| Summary: | 碩士 === 國立臺北科技大學 === 環境工程與管理研究所 === 97 === Nantou county, located at the longitudinally central part of Taiwan, is the largest county in the mid-Taiwan region and the only inland county in Taiwan. Since it is full of mountains, Nantou county is known for its agricultural developments and tourism attractions. Compared to other counties in the mid-Taiwan region, the commercial and industrial developments in Nantou county are rather limited, and thus Nantou county is less polluted than its neighboring counties. According to 2006 TEDS6.1, the emission quantity of PM is only 15%, and for other air pollutants: 2% for oxysulfide, 9% for nitrogen oxide, and 10% for non-methane hydrocarbon in the mid-Taiwan Air Quality Region. However, the poor air quality ratio (PSI>100) indicates that Nantou county has the poorest air quality in the mid-Taiwan Air Quality Region. The poor air quality ratio is 5.8% for Nantou county, 2.6% for Taichung county, 1.9% for Taichung city, and 2.1% for Zhanghua county. Therefore this study is compared to analyzes by the air quality and the meteorological data, and utilized the air quality model CAMx model(Comprehensive Air Quality Model with eXtensions) the pattern simulation, understood that the Nantou County ozone and the suspended particulate matter bad origin, and further draw up the control countermeasure.
The ozone aspect, spatial bad easy to occur in every year''s April to June and September to November . From the study of meteorological factors, the researcher identified that both high radiation and low wind speeds are the prime reasons that air pollutants in the area do not disperse easily, which leads to high Ozone density. The air direction study indicates that the Ozone density is affected by the sea, land, and air transportation activities taking place in the neighboring windward of the mid-Taiwan Air Quality Region counties, and that the mountain terrain within Nantou county also causes Ozone to be formed. Additionally, the simulated result for Ozone formation also shows that the pollution contribution ratio for the overall Taiwan region from the mid-Taiwan ARQ is 53~67%, and Nantou county has the lowest pollution contribution ratio (2~4%), among other counties, in the mid-Taiwan AQR. Zhanghua county has the highest pollution contribution ratio (21% ~44%), which is immediately followed by Taichung county (17% to 24%). If broken down by the point, line, and area pollution sources, then the line pollution source has the highest pollution contribution ratio (25%~38%), which is followed by point pollution source (19%~21%), and then area pollution source (8%~13%). Also, the northern AQR and Yunlin, Chiayi, and Tainan AQR (YCTAQR) combined contribute 9% ~ 23% pollution to the mid-Taiwan AQR.
The PM study indicates that high pollution incidences usually happen in the timeframes from January to March and from November to December. This is because the northeasterly monsoon winds grow stronger and wind speed faster during these periods, which causes the Innate Particulate Fugitive Dust Phenomenon. Also, sandy storms from China frequently visit Taiwan during this period, and thus, density for poor PM is higher. The simulation for poor PM shows the air pollution contribution for Nantou county from the mid-Taiwan AQR is 62% ~ 73%, and the contribution for the mid-Taiwan AQR from the YCTAQR, as observed from the Chushan station, is 17% ~ 19%. The pollution contribution ratios from the four counties in the mid-Taiwan AQR for the Nantou and Chushan stations are 21% ~ 33% and 29% ~ 41%, respectively. If broken down by counties, then the Taichung and Zhanghua counties have higher pollution contribution ratios(8% ~ 18%). Analyzing the contribution mix for PM density at air quality stations, the researcher also identified that both point and area pollution sources have higher pollution contribution ratios. Analyzed further, the point pollution source is mainly from the gravel industry (16%~33% at the Chushan station), and the area pollution source is mainly from road dust kicked up by vehicles driven through. (10%~12% at the Nantou station, and 7%~9% at the Chushan station).
According to the above analyses, although the pollution sources in Nantou county do not contribute significantly to Ozone formation, strict regulations on the pollution sources (diesel vehicles and wastes from the Nangang Industrial park) should still reduce the occurrences of Ozone formation incidence. To further lower Ozone density, then the local authority needs to not only enforce stricter pollution prevention measures for Nantou county, but also join forces with neighboring authorities or governments at other AQR to prevent any possible Ozone formation incidences in the future. The PM simulation result indicates that the gravel industry is the main source contributing to air pollution at the Chushan station. Thus, gravel processing factories should be the prime spots for law enforcement attention. Also, the road dust pollution also implies that the local environmental authority can implement strict controlling measures on the pollution source and work with the Fourth River Management Office to regulate in-stream gravel mining operations and related transportation practices.
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