Size distribution and water soluble ions of ambient particulate matter on episode and non-episode days in southern Taiwan

Abstract

Distribution of inorganic ions at an urban/industrial/agricultural complex was investigated in southern Taiwan during particulate matter (PM) episode and non-episode periods, and the Micro Orifice Uniform Deposit Impactor (MOUDI) and nano-MOUDI were employed to take PM samples. In PM episode periods, the PM significantly increased in mass concentration and in the size ranges of 0.1-1.0 and 1.8-18 μm at the site. Sulfate, nitrate and ammonium were the dominant ionic species and contributed a large fraction of PM mass in different sizes. The nitrate concentration increase on episode days could be attributed to the increase of precursor gas-NO 2 concentration during these periods. In addition, SO 2 was significantly correlated to SO 42- in the nuclei mode (PM 0.1), which indicated that the gas had transferred into particulate matter. The molar equivalent ratio of {[NO 3-] + [SO 42-]}/[NH 4+] was about 0.99 and revealed a high correlation that could indicate the presence of ammonium nitrate and ammonium sulfate in PM1. © Taiwan Association for Aerosol Research.