Characteristics of Water-Soluble Inorganic Components and Acidity of PM2.5 in a Coastal City of China

Xin Wu; Junjun Deng; Jinsheng Chen; Youwei Hong; Lingling Xu; Liqian Yin; Wenjiao Du; Zhenyu Hong; Nanzhen Dai; Chung-Shin Yuan

doi:10.4209/aaqr.2016.11.0513

Characteristics of Water-Soluble Inorganic Components and Acidity of PM2.5 in a Coastal City of China

Xin Wu¹^,2^,3, Junjun Deng¹^,2, Jinsheng Chen ¹^,2, Youwei Hong¹^,2, Lingling Xu¹^,2, Liqian Yin¹^,2, Wenjiao Du¹^,2^,3, Zhenyu Hong¹^,2^,3, Nanzhen Dai¹^,2^,4, Chung-Shin Yuan⁵

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¹Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
²Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
³University of Chinese Academy of Sciences, Beijing 100049, China
⁴College of Environment and Resources, Fuzhou University, Fuzhou 350116, China
⁵Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan

Received: November 28, 2016
Revised: March 29, 2017
Accepted: May 17, 2017
Download Citation: ||https://doi.org/10.4209/aaqr.2016.11.0513

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Cite this article:
Wu, X., Deng, J., Chen, J., Hong, Y., Xu, L., Yin, L., Du, W., Hong, Z., Dai, N. and Yuan, C.S. (2017). Characteristics of Water-Soluble Inorganic Components and Acidity of PM2.5 in a Coastal City of China. Aerosol Air Qual. Res. 17: 2152-2164. https://doi.org/10.4209/aaqr.2016.11.0513

HIGHLIGHTS

Contributions and concentrations of sea-salt aerosol acidity were quantified.
Acidity of PM_2.5 in harbor site in summer was the highest.
Poor ammonium in PM_2.5 mainly combined with sulfate as the form of NH₄HSO₄.

ABSTRACT

To investigate the characteristics of water-soluble inorganic ions (WSIIs) of PM_2.5 and aerosol acidity in a coastal city, 352 samples were collected at four sites representing four functional zones (FJ: living town; XY: industrial area; TZ: scenery areas; HR: harbor) in Xiamen, China in 2015–2016. Mass concentrations of PM_2.5, nine WSIIs, total acidity and in-situ acidity of aerosol/non-sea-salt aerosol were measured. Overall, the mean mass concentrations of PM_2.5 in the study area in spring, summer, autumn and winter were 57.5 ± 22.3, 28.1 ± 12.6, 46.8 ± 18.3 and 62.4 ± 22.1 µg m^–3, respectively. WSIIs accounted for 36%–56% of PM_2.5 at four sites. Secondary ions (non-sea-salt SO₄^2–, NO₃^– and NH₄⁺) contributed more than 74% to total WSIIs. Neutralization degree distributions indicated that 79.5% of PM_2.5 was acidic. Total acidity and in-situ acidity both showed obvious seasonal variations, exhibited the peak values of 193.20 and 130.17 nmol m^–3 at HR site in summer. Sea-salt contributed 2.58%–17.74% to acidity in four seasons. The normalized ammonium concentration ([NH₄⁺]/[SO₄^2–]) and normalized nitrate concentration ([NO₃^–]/[SO₄^2–]) showed greater correlation coefficients after eliminating the ammonium-poor data points (greater than 0.66), especially at HR site. NH₄HSO₄ was the major form of WSIIs in PM_2.5 and the formation of aqueous HNO₃ could enhance aerosol acidity.