都會區酸性氣膠特性研究

Abstract

本研究主要探討台北市地區酸性氣膠的特性，採樣地點在台北市環保署中山監測站，使用固氣分離器(ADS)吸收大氣氣體及微粒具有2.5μm及lOμm兩種不同截取直徑的旋風分離器以分離粗微粒(ADS10)和細微粒(ADS2.5)。酸性氣膠主要化學成分為銨根離子、硫酸根離子、硝酸根離子及氯離子，其酸性以氫離子的濃度作為指標。大氣中高濃度的氨氣會中和氣膠 中的酸性，造成台北市大氣中氣膠酸性的降低。氫離子和硫酸根離子的比值可作為酸性氣膠的組成成分的良好指標，台北市的酸性氣膠主要以硫酸銨及(NH4)3H(SO4)2的形式存在。氣體和固體微粒除了氯離子之外，其濃度在春天皆較在其他季節的濃度為高。ADS10和ADS2.5所得的化學物質濃度，和環保署中山監測站的物種濃度，具有高度的相關性。

The characteristics of acidic aerosols in Taipei, Taiwan were investigated in this study. The application of annular denuder/filter pack system (ADS) made it possible to collect gases in the denuder tubes and particles at the after filters simultaneously. ADS2.5 and ADS10, were used in the study. The cutoff aerodynamic diameters for the inlet cyclones of ADS2.5 and ADS10 are 2.5 μm and 10 μm respectively. The main particulate components of acidic aerosols were found, to be NH4+,SO42-,NO3-, and Cl-. The elevated concentrations of NH3 were found to neutralize particles, resulting in reduction of acidity of aerosols in Taipei. The acidity of aerosols is represented by hydrogen ions (H+) concentration in the aerosols. The ratio of H+/SO42- gives a good index of chemical compositions in sulfate acidic aerosols. In Taipei, sulfate aerosols were normally found to exist as (NH4)2SO4 and letovicite. The particulate and gaseous concentrations were found to be higher in spring than in other seasons except for those of Cl- ions. The correlation of species concentrations of ADS2.5 and ADS10 with criteria pollutant concentrations obtained from the Taiwan EPA (Environmental Protection Agency) monitoring station were found to be significant in general.