Abstract
Radiocarbon offers a unique possibility for unambiguous source apportionment of carbonaceous particles due to a direct distinction of non-fossil and fossil carbon. In this work, particulate matter of different size fractions was collected at 4 sites in Switzerland to examine whether fine and coarse carbonaceous particles exhibit different fossil and contemporary sources. Elemental carbon (EC) and organic carbon (OC) as well as water-soluble OC (WSOC) and water-insoluble OC (WINSOC) were separated and determined for subsequent 14C measurement. In general, both fossil and non-fossil fractions in OC and EC were found more abundant in the fine than in the coarse mode. However, a substantial fraction (∼20 ± 5%) of fossil EC was found in coarse particles, which could be attributed to traffic-induced non-exhaust emissions. The contribution of biomass burning to coarse-mode EC in winter was relatively high, which is likely associated to the coating of EC with organic and/or inorganic substances emitted from intensive wood burning. Further, fossil OC (i.e. from vehicle emissions) was found to be smaller than non-fossil OC due to the presence of primary biogenic OC and/or growing in size of wood-burning OC particles during aging processes. 14C content in WSOC indicated that the second organic carbon rather stems from non-fossil precursors for all samples. Interestingly, both fossil and non-fossil WINSOC concentrations were found to be higher in fine particles than in coarse particles in winter, which is likely due to primary wood burning emissions and/or secondary formation of WINSOC.
Highlights
Carbonaceous particles, which significantly contribute to the atmospheric particulate matter (PM), are of worldwide concern due to their effects on climate, human health, and visibility (Pöschl 2005; Highwood and Kinnersley 2006; Jimenez et al 2009)
14C-based source apportionment of carbonaceous particles was conducted for Elemental carbon (EC), organic carbon (OC), water-soluble OC (WSOC), and water-insoluble OC (WINSOC) in both the fine and coarse size fractions
OC was dominated by non-fossil sources, whereas EC was dominated by fossil emissions in both the fine and coarse mode for samples from all stations except for Roveredo, where intensive wood burning and inversion conditions occurred during the sampling period
Summary
Carbonaceous particles, which significantly contribute to the atmospheric particulate matter (PM), are of worldwide concern due to their effects on climate, human health, and visibility (Pöschl 2005; Highwood and Kinnersley 2006; Jimenez et al 2009) These particles vary in size with a mass median aerodynamic diameter from 10 μm. Based on epidemiological and toxicological studies (Nel 2005; Chang et al 2011), health impacts of fine particles in air are more adverse than coarse particles because they can penetrate deeper in the human respiratory system Understanding their sources and chemical compositions of both fine and coarse particles is highly important to establish separate regulations to control their emissions (Barmpadimos et al 2012)
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