Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6343554 | Atmospheric Research | 2014 | 11 Pages |
Abstract
Daily PM2.5 and hourly water-soluble inorganic ions in PM2.5 and gaseous precursors were measured during June-November 2009 at an urban site in Beijing. The average mass concentration of the total water-soluble ions was 44 μg mâ 3, accounting for 38% of PM2.5. Sulfate (SO42 â), nitrate (NO3â) and ammonium (NH4+) were dominant ions. The summer-fall difference in seasonal average mass concentrations was smaller than 30% for SO42 â, but was up to a factor of 2.0 for NO3â and NH4+. A pronounced diurnal cycle was found for most ions and gaseous precursors and could be explained by their respective sources, formation mechanisms and meteorological conditions. The average oxidation/conversion ratio for SO42 â (SOR), NO3â (NOR) and NH4+ (NHR) were estimated to be 63%, 15% and 15%, respectively. The low NHR value suggests that NH3 was mainly from local sources and that excessive NH3 existed and thus was not a limiting factor in the formation of NH4+. As a result, the diurnal pattern of NH4+ was similar to that of SO42 â to some extent, but differed significantly from that of NH3. Based on the estimated H+ concentration and acidity purity (f), 75% of data samples were strongly acidic and a few percent might be alkaline. Seasonal variations in aerosol acidity and chemical forms of major ions were also briefly discussed.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Atmospheric Science
Authors
Guoyuan Hu, Yangmei Zhang, Junying Sun, Leiming Zhang, Xiaojing Shen, Weili Lin, Yun Yang,