Contributions of Fossil Fuel Combustion to Winter-time Arctic Aerosols
Monday, 15 December 2014
Over the last century, the Arctic has been warming at a rate almost twice the global average. Aerosols both directly and indirectly affect the radiative balance of the Arctic through the absorption and scattering of sunlight and by providing a source of cloud and ice condensation nuclei. Global climate models currently have difficulty reproducing the observed warming in the Arctic but could be improved through high temporal resolution measurements of aerosols and their sources. This study focuses on the quantification of fossil fuel and biomass combustion contributions to particulate organic carbon (OC) collected during a winter sampling campaign in the North Slope Alaska. Samples were collected at the Department of Energy Atmospheric Radiation Measurement (ARM) climate research facility in Barrow, AK, USA. Particulate matter (PM10) samples collected from December 2012 to March 2013 were analyzed for organic tracer analysis combined with radiocarbon of elemental and organic carbon (EC and OC). Organic tracers, including polycyclic aromatic hydrocarbons (PAHs), alkanes, hopanes and levoglucosan, were quantified using gas chromatography-mass spectrometry (GCMS). These tracers, commonly used as molecular markers for anthropogenic combustion sources, were then used in a molecular-marker chemical mass balance (CMB) model. Results from the CMB were then combined with radiocarbon (14C) abundance measurements. Radiocarbon analysis differentiates between fossil fuel combustion and biomass burning based on the large difference in end members between fossil and contemporary carbon. Radiocarbon results show an average fossil contribution of 44% to Arctic OC from with spark ignition (gasoline) and compression ignition (diesel) engines being implicated as major sources of fossil OC to Arctic aerosols. The 14C analysis and CMB source apportionment will be combined with back trajectory (BT) to assess the impact of geographic source regions on carbonaceous aerosol burden in the Arctic.