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 (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.