Characterization of Atmospheric Organic and Elemental Carbon of PM2.5 in a Typical Semi-Arid Area of Northeastern China

Renjian Zhang,Leiming Zhang,K.F Ho,Suixin Liu,Gehui Wang,Jun Tao,Zhenxing Shen,Junji Cao,S.C Lee

doi:10.4209/aaqr.2011.07.0110

Abstract

ABSTRACTIn the spring of 2006, daily particulate matter (PM2.5) aerosol samples were collected in Tongyu, a semi-arid area in northeastern China. The concentrations of organic carbon (OC) and elemental carbon (EC) were determined with a thermal/optical carbon analyzer in the filter samples. The average concentrations of OC and EC in PM2.5 were 14.1 ± 8.7 and 2.0 ± 1.3 μg/m3, respectively. A good correlation between OC and EC was observed during the spring season, suggesting that they might be derived from similar sources. The correlation between OC and K+ was high (R = 0.74), and the K+/OC ratio, as determined from their linear regression slope, reached 2.57. The good correlation and high K+/OC ratio indicated that biomass-burning was probably one of the major sources of OC in this region. The concentrations of estimated secondary organic carbon (SOC) in PM2.5 in Tongyu ranged from below the detection limit to 26.1 μg/m3 (mean, 5.9 μg/m3). The percentages of SOC in OC and in PM2.5 mass were 42.0% and 2.1%, respectively. The SOC concentrations during dust storm (DS) periods were higher than those during non-dust storm (NDS) ones, suggesting that chemical reaction processes involving gas-particle conversion occurred during the long-distance transport of aerosol particles.

Highlights

A good correlation between organic carbon (OC) and elemental carbon (EC) was observed during the spring season, suggesting that they might be derived from similar sources
Where OCsec is the secondary OC (SOC), OCtotal is the total OC (TOC), and (OC/EC)min is the minimum ratio of OC to EC concentration monitored
The major challenge in this method is the accuracy of (OC/EC)min since it could be influenced by meteorological conditions and emission fluctuations

Summary

Introduction

Carbonaceous materials, including organic carbon (OC) and elemental carbon (EC), are major components of ambient aerosols in urban and rural atmospheres (He et al, 2001; Wang et al, 2001; Cao et al, 2004; Duan et al, 2005; Chen and Yu, 2007) and play important roles on radiative transfer, health effects, and atmospheric chemistry (Andreae, 1983; Crutzen and Andreae, 1990; Menon et al, 2002; Wu et al, 2004; Zhang et al, 2009). The concentrations of estimated secondary organic carbon (SOC) in PM2.5 in Tongyu ranged from below the detection limit to 26.1 μg/m3 (mean, 5.9 μg/m3). The SOC concentrations during dust storm (DS) periods were higher than those during non-dust storm (NDS) ones, suggesting that chemical reaction processes involving gas-particle conversion occurred during the long-distance transport of aerosol particles.

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Conclusion