Radiocarbon Analysis of Carbonaceous Aerosols: Recent Developments

Carbonaceous aerosols are a major fraction of airborne particulate matter. They contribute to climate and health effects of the total aerosol burden of the atmosphere by counteracting the current trend of global warming and inducing respiratory and cardiovascular diseases, respectively. In spite of this general importance, only little is known about composition and sources of carbonaceous aerosols. Analysis of the long-lived radioactive isotope 14C (radiocarbon) is a unique source apportionment tool: it unambiguously separates fossil from non-fossil sources, as 14C has completely decayed in fossil fuels, whereas modern materials have the contemporary radiocarbon level. A novel separation method was developed for the direct determination of 14C in organic carbon (OC) and elemental carbon (EC), two sub-fractions of total carbon (TC). The implementation of a gas ion source for measurement with accelerator mass spectrometry (AMS) made 14C analysis more simple and robust. Based on this technique, all major contributions to the carbonaceous aerosol can be identified, which originate from fossil-fuel, biomass-burning and biogenic emissions. A survey of results from different field campaigns is shown.