Secondary aerosols are formed through atmospheric reactions and the partitioning of reaction products to the aerosol phase.  Precursors to secondary aerosol include inorganic gases such as ammonia (NH3), nitrous oxides (NOx), sulfur dioxide (SO2), and volatile organic compounds (VOC).  To investigate the impacts of local sources on secondary aerosol in the Midwest, fine particulate matter samples (PM2.5-) were collected at two locations on west and east sides Iowa City, IA from August 25 to November 10, 2011.  Filter samples were analyzed for organic and elemental carbon, inorganic ions, organic molecular markers, and secondary organic aerosol (SOA) tracers.  Combustion sources (namely vehicles and biomass burning) impacted the two sites to different extents, particularly on days with heightened local activities.  Ammonium, sulfate, and SOA peaked under hot and dry conditions and southerly winds at both sites.  Meanwhile, ammonium nitrate was enhanced during cooler temperatures and was and more spatially variable in the autumn indicative of local influences. A large-scale tire fire at the Iowa City landfill from May 26 to June 10, 2012 was a major source of aromatic and biogenic VOC, SO2, and NOx to the atmosphere and provided the opportunity to evaluate changes to SOA formation from isoprene and monoterpenes in response to high and low-NOx conditions in situ.

Point source impacts on secondary aerosol formation in the Midwestern United States

248th National Meeting (2014)

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