AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
How To Achieve Further PM2.5 Reductions in a Midwestern City? A Combined Modeling and Measurement-Based Analysis of Iowa City, IA
ROBERT BULLARD, Elizabeth Stone, Charles Stanier, Ashish Singh, Can Dong, Chathurika Rathanyake, Thilina Jayarathne, Scott N. Spak, University of Iowa
Abstract Number: 211 Working Group: Urban Aerosols
Abstract The Iowa City, IA metropolitan area has regionally representative annual average PM$_(2.5) concentrations, with levels measured by the local EPA monitor ranging 10-12 micrograms/m$^3 in recent years. However, this monitor is located 3.5 km from the downtown area, which has the highest population density and pedestrian exposure to air pollutants. The downtown also includes a majority of anthropogenic emissions from vehicles, cooking, local power generation, and medical waste incineration. To better understand population exposure to air pollution, we (a) chemically characterized PM$_(2.5); (b) evaluated the absolute and relative impacts of electric generation, industry, motor vehicles, residential emissions, and regional transport using CMB and chemical transport modeling (CTM); and (c) used the CTM with high resolution (0.4 km) emissions to generate spatially-resolved concentration maps of PM$_(2.5), O$_3, and their precursors.
In 2011 and 2012, PM$_(2.5) samples were collected and analyzed for organic and elemental carbon (OC and EC), inorganic ions, and molecular markers at two locations. OC and EC averaged 2.5 and 0.3 micrograms/m$^(3), respectively, and exhibited seasonal patterns. Particle phase polycyclic aromatic hydrocarbons and the coal tracer picene peaked in winter. CMB modeling indicated that biomass burning and then non-catalyzed gasoline engines were the greatest contributors to primary PM$_(2.5) OC. The downwind site was enhanced in tracers for coal combustion tracer (factor of ~3), biomass burning (factor of ~1.5), and motor vehicles (factor of ~1.3). A two-week mobile field study was conducted to measure the aerosol concentration, aerosol size distribution, NO$_x, and SO$_2 concentrations in the power plant plume. Under breezy summer conditions, the plume contained about 10 ppb each of NO, NO$_2, and SO$_2, when it reached ground level in downtown Iowa City, and high concentrations of ultrafine particles. High resolution (0.4 km) WRF-CMAQ model was run for one year corresponding to the filter sampling period.