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

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 (delta C-13) varied from -26.90 parts per thousand, to -23.08 parts per thousand for OC and -26.63 parts per thousand, to -23.27 parts per thousand for EC. A strong correlation (R-2 = 0.70, p < 0.0001) between delta C-13(OC) and delta C-13(EC) was found in winter but not summer. Winter vs. summer differences for delta C-13(OC) and delta C-l3(EC) were greater for the seven northern cities (similar to 1 to 3 parts per thousand) than the seven southern cities (<1 parts per thousand). 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. (C) 2010 Elsevier Ltd. All rights reserved.