Due to the unique landform, the population and industrial activities are concentrated in the western parts of Taiwan, resulting high density of mobile and stationary air pollution sources. In conjunction with poor meteorology condition and transboundary air pollution from China, air quality can be very poor in some regions. The percentage non－attainment days in Central Air Quality Zone has decreased from 5.89％ in 2004 to 0.89％ in 2013. The percentage non－attainment days in Taichung Area has decreased from 5.89％ in 2004 to 0.89％ in 2013； the percentage non－attainment days in Yun－Chia－Nan Air Quality Zone has also decreased from 5.93％ in 2004 to 2.96％ in 2013. Efforts from the environmental authorities have led to significant improvements in air quality. Both Central and Yun－Chia－Nan Air Quality Zones can comply with the ozone air quality standard. For PM10, all control regions in the Central Air Quality Zone were classified as Class 2； control regions in the Yun－Chia－Nan Air Quality Zone were classified as Class 3. For PM2.5, all control regions were not able to comply with the annual average of 15g／m3. To further improve the air quality, EPA launched this emission reduction project. This project has three main tasks：
1. Emission reduction in air quality zones:
In Central Air Quality Zone, PM10 was non－attainment for 7 times, averaging 0.8 times per station. It is mainly due to haze from China（29％）, poor dispersion due to high atmospheric pressure（57％）, and burning of agricultural wastes（14％）. In Yun－Chia－Nan Air Quality Zone, PM10 was non－attainment for 86 times, averaging 9.6 times per station. Other than the above mentioned reasons, dust storms from China and river beds in Taiwan are also possible causes for poor PM10 quality.In Central Air Quality Zone, PM2.5 was non－attainment for 102 times, averaging 11.3 times per station. In Yun－Chia－Nan Air Quality Zone, PM2.5 was non－attainment for 129 times, averaging 14.3 times per station. The reason for non－attainment days was still unknown for about 50％ of the cases. We have observed that the concentration of the PM2.5 was generally higher in the inland regions than the coastal regions, especially in Douliu and Zhushan monitoring stations. The pollutants may be trapped in the valley in Taichung and Nantao Area.According to the results from photochemical monitoring stations, ethylene, propylene, toluene, and m－, p－xylenes are the main contributor for ozone formation potential （OFP）. The OFP has decreased by 30％ since 2007, and the number of ozone non－attainment days has decreased by 94％, showing that emission of VOCs was significantly reduced.Benzene contributed about 50％ to the Hazard Index（HI）. Mobile emission sources are the main sources for benzene. In 2000, the benzene in the gasoline was decreased from 5％ to 1％. The ambient ozone concentration has decreased to 0.88ppb in 2013, which lower than the EU and USEPA standards.Three exhibitions were held to address reduction strategy for the stationary, mobile and fugitive emission sources.
2. Emission Control in Taichung Port and Industrial Parks:
Emissions in Taichung Ports are mainly from stationary sources. However, the PM2.5 concentration is mainly effected by the mobile and fugitive sources. PM10 has decreased from 30.7g／m3 in 2007 to 14.7g／m3 in 2013, mainly due to the implementation of fugitive dust control regulations. Burning Towers in Renda Industrial Park was identified as a major emission source for ethylene. In Xiaogang, storage tanks, chemical loading, and mobile sources are major emission sources of benzene. They are the targets for emission reductions.
3. Emission Control in the Sixth Naphtha Cracking Plant:
The VOCs emission report from the Sixth Naphtha Cracking Plant was reduced by 30％ since 2007. The ethylene and benzene concentration detected in the Taixi photochemical monitoring station was reduced by 75％ and 53％ respectively, showing that the VOCs emission was really reduced over the years. Reduction came from the reduction of flaring, leak detection and repair, and retrofitting of storage tanks.
4. The Revision of Stationary Sources Emission Standards:
In 2014, revisions to the air pollutant emission standards for glass furnaces and electricity facilities were passed. The emission standard for glass furnaces were divided into two categories, air－fueled and oxygen－fueled. The NOx emission standard for air－fueled furnaces is 180 ppmv； the NOx emission standard for oxygen－fueled furnaces is 3kgNOx／tone glass. The air pollutant emission standards for electricity facilities lowered the standards for the emission of PM2.5 and its precursors. Mercury emission standard was also implemented. It is estimated that the annual average of PM2.5 would reduce 0.4~2.0g／m3.
