Elevated nitrogen-containing particles observed in Asian dust aerosol samples collected at the marine boundary layer of the Bohai Sea and the Yellow Sea

H Geng,H Hwang,Y Park,S Kang,C.-U Ro

doi:10.5194/acp-9-6933-2009

Abstract

Abstract. Low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA) shows powerful advantages for the characterization of ambient particulate matter in environmental and geological applications. By the application of the low-Z particle EPMA single particle analysis, an overall examination of 1800 coarse and fine particles (aerodynamic diameters: 2.5–10 μm and 1.0–2.5 μm, respectively) in six samples collected on 28 April–1 May 2006 in the marine boundary layer (MBL) of the Bohai Sea and Yellow Sea was conducted. Three samples (D1, D2, and D3) were collected along the Bohai Bay, Bohai Straits, and Yellow Sea near Korea during an Asian dust storm event while the other three samples (N3, N2, and N1) were collected on non-Asian dust (NAD) days. Based on X-ray spectral and secondary electron image data, 15 different types of particles were identified, in which soil-derived particles were encountered with the largest frequency, followed by (C, N, O)-rich droplets (likely the mixture of organic matter and NH4NO3), particles of marine origin, and carbonaceous, Fe-rich, fly ash, and (C, N, O, S)-rich droplet particles. Results show that during the Asian dust storm event relative abundances of the (C, N, O)-rich droplets and the nitrate-containing secondary soil-derived particles were markedly increased (on average by a factor of 4.5 and 2, respectively in PM2.5−10 fraction and by a factor of 1.9 and 1.5, respectively in PM1.0−2.5 fraction) in the MBL of the Bohai Sea and Yellow Sea, implying that Asian dust aerosols in springtime are an important carrier of gaseous inorganic nitrogen species, especially NOx (or HNO3) and NH3.

Highlights

The Asian dust storm event is a seasonal meteorological phenomenon that mostly originates in the deserts of Mongolia and Northern China and Kazakhstan (Sullivan et al, 2007)
Note: Samples N1, N2, and N3 were collected on non-Asian dust (NAD) days while D1, D2, D3 were collected during an Asian dust storm event
The results suggest that airborne NOx rather than SO2 is prone to react with the primary supermicron alminosilicate, SiO2, and CaCO3 particles; or, the mass concentration of NOx in the marine boundary layer (MBL) of the Yellow Sea might be higher than the mass concentration of SO2

Summary

Introduction

The Asian dust storm event is a seasonal meteorological phenomenon that mostly originates in the deserts of Mongolia and Northern China and Kazakhstan (Sullivan et al, 2007). Asian dust aerosols can react with a diversity of chemical species, coagulate with other particles, and/or provide reaction sites in the atmosphere, so that they potentially carry many chemical species along with the original soil components, and the physical and chemical properties of the dust particles may change (Hwang et al, 2008). These change/coagulation processes affect the optical and hygroscopic properties of Asian dust particles, which are related to important but uncertain direct impacts on climate change, radiative budget, and possibly rainfall patterns (Ramanathan, et al, 2001; Jickells et al, 2005; Su et al, 2008), and they affect the cycles and chemical balances of important trace gases (e.g. SO2, NOx, O3), acid deposition, and the pH of precipitation (Sullivan et al, 2007).

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