10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Chemical Composition of PM2.5 in Zion, IL during the 2017 Lake Michigan Ozone Study
DAGEN HUGHES, Alissia Milani, Megan Christiansen, Dylan Millet, Timothy Bertram, Charles Stanier, Elizabeth Stone, University of Iowa
Abstract Number: 600 Working Group: Aerosol Chemistry
Abstract Areas along the coast of Lake Michigan are consistently in violation of federal air quality standards for ozone. The enhancement of ozone during the springtime and summertime is thought to result from the unique meteorology of coastal regions. In a collaborative effort to better understand ozone production over Lake Michigan, the Lake Michigan Ozone Study (LMOS 2017) took place from May 21 to June 23, 2017, combining airborne, ship, mobile lab, and fixed ground based measurements. Here, we focus on identifying the major sources contributing to fine particulate matter (PM2.5) in Zion, Illinois so that the sources contributing to ozone formation can be better understood. Elemental and organic carbon (EC and OC), inorganic ions, organic molecular markers, and metals were quantified in daytime (08:00—20:00) and nighttime (20:30—07:30) ambient PM2.5 samples. PM2.5 mass concentration ranged from 1.2 – 11.5 µg/m3 with an average concentration of 5.3 µg/m3. OC levels ranged from <0.5 – 4.7 µg/m3 (averaging 4.7 µg/m3) while EC ranged from <0.05 – 0.8 µg/m3 (averaging 0.22 µg/m3). The average OC:EC ratio was 12.25, suggesting a large contribution from secondary organic aerosol. The most significant contributor to PM2.5 mass was organic matter (OM, calculated as 1.7 x OC, contributing 57.9%), followed by sulfate (16.4%), ammonium (6.3%), and nitrate (3.5%). Ozone concentrations exceeded the federal ozone standard of 70 ppb during a high-ozone event on June 02 and during a high-ozone period occurring from June 10 to June 16 where ozone concentrations reached 91 ppb and 88 ppb, respectively. The highest daily average of PM2.5 mass occurred during the high-ozone event (10.7 µg/m3) and was also elevated during the high-ozone period (6.7 µg/m3) as compared to non-event periods (4.6 µg/m3). The OC:EC ratio during the June 02 high-ozone event was 7.0—substantially lower than the ratios for the high-ozone period (13.8) and non-event periods (12.0)—suggesting a larger contribution from combustion emissions (higher EC) on this day. The measured species will be used with positive matrix factorization in order to determine sources contributing to fine particulate matter in Zion, IL, with an emphasis on understanding the distribution of primary/secondary and biogenic/anthropogenic sources.