Post Date: 1 December 2014

Fossil vs. non-fossil sources of fine carbonaceous aerosols in four Chinese cities during the extreme winter haze episode in 2013

Abstract

Carbonaceous aerosols, which comprise the large fractions of elemental carbon (EC) and organic carbon (OC), badly affect climate and human health. However, there is a large uncertainty about detailed apportionment and quantification of its sources due to the large number of origins and chemical compounds associated with the aerosols. Radiocarbon (¹⁴C) measurements provide a powerful tool for unambiguously determining fossil and non-fossil sources of carbonaceous particles, since ¹⁴C is completely depleted in fossil-fuel emissions due to its age, whereas non-fossil carbon sources (e.g. biomass burning, cooking or biogenic emissions) show a contemporary ¹⁴C content. Moreover, a better 14C-based source apportionment can be obtained, when ¹⁴C determinations are performed on EC and OC/TC separately, since EC originates exclusively from combustion of biomass and fossil fuels. In this study, PM_2.5 aerosol samples are collected at four large cities in China during winter 2013. EC and OC, ¹⁴C and biomass burning markers are used in conjunction with an effective statistical approach (i.e. Latin-hypercube sampling), allowing a quantitative source apportionment of fine carbonaceous aerosols. These sources include EC from combustion of biomass and fossil fuel, OC from fossil emissions including primary and secondary sources (as well as OC from non-fossil sources including primary biomass burning and all the other non-fossil OC.