Evaluation on the role of sulfuric acid in the mechanisms of new particle formation for Beijing case

Z B Wang,M Hu,M Boy,J Zheng,T Nieminen,D L Yue,R Y Zhang,A Wiedensohler,Z J Wu

doi:10.5194/acp-11-12663-2011

Abstract

Abstract. New particle formation (NPF) is considered as an important mechanism for gas-to-particle transformation, and gaseous sulfuric acid is believed as a crucial precursor. Up to now few field-based studies on nucleation mechanisms and the role of sulfuric acid were conducted in China. In this study, simultaneously measurements of particle number size distributions and gaseous sulfuric acid concentrations were performed from July to September in 2008. Totally, 22 new particle formation events were observed during the entire 85 campaign days. The results show that in the case of both higher source and sink values, the result of the competition between source and sink is more likely the key limiting factor to determine the observation of NPF events in Beijing. The concentrations of gaseous sulfuric acid show good correlations with freshly nucleated particles (N3-6 and formation rates (J3 and J1.5. The power-law relationship between H2SO4 concentration and N3-6 or J is adopted to explore the nucleation mechanism. The exponents are showed a great range (from 1 to 7). More than half of the NPF events exhibit an exponent larger than 2.5. For these cases, the thermodynamic process works better than the activation or kinetic nucleation theories to explain the nucleation events in urban atmosphere of Beijing.

Highlights

New particle formation (NPF) and the subsequent particle growth have been observed in various environments all over the world (Kulmala et al, 2004; Holmes, 2007)
The pre-existing particles could act as a sink to capture for both, condensing vapors and newly formed particles, which could prevent the occurrence of NPF events
This paper focuses on the Beijing case of the NPF in the polluted urban environment

Summary

Introduction

New particle formation (NPF) and the subsequent particle growth have been observed in various environments all over the world (Kulmala et al, 2004; Holmes, 2007). The particle growth could affect the global climate system by scattering and absorption of solar radiation directly (Stier et al, 2007). These particles may act as CCN and ice nuclei (IN) and influence the climate system indirectly (Lohmann and Feichter, 2005). Gaseous sulfuric acid has been identified as a key component in the NPF process (Weber et al, 1995; Kulmala, 2003; Berndt et al, 2005; Fiedler et al, 2005) and proposed as a key component in many nucleation theories, such as binary, ternary or ion-induced nucleation (Korhonen et al, 1999; Weber et al, 1999; Yu and Turco, 2000; Napari et al, 2002; Vehkamaki et al, 2002).

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Conclusion