AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Spatial and Seasonal Variation in the Molecular Composition of the Humic-Like-Substances (HULIS) Fraction of Ambient Aerosols: Clue for the Sources of Aerosol Oxidative Potential
YING WANG, Vishal Verma, Ting Fang, Rodney Weber, Georgia Institute of Technology
Abstract Number: 490 Working Group: Linking Aerosols with Public Health in a Changing World
Abstract Atmospheric Humic-like substances (HULIS) are an operationally defined, polar, acidic and chromophoric material, isolated from ambient aerosols or fog and cloud samples.They are ubiquitously present in the troposphere and make up a major fraction of the continental fine-sized water-soluble organic compounds (WSOC). HULIS is often regarded as a complex mixture of organic compounds. However, structural information at the individual component level is rather limited. Recent studies also show that HULIS is closely associated with the production of reactive oxygen species (ROS) in aerosols which is known to exert oxidative stress via inhalation.
In the present study, we characterized the HULIS fraction from different locations and seasons using gas chromatography mass spectrometry (GC-MS). Aerosol samples with an aerodynamic diameter of 2.5 microns or less (PM2.5) were collected using High Volume samplers at an urban site, a rural site and a highway site around Atlanta, Georgia, during the period of June 2012 to April 2013. High volume quartz-fibers filters were extracted by water and passed through C-18 columns to separate the HULIS fraction. Hydrophobic compounds retained on the column were eluted by methanol and analyzed by GC-MS. The chromatographs are dominated by multifunctional hydroxyl and carbonyl compounds. Biomass burning biomarkers, including monosaccharide derivatives such as levoglucosan, are prominent in winter urban sites. Secondary aerosol compounds derived from terpenoids are found to be widely present in HULIS with compound types varying with seasonality. These variations in HULIS molecular composition provide useful information on the sources of organic aerosols in different seasons in southeast US. The possible contribution of these HULIS compounds to aerosol oxidative potential would be further investigated by correlating the compound concentrations with the ROS generation capability of these samples which was analyzed in a previous study using a dithiothreitol (DTT) assay.