Fossil and Non-fossil Sources of Organic and Elemental Carbon Aerosols in Beijing, Shanghai and Guangzhou: Seasonal Variation of Carbon Source

Abstract. Fossil fuel (FF) combustion and biomass burning are the two most important contributors to the highly polluted air in China. Given that the large territorial area of China, it is interesting to know how these two emission sources exert influences on carbonaceous particles over megacities in different regions and different seasons. Here, the radiocarbon (14C) isotopic signals are reported in Beijing, Shanghai and Guangzhou, China from 2013 to 2014. Generally, a greater contribution of non-fossil (NF) (> 55 %) source was found in all cities in autumn. However, the source seasonality was different among the cities in other seasons. In winter, FF contributed the most in Beijing (64 %), NF contributed the most in Guangzhou (63 %), and FF contributed slightly more than NF in Shanghai (54 %). In spring and summer, Beijing and Guangzhou were similar to each other with a higher contribution of FF (55 % and 63 %, respectively) than NF. FF had the highest contribution (71 %) in Shanghai in summer. Comparison of carbon sources between haze and non-haze periods suggests that the carbon sources in each season are almost consistent. Secondary organic carbon (SOC) mainly originated from biomass burning and vehicle emissions, except in Beijing in winter when the major source was residual coal combustion.