本硏究分析1994-2000年間彰化市及其鄰近地區空氣品質資料，七年間彰 化市空氣品質不良曰數多（138天）於臺中市（115天）及南投（95天）》詳細分 析2000年的資料發現，造成彰化地區空氣品質不良的原因主要爲懸浮微粒，且 均發生在冬春之際。此應與彰化市位於中央山脈及八卦山西側，爲東北季風背 風面，風速微弱，且易形成逆湿層，不利於污染物之擴散有關。另一造成空氣 品質不良的污染物爲臭氧，其濃度偏髙的時間爲5月及9月。由於6-8月爲雨 季，雨水可攔截污染物，故污染物濃度不髙。而雨季前後的5月及9月，若無 梅雨或鋒面雨，則光照良好，有利於臭氧的形成。從風向來看|彰化市污染物 濃度偏高的冬季，其風向多爲北北西、西北，有利於將火力發電廠所排放之污 染物往彰化市傳送。而此季節彰化市之二氧化硫濃度明顯高於被大肚山及八卦 山阻隔的臺中市，同在山脈西側的線西測站，位於火力發電廠南方，污染濃度 多遠低於臺中市及彰化市，但二氧化硫濃度卻高彰化市及臺中市。夏季當風向 不再以西北爲主時，線西的二氧化硫濃度則低於彰化。由於火力發電廠是中部 地區二氧化硫最大的排放源，此時間及空間上的濃度變異，似乎爲火力發電廠 對彰化市空氣品質可能的影響，提供値得深入硏究的依據。

This paper is based on the air quality data for Changhua City and nearby areas from 1994-2000. During these seven years, the number of days with air quality classified as "Poor" is higher in Changhua City (138) than in Taichung City (115) and Nantou City (95). The main pollutant that caused the poor air quality was PM10 and all the days with "Poor" air quality occurred in winter and spring. Possibly because the city is located west of the Central Mountain Range and Pa-gua Mountain, the leeward side to the northeast monsoon, wind speed is low and therefore diffusion of pollutants is restricted. Ozone was the other pollutant that caused "Poor" air quality. High concentrations of ozone occurred in May and September just before and after the rainy season. The two relatively dry months are warm and have intensive sunlight, conditions suitable for ozone formation. In Changhua City the prevailing wind directions in the winter are NNW and NE that could bring pollutants emitted by the Long-gin coal-burning power plant to Changhua City. Concentrations of SO2 were always higher in Changhua City than Taichung City which is sheltered by the Ta-tu Mountain and Pa-gua Mountain. Seing-si, located south of the power plant, had concentrations of all analyzed air pollutants except SO2, lower than Taichung City and Changhua City. In the winter, when the wind directions favor transport of air pollutants from the north (where the power plant is located) to the south, SO2 concentrations were higher in Seing-si than in both Taichung City and Changhua City. However, in the sununer when the wind directions do not favor the transport of air pollutants from the north to the south, concentrations of S02 were lower in Seing-si than in Changhua City. This spatial and temporal pattern of SO2 concentrations suggests that the potential influences of the power plant on air quality in Changhua City deserve detailed study.