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Size Distributions of Water-soluble Inorganic Ions in Atmospheric Aerosols during the Meiyu Period on the North Shore of Taihu Lake, China

Category: Aerosol and Atmospheric Chemistry

Article In Press
DOI: 10.4209/aaqr.2018.04.0123
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Duanyang Liu 1,2, Yan Su3, Huaqing Peng3, Wenlian Yan1,2, Yi Li4, Xuejun Liu5, Bin Zhu6, Honglei Wang6, Xiliang Zhang7

  • 1 Key Laboratory of Transportation Meteorology, China Meteorological Administration, Nanjing 210008, China
  • 2 Meteorological Observatory of Jiangsu Province, Nanjing 210008, China
  • 3 Meteorological observatory of Wuxi in Jiangsu Province, Wuxi 214101, China
  • 4 Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523, USA
  • 5 College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China
  • 6 Key Laboratory for Atmospheric Physics and Environment CMA, Nanjing University of Information Science and Technology, Nanjing 210044, China
  • 7 Huzhou Meteorological observatory of Zhejiang Province, Huzhou 313000, China

Highlights

The fine particles have increased to coarse particles before the Meiyu period.
The ions spectral distributions are in bimodal or trimodal distributions.
SNA (SO42–, NO3, and NH4+) are the main components of the PM1.1 and PM1.1-2.1.
The secondary aerosol formation of SO42– and NO3 is easier during the Meiyu period.
[NH4+ + Ca2+] is fairly sufficient to neutralize anion.


Abstract

In order to research the impact on air pollution from Meiyu (a special period of seasonal heavy rainfall between late May and June in the middle-lower Yangtze area in China (Qian et al., 2009)), the pollutant gas concentrations, size distributions, and water-soluble inorganic ions of aerosols were measured on the north shore of Taihu Lake from June 10 to June 26, 2014. Results show that the PM1.1 (aerodynamic diameter ≤ 1.1 µm) grew in particle size, becoming PM1.1-2.1 (1.1 µm ≤ aerodynamic diameter ≤ 2.1 µm) and then CPM (coarse particle matter; aerodynamic diameter > 2.1 µg) due to coagulation growth and chemical reactions, prior to Meiyu. The ions, anions, and cations all exhibited bimodal distributions before Meiyu, with peak positions of 0.43–1.1 and 9–10 µm, and trimodal distributions during Meiyu, with unfixed peak positions. The spectral size distributions of the SO42–, NO3, and NH4+ were all bimodal or trimodal before Meiyu, and SNA (SO42–, NO3, and NH4+) was the main component of the PM1.1 and PM1.1-2.1. Vehicle emissions were more important and the secondary formation of SO42– from SO2 occurred more readily during Meiyu than before Meiyu. The nitrogen oxidation ratio (NOR) was lower than the sulfur oxidation ratio (SOR), and the secondary formation of NO3 from NOx infrequently occurred in Wuxi compared to that of SO42– from SO2. The samples collected during the pre-Meiyu season and Meiyu all fell below the line 1:1 (CE:AE) (cation equivalence:anion equivalence), suggesting that the volatilization of ammonium and nitrate as well as unmeasured hydrogen ions may have caused the loss of cations, which resulted in insufficient cations for neutralizing the anions and subsequently, acidic properties for the aerosol. [NH4+ + Ca2+] are evidently sufficient for neutralizing [SO42– + NO3 + NO2 + Cl].

Keywords

Fine particles Size distribution Water-soluble inorganic ions Meiyu Taihu Lake


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