In recent years, the fine suspended particle (PM2.5) concentrations of Yunlin County exceeded the legal standard. The air quality in Yunlin County even became the top three of the poorest in nationwide. To clarify the causes and sources of PM2.5 pollutants, Yunlin County Environmental Protection Agency entrusted our team to perform "Fine suspended particles (PM2.5) monitoring and investigation and assessment plan" (hereinafter referred to as this project). The aims are PM2.5 manual sampling, the major components analysis, and investigate the causes of PM2.5 variation in line with the air quality monitoring data. This project had collected PM2.5 concentration data from Douliou, Lunbei, Taihsi, Takeyama and Chiayi air quality monitoring stations. The highest daily average concentration of PM2.5 was in Chiayi station for nearly eight years, followed by the Douliou station, Takeyama station, Lunbei station and Taihsi station, and the results of hourly average concentration of each station are likewise. The high concentration event occurred at 8:00 am in Taihsi station, 10:00 am in Lunbei station, and from 2:00 pm to 8:00 pm in Douliou, Takeyama station and Chiayi station. Besides, there is a peak concentration from 8:00 to 10:00 am in each station. Moreover, the daytime concentration was higher than night time concentration, indicating that PM2.5 concentration was affected by human activities. This project conducted four manual sampling (winter, spring , summer and autumn) in Mailiao and Douliou station simultaneously. PM2.5 concentration of both stations in winter was the highest, and which in summer was the lowest. SO42- was the main ions in Mailiao station and NO3- was the main ions in Douliou. The major Carbonaceous substances of the two stations were EC, while the concentration was the highest in autumn, and the concentration in Douliou station was higher than Mailiao station. Nitrogen oxidation ratio (NOR) and Sulfur oxidation ratio (SOR) in summer were the lowest, and which in winter were the highest, indicating that the significant increase in the rate of nitrogen oxidation in winter was an important reason which caused higher nitrate concentration. In winter, the concentration of NOR and SOR in Douliou station was higher than Mailiao station. In autumn and summer, the concentration of NOR and SOR in Mailiao station was higher than Douliou station. In comparison of derivative salts (SS) and carbonaceous substances (TC), derivative salts had a more significant impact on increasing the concentration of PM2.5 for both stations. According to the research and control strategies of PM2.5, Professor Zhang Genhui indicated that the annual PM2.5 in Yunlin county affected by the transfer abroad of approximately 37%, and Professor Wu Yilin indicated that the sulfate can be completely neutralized by ammonium, but not nitrate. The results of manual sampling in this project also showed that nitrate ions were the main causes of PM2.5 in Douliou station and Mailiao station. Therefore, this project intends to strengthen controls for PM2.5 stationary source and mobile source emission to reduce the increasing of nitrate (NOx).

Air Quality Management;Air Pollution;Fine particles