- 期刊
- OpenAccess
Pollution Properties of Water-Soluble Secondary Inorganic Ions in Atmospheric PM_(2.5) in the Pearl River Delta Region
並列摘要
Based on the online observation of PM_(2.5) mass concentration, its water-soluble inorganic ions, and their gaseous precursors during August of 2013 to March of 2014 at the atmospheric supersite in the Pearl River Delta (PRD) region, the inter-action of the secondary compositions and their precursors was discussed, and the pollution properties of the secondary inorganic ions were revealed. During the whole measurement period, the average concentrations of SO_4^(2-), NO_3^- and NH_4^+ were 16.6 μg m^(-3), 9.0 μg m^(-3) and 10.2 μg m^(-3), respectively, with total contribution to PM_(2.5) of 55.8%, indicating the significant role of secondary transformation in PM_(2.5) pollution. The seasonal average total contributions of SO_4^(2-), NO_3^- and NH_4^+ to PM_(2.5) varied from 46.0% to 64.3%, lowest in summer and highest in winter. The contributions of SO_4^(2-) and NH_4^+ to PM_(2.5) were relatively stable; while those of NO_3^- in different seasons were distinct, even dominating PM_(2.5) in some pollution cases in winter. NH3 was abundant with an annual average concentration of 15.2 μg m^(-3), facilitating the neutralization of H_2SO_4 and HNO_3 with the average [NH_4^+]/(2[SO_4^(2-)] + [NO_3^-]) equivalent charge ratio of 1.1. The maximum daily peak concentration of HNO_3 was as high as 18.6 μg m^(-3), providing an evidence for the strong oxidizing property of the atmosphere in the PRD region. The theoretical equilibrium constant (K_e) of NH_4NO_3 is always lower than the observed concentration product (K_m=[NH_3] × [HNO_3]) in spring and winter with higher HNO_3 concentrations; while in over 60% of the time during summer and autumn, mainly during daytime, K_e was higher. In general, the strong oxidizing property and NH3 played important roles in the fine particle pollution in the PRD region.
延伸閱讀
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