Characteristics of PM2.5, acidic and basic gases and conversion rate of sulfur dioxide to sulfate in central Taiwan

• Main Authors: Chuen-Liang Horng, 洪春量
• Other Authors: 鄭曼婷
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/27990768136586918539

博士 === 國立中興大學 === 環境工程學系所 === 96 === This study mainly investigated the characteristics of PM2.5 and gaseous species in the inland area of central Taiwan. Moreover, characterization of PM2.5, acidic and basic gases near coastal in central Taiwan were also studied. Subsequently the conversion rate of sulfur dioxide to sulfate in central Taiwan was also investigated by experimental results. Measurements of PM2.5 and acidic gases were conducted at an inland site of Taichung basin during the sampling timings in the month of April and September of 2005. Results showed that the average PM2.5 concentration were 41.3 μg m-3 during April and 65.3 μg m-3 during September. The major particle-phase ionic species was sulfate during both sampling months. Ozone concentration was higher during September. Sulfate and nitrate concentrations were well correlated with daily maximum ozone concentration. The time weight mean concentration data showed that the increased concentration of gas-phase sulfur dioxide and sulfate were transported from the Taichung city, which is located close to the sampling site. Based on our above obtained results, during September period showed more anthropogenic impact on the aerosol and gaseous distribution favored by meteorological factors, higher ambient temperature and wind direction. Similarly, measurements were conducted at inland Nantou and coastal Erlin of central Taiwan region during May and October of 2006. The PM2.5 concentrations were 41.1 and 32.9 μg m-3 at Nantou and Erlin sites respectively. The average concentration of three main ionic species SO42－, NO3－ and NH4＋accounted to 44 % for PM2.5 indicating that the formation was mainly via secondary process. These percentage of ionic SO42－, NO3－ and NH4＋ were similarly with other published in central Taiwan. The PM2.5, HNO3, NO3－, NO, NO2 and CO were highest at Nantou site compared to Erlin site. Based on the results of this study we conclude that, higher traffic emissions coupled with poor ventilation due to topography of the area caused higher HNO3, NO3－, NO, NO2 and CO concentrations in Nantou. Furthermore, the evaluation of nitrate aerosol showed the correlation coefficients between observed and calculated concentrations were 0.74 and 0.66 at Nantou and Erlin, respectively. Finally, to investigate the sulfur conversion rate the measurements were taken at two different sites in central Taiwan. The distance between two sites is about 15 km. Results showed that the average ratio of PM2.5 and SO42－ was higher during daytime probably due to the anthropogenic activities. Wind filed map also clearly displayed that Wufong was located upwind and Nantou was located downwind during daytime. Sulfur conversion ratio in the downwind site was higher than upwind site. Experimental data showed that sulfur conversion rate between these sites was 5 - 9 % hr－1. The value of sulfur conversion rate was consistent with other published. The increased PM2.5 and SO2 concentrations recorded in downwind site was from the direction of Taichung city during daytime.