Size Distribution and Water Soluble Ions of Ambient Particulate Matter on Episode and Non-episode Days in Southern Taiwan

摘要

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-NO2 concentration during these periods. In addition, SO2 was significantly correlated to SO42– in the nuclei mode (PM0.1), which indicated that the gas had transferred into particulate matter. The molar equivalent ratio of {[NO3–] + [SO42–]}/[NH4+] was about 0.99 and revealed a high correlation that could indicate the presence of ammonium nitrate and ammonium sulfate in PM1.