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

Duanyang Liu; Yan Su; Huaqing Peng; Wenlian Yan; Yi Li; Xuejun Liu; Bin Zhu; Honglei Wang; Xiliang Zhang

doi:10.4209/aaqr.2018.04.0123

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

Duanyang Liu ¹^,2, Yan Su³, Huaqing Peng³, Wenlian Yan¹^,2, Yi Li⁴, Xuejun Liu⁵, Bin Zhu⁶, Honglei Wang⁶, Xiliang Zhang⁷

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

Received: April 25, 2018
Revised: August 10, 2018
Accepted: August 12, 2018
Download Citation: ||https://doi.org/10.4209/aaqr.2018.04.0123

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Cite this article:
Liu, D., Su, Y., Peng, H., Yan, W., Li, Y., Liu, X., Zhu, B., Wang, H. and Zhang, X. (2018). Size Distributions of Water-soluble Inorganic Ions in Atmospheric Aerosols during the Meiyu Period on the North Shore of Taihu Lake, China. Aerosol Air Qual. Res. 18: 2997-3008. https://doi.org/10.4209/aaqr.2018.04.0123

HIGHLIGHTS

The fine particles have increased to coarse particles before the Meiyu period.
The ions spectral distributions are in bimodal or trimodal distributions.
SNA (SO₄^2–, NO₃^–, and NH₄⁺) are the main components of the PM_1.1 and PM_1.1-2.1.
The secondary aerosol formation of SO₄^2– 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 PM_1.1 (aerodynamic diameter ≤ 1.1 µm) grew in particle size, becoming PM_1.1-2.1 (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 SO₄^2–, NO₃^–, and NH₄⁺ were all bimodal or trimodal before Meiyu, and SNA (SO₄^2–, NO₃^–, and NH₄⁺) was the main component of the PM_1.1 and PM_1.1-2.1. Vehicle emissions were more important and the secondary formation of SO₄^2– 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 NO_x infrequently occurred in Wuxi compared to that of SO₄^2– 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 [SO₄^2– + NO₃^– + NO₂^– + Cl^–].