buildings with natural ventilation and no indoor particle sources. The air exchange rate and the particle deposition loss rate were determined for each indoor environment studied. The concentration data and the indoor-to-outdoor concentration ratio (I/O ratio) of PM2.5 were then used to caculate the penetration factor using the mass balance principle. Particulate n-alkanes with carbon numbers from 23 to 26 were used as tracers for vehicular emissons for evaluating the contribution of vehicular emissions to the fine fraction of ambient aerosols and fine particles in indoor environments. The sites selected for study included a classroom on the third floor of a school building, an apartment on the third floor,and an office on the first floor. Two impactors (Micro-environment Monitor, MSP Corp., Minneapolis, MN, USA), with a cut-off aerodynamic diameter of 2.5 mm and a sampling flowrate of 10 lmin-1, collected fine particles on quartz fiber filters both indoors and outdoors of selected buildings. Sampling was conducted from 8:00 a.m. to 3:30 p.m. at the classroom, from 8:00 a.m. to 5:00 p.m. at the apartment and office during November 1999 to April 2000. After weighing, the samples were extracted with CH2Cl2 and then analyzed for n-alkanes by a gas chromatography/flame ionization detector system (HP 5890, Hewlett-Packard, Avondale, PA, USA). In this study, we used the CPI of C23 to C26 n-alkanes to estimate the contribution of vehicular emissions, based on the data that the ratio is about 1.08 for vehicular emissions and about 2.57 for tree leaves wax. We also collected fine particles in an underpass which is located in the center of Taipei city. The samples were used to determine the concentrations of n-alkanes with carbon numbers 23 to 26 in vehicular emissions. The I/O ratio of PM2.5 for the apartment had an average value of 0.91 with a standard deviation of 0.09 for a total of 28 daytime samples, and an average value of 0.79 with a standard deviation of 0.05 for a total of 22 nighttime samples. The I/O ratio of PM2.5 for the classroom had an average value of 0.91 with a standard deviation of 0.13 for a total of 14 daytime samples, and an average value of 0.89 with a standard deviation of 0.09 for a total of 14 daytime samples. The daytime I/O ratios of PM2.5 did not show significent differances among the apartment, the classroom, and the office, when the doors and windows were opened. The penetration factor of fine particles for the apartment had an average value of 0.92 with a standard deviation of 0.09 for a total of 28 daytime samples. The penetration factor of fine particles for the apartment had an average value of 0.83 with a standard deviation of 0.06 for a total of 22 nighttime samples. The penetration factor of fine particles for the office had an average value of 0.90 with a standard deviation of 0.09 for a total of 14 daytime samples. The percentage of fine particles that penetrated small openings of the buildings was 0.83 for the apartment, the classroom, and the office, indicating that small openings of the buildings were not efffective to remove fine paticles. The regression equation for the mass fractions of C23 to C26 n-alkanes in indoor and outdoor fine particles was y=1.09x+0.02, R2=0.53, m=1.09, where y represented the indoor mass fration This implies that the I/O ratio of the mass fractions of C23 to C26 n-alkanes in fine particles which was 1.09. The results indicate that particles from vehicular emissions contributed a greater fraction to indoor fine particles than to outdoor fine particles. This is prabably because particles in vehicular emissions, which are mainly in the size range of 0.1 to 1 mm, have relatively low deposition rates. The results of this study show that vehicular emissions contributed about 50% of indoor aerosols in typical classrooms and residential buildings in Taipei. Because particles in vehicular emissions are mainly in the submicrometer range, they tend to have longer residence times in indoor air and , as a consequence, may have a greater health risk. Keywords: urban aerosols, indoor environments, PM2.5 , vehicular emissions