Source apportionment of carbonaceous chemical species to fossil fuel combustion, biomass burning and biogenic emissions by a coupled radiocarbon–levoglucosan marker method

Abstract. An intensive aerosol measurement and sample collection campaign was conducted in central Budapest in a mild winter for 2 weeks. The online instruments included an FDMS-TEOM, RT-OC/EC analyser, DMPS, gas pollutant analysers and meteorological sensors. The aerosol samples were collected on quartz fibre filters by a low-volume sampler using the tandem filter method. Elemental carbon (EC), organic carbon (OC), levoglucosan, mannosan, galactosan, arabitol and mannitol were determined, and radiocarbon analysis was performed on the aerosol samples. Median atmospheric concentrations of EC, OC and PM_2.5 mass were 0.97, 4.9 and 25 µg m⁻³, respectively. The EC and organic matter (1.6  ×  OC) accounted for 4.8 and 37 %, respectively, of the PM_2.5 mass. Fossil fuel (FF) combustion represented 36 % of the total carbon (TC  =  EC + OC) in the PM_2.5 size fraction. Biomass burning (BB) was a major source (40 %) for the OC in the PM_2.5 size fraction, and a substantial source (11 %) for the PM₁₀ mass. We propose and apply here a novel, straightforward, coupled radiocarbon–levoglucosan marker method for source apportionment of the major carbonaceous chemical species. The contributions of EC and OC from FF combustion (EC_FF and OC_FF) to the TC were 11.0 and 25 %, respectively, EC and OC from BB (EC_BB and OC_BB) were responsible for 5.8 and 34 %, respectively, of the TC, while the OC from biogenic sources (OC_BIO) made up 24 % of the TC. The overall relative uncertainty of the OC_BIO and OC_BB contributions was assessed to be up to 30 %, while the relative uncertainty for the other apportioned species is expected to be below 20 %. Evaluation of the apportioned atmospheric concentrations revealed some of their important properties and relationships among them. EC_FF and OC_FF were associated with different FF combustion sources. Most EC_FF was emitted by vehicular road traffic, while the contribution of non-vehicular sources such as domestic and industrial heating or cooking using gas, oil or coal to OC_FF was substantial. The mean contribution of BB to EC particles was smaller by a factor of approximately 2 than that of road traffic. The main formation processes of OC_FF, OC_BB and OC_BIO from volatile organic compounds were jointly influenced by a common factor, which is most likely the atmospheric photochemistry, while primary organic emissions can also be important. Technological improvements and control measures for various BB appliances, together with efficient education and training of their users, in particular on the admissible fuel types, offer an important potential for improving the air quality in Budapest, and likely in other cities as well.