Elsevier

Atmospheric Environment

Volume 45, Issue 6, February 2011, Pages 1359-1363
Atmospheric Environment

Stable carbon isotopes in aerosols from Chinese cities: Influence of fossil fuels

https://doi.org/10.1016/j.atmosenv.2010.10.056Get rights and content

Abstract

Stable carbon isotope ratios were determined for the OC and EC fractions of PM2.5 collected from 14 Chinese cities in January and June/July of 2003. The period-averaged isotope values (δ13C) varied from −26.90‰ to −23.08‰ for OC and −26.63‰ to −23.27‰ for EC. A strong correlation (R2 = 0.70, p < 0.0001) between δ13COC and δ13CEC was found in winter but not summer. Winter vs. summer differences for δ13COC and δ13CEC were greater for the seven northern cities (∼1 to 3‰) than the seven southern cities (<1‰). Comparisons with isotopic signatures of putative sources suggest that the carbonaceous PM2.5 was mainly from fossil fuels, especially coal combustion and motor vehicle emissions; the northern cities in particular were strongly impacted by coal combustion during winter. Studies of stable carbon isotopes in OC and EC are potentially useful for identifying sources for carbonaceous PM2.5, and this approach may be a useful new tool for the study of air pollution.

Research highlights

► Stable carbon isotope ratios were determined for OC and EC in PM2.5 from Chinese cities. ► The isotopic signatures indicate that coal combustion and motor vehicle exhaust were the major sources for the carbonaceous aerosols. ► Stable carbon isotopes can be useful for distinguishing among major sources for carbonaceous PM2.5.

Introduction

Stable carbon isotopes (13C and 12C) have proven to be useful geochemical markers, and these isotopes were first applied to studies of air pollution beginning in the 1980s (e.g., Chesselet et al., 1981). Cachier et al., 1985, Cachier et al., 1986 used carbon isotopes and the ratio of elemental carbon (EC) to total carbon (TC) in aerosol particles to investigate emissions from biomass burning. More recent work (Ho et al., 2006, Huang et al., 2006, Fisseha et al., 2009) has explored the use of carbon isotopes in EC and organic carbon (OC) in source apportionment and atmospheric chemical transformation studies.

In the present study, stable carbon isotope abundances were determined for the OC and EC fractions of particulate matter with aerodynamic diameters less than 2.5 μm (PM2.5) from fourteen cities in China. The studies were conducted to (1) evaluate spatial variations and summer versus winter differences in carbonaceous PM2.5 and (2) identify the most probable sources for this material.

Section snippets

Sampling sites and sample collection

Fourteen cities, including several megacities, in China were selected to represent aerosol populations from economically developed and developing regions of the country; these cities covered most of the country’s non-mountainous urban regions (Fig. 1). The cities included seven in northern China: Beijing, Changchun, Jinchang, Qingdao, Tianjin, Xi’an, and Yulin; and seven in southern China: Chongqing, Guangzhou, Hong Kong, Hangzhou, Shanghai, Wuhan, and Xiamen. Detailed descriptions of these

Variations in the stable carbon isotope ratios of carbonaceous aerosols

Average δ13C values in OC, EC and TC during the two sampling periods are summarized in Table 1. δ13COC varied by 3.54‰ during winter from −26.62‰ in Hong Kong to −23.08‰ in Changchun and by 1.61‰ during summer from −26.90‰ in Beijing and Xi’an to −25.29‰ in Wuhan. Compared with δ13COC, the variations in δ13CEC were relatively small, differing by 2.83‰ during winter from −26.10‰ in Guangzhou to −23.27‰ in Changchun and by 1.36‰ in summer from −26.63‰ in Xiamen to −25.27‰ in Jinchang.

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Conclusions

Stable carbon isotope ratios were determined for OC and EC in PM2.5 from fourteen selected cities in China. The δ13COC values varied between −26.9‰ and −23.08‰ and δ13CEC varied between -26.63‰ and −23.27‰. The isotopic signatures indicate that coal combustion and emissions from motor vehicles were the major sources for the carbonaceous aerosols. The urban air in seven northern cities was strongly impacted by coal burned for residential heating during winter. Our results show that stable carbon

Acknowledgements

This work was supported by grants from the Chinese National Science Foundation (40925009) and as projects from the Chinese Academy of Sciences (KZCX2-YW-BR-10, KZCX2-YW-148) and the Ministry of Science and Technology (2009IM030100).

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