Index Geophysics

Measurements of gaseous H2SO4 by AP-ID-CIMS during CAREBeijing 2008 Campaign

As part of the 2008 Campaign of Air Quality Research in Beijing and Surrounding Regions (CAREBeijing 2008), measurements of gaseous sulfuric acid (H₂SO₄) have been conducted at an urban site in Beijing, China from 7 July to 25 September 2008 using atmospheric pressure ion drift – chemical ionization mass spectrometry (AP-ID-CIMS). This represents the first gaseous H₂SO₄ measurements in China. Diurnal profile of sulfuric acid is strongly dependent on the actinic flux, reaching a daily maximum around noontime and with an hourly average concentration of 5 &times; 10⁶ molecules cm⁻³. Simulation of sulfuric acid on the basis of the measured sulfur dioxide concentration, photolysis rates of ozone and nitrogen dioxide, and aerosol surface areas captures the trend of the measured H₂SO₄ diurnal variation within the uncertainties, indicating that photochemical production and condensation onto preexisting particle surface dominate the observed diurnal H₂SO₄ profile. The frequency of the peak H₂SO₄ concentration exceeding 5 &times; 10⁶ molecules cm⁻³ increases by 16 % during the period of the summer Olympic Games (8–24 August 2008), because of the implementation of air quality control regulations. Using a multivariate statistical method, the critical nucleus during nucleation events is inferred, containing two H₂SO₄ molecules (<i>R</i>² = 0.85). The calculated condensation rate of H₂SO₄ can only account for 10–25 % of PM₁ sulfate formation, indicating that either much stronger sulfate production exists at the SO₂ source region or other sulfate production mechanisms are responsible for the sulfate production.

Zheng, J.

Hu, M.

Zhang, R.

Yue, D.

Wang, Z.

Guo, S.

Li, X.

Bohn, B.

Shao, M.

He, L.

Huang, X.

Wiedensohler, A.

Zhu, T.

2018-01-15

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application/pdf

10.5194/acp-11-7755-2011

https://acp.copernicus.org/articles/11/7755/2011/

eISSN: 1680-7324

eng