The indoor/outdoor relationship of acid aerosols in Taipei

Abstract

In order to estimate personal exposure to acid aerosols indirectly, we designed this study to characterize the relationship between indoor and outdoor acid aerosol concentrations in Taipei. The acid aerosols were collected using a Harvard-EPA annular denuder and analyzed by ion chromatography. Samples were collected on 4 sampling days at two sampling sites in May, 1992, and on 39 sampling days at four sampling sites from January to April, 1993. At each sampling site, both indoor and outdoor samples were collected concurrently. On each sampling day, we collected two 12-h samples in the summer and one 24-h sample in the winter. We found that acid aerosols in Taipei are rich in SO 2, NH 3, ammonium nitrate and sulfate. We also found that indoor/outdoor ratios were > 1 for HNO 2, NH 3, NO 3 −, NH 4 + and H +, but < 1 for SO 2, SO 4 2− and HNO 3. The outdoor SO 4 2− levels were correlated with outdoor SO 2 levels, while the indoor SO 4 2− levels were correlated with indoor NH 4 + levels. The indoor SO 4 2− may originate from outdoor SO 2 emissions and then penetrate indoors in the form of (NH 4) 2SO 4 or (NH 4)HSO 4 in Taipei. We conclude that mobile sources can be one important source of acid aerosols in Taipei. The concentrations of acid aerosols, indoors and outdoors, are possibly controlled by factors such as hot and humid weather and crowded living space in Taipei.