098

3,800 千元

2009/03/24

2010/03/24

張士昱

臺中市政府環境保護局

謝淑如

國立中山醫學大學

大氣空氣

衍生性、氣膠、調查

secondary、aerosol、survey

林延睿

04-24730022#11796

cherng5568@yahoo.com.tw

本計畫收集2000-2007年台中縣7個監測站(大甲、后里、豐原、沙鹿、太平、大里、烏日) 之空品資料，進行逐年PM10濃度趨勢分析，由季節比較可發現夏季各測站PM10之濃度為最低。由區域別來比較，發現屯區之平均PM10濃度為最高，若以測站別來比較，則以大甲測站為最高。另進行台中縣3座環保署監測站2005-2007年PM2.5濃度趨勢分析，由季節比較可發現夏季之各測站PM2.5濃度為最低，由區域別來比較，發現屯區之平均濃度為最高，若以測站別來比較，則以大里測站為最高。計算PM10事件日(PM10≥125µg/m3)可發現屯區發生PM10事件日之天數為最多，其中較特別的為山線之后里測站於2007年出現較高之事件日數，係由中科后里園區開挖所影響。 在懸浮微粒之逐日化學組成方面，本計畫共採樣四次，包括春、夏、秋、冬四季，衍生性鹽類以秋季之濃度為最高，冬季因採樣期間遇短暫陣雨，其濃度偏低，衍生性有機碳則以夏季有較高濃度。在測站之比較上，衍生性鹽類及衍生性有機碳大部份樣品在大里測站及大甲測站有較高測值，但七個測站間，不論細粒徑或粗粒徑衍生性鹽類其濃度均未達統計上之顯著差異，但細粒徑或粗粒徑衍生性有機碳，其濃度在七個測站間均達統計上之顯著差異。在粗、細微粒之比較上，衍生性鹽類及衍生性有機碳均是細粒徑之濃度明顯高於粗粒徑之濃度。在日間與夜間之比較上，衍生性鹽類其日間與夜間之濃度並無統計上之顯著差異，而衍生性有機碳其日間與夜間之濃度呈統計上之顯著差異，且日間濃度顯著高於夜間之濃度。由季節及日夜之數據，可推論衍生性有機碳相較於衍生性鹽類更易受光化作用之影響。綜合四季之測值，發現細粒徑衍生性氣膠(衍生性有機碳及衍生性鹽類)佔細粒徑懸浮微粒約32%~42%，而粗粒徑衍生性氣膠佔粗粒徑懸浮微粒約18%~24%。 空氣污染具有時間與空間的變異性，為了明確辨別污染物為本地生成或是境外輸入，本計畫使用現址式氣膠組成量測技術於沙鹿與烏日測站探討空氣污染的特性。在受到海陸對流風的影響下，沙鹿測站在夜間往往可觀測到高濃度PM10的污染發生；然而烏日測站的逐時量測結果卻可發現每日有兩次PM10濃度峰值的發生，分別發生在早上與傍晚。分析PM10氣膠的化學組成可發現NO3-與NH4+的濃度時間序列變化與PM10氣膠逐時濃度的變化一致，而每日臭氧最高濃度與當時測得的NO3-濃度間具有良好的線性相關性，由此可顯示經由光化反應所生成的二次NO3-氣膠對於空氣品質的影響具有重要地位。依據海陸風對流傳輸與當地污染排放特徵，沙鹿地區所排放的空氣污染物在日間經由海風的傳輸可到達較為內陸地區的烏日，並參與當地具都會特性空氣污染物的光化反應；在夜間，內陸地區以生成的二次污染物可再被傳輸至沙鹿地區。如此交互影響的反應機制增加控制二次污染的複雜性。 在資料分析與模式模擬方面，本研究利用Rawins 技術，改善氣象模式模擬近地層風速高估之缺點並且也改善空氣品質模式之模擬能力。由四季採樣期間資料分析可知，台中地區的平均空氣污染物以秋季為最高，其次為春季，夏季平均濃度為最低。模擬結果與觀測資料比較也顯示，此模式可掌握中部空氣品質的變化趨勢，特別是臭氧與PM2.5。

衍生性、氣膠、調查

98年台中縣衍生性氣膠調查計畫期末報告(定稿).pdf

31MB

2010/8/1 上午 12:00:00

The data of air pollutants were collected from seven air-quality monitoring stations (Dajia, Houli, Shalu, Fengyuan, Taiping, Dali, and Wurih) distributed throughout Taichung County from 2000 to 2007. The year and seasonal variations of PM10 concentrations were analyzed. The lowest concentration was observed in summer for every air quality station. Among the three districts, the highest average concentration of PM10 occurred in the Tun district; whereas, among the seven stations, the highest PM10 concentration was found at the Dajia station. Similar phenomena were observed in PM2.5 concentrations, except that the highest PM2.5 concentration was found in the Dali station. The occurrence frequencies of PM10 episode days (PM10≥125µg/m3) were very high in the Tun district. It was noticed that the number of PM10 episode days in the Houli station was increased in 2007 due to the development of the Houli Science Park. Analysis results of the daily chemical compositions of suspended particles among the four seasons indicated that the concentrations of the secondary salts showed the highest value in autumn. The secondary-salt concentrations were slightly lower in winter due to few showers, and the concentrations of secondary organic carbons were higher in summer. Among the seven stations, most of the samples from the Dajia and Dali stations showed higher concentrations of secondary salts and organic carbons. Both the concentrations of coarse and fine secondary salts among the seven stations showed that the differences were not statistically significant. However, the concentrations of both fine and coarse secondary organic carbons showed statistically significant differences among the seven stations. In addition, the size distribution of secondary salts and organic carbons were mainly distributed in a fine mode. The concentrations of secondary organic carbons were significantly higher in the daytime than in the nighttime. However, these phenomena were not observed for the daytime and nighttime secondary salts. According to the above results, this study proposed that the photochemical influences are more notable for the secondary organic carbons than the secondary salts. Overall, the mass fractions of the fine secondary aerosols (including secondary salts and organic carbons) of the fine mode aerosols were 32~42%, which is higher than the mass fractions of coarse secondary aerosol in the coarse mode aerosols (18~24%). Air pollutants displayed rapid changes of spatial and temporal variations. In order to clearly discriminate local and external contributions of atmospheric particulate matter, this work applied an in-situ particulate composition technique to characterize ambient pollution in the Shalu and Wurih stations. Under the influence of sea-land breezes, the concentration peaks of PM10 were mainly observed at night at the Shalu station. However, the curve of PM¬10 of hourly concentrations at the Wurih station showed a bi-modal distribution, with the first peak in the morning and the secondary peak in the evening. Analysis on chemical compositions of PM10 found that hourly time series of NO3- and NH4+ concentrations were consisted with that of the PM10 concentrations. Good linear correlations were found at the same time between daily maximum O3 concentrations and NO3- concentrations, which clearly shows that secondary aerosol formation of NO3- by photochemical reaction played an important role in air quality. According to the influences of sea-land breeze transport and the characteristics of local pollutant emissions, the pollutants from Shalu could be transported to the inner land of Wurih, and then reacted with urban pollutants during the day. During the night, the formatted secondary pollutants of photochemical reaction in Wurih could be transported to Shalu. Interactions between the two mechanisms increased the complexity in order to control secondary pollutants. For the air pollutants data analysis and modeling study, the use of the Rawins scheme in the meteorological model showed significant improvement near the surface wind speed estimation, and hence, could improve our air quality modeling study. Data showed that the 3rd monitoring period (fall season) has the highest average air pollutants concentrations, while the 2nd monitoring period (summer season) has the lowest. Simulation results confirmed that the proposed model could reasonably simulate the variation trends in central Taiwan, especially for O3 and PM2.5.

secondary、aerosol、survey