The Department of Civil and Environmental Engineering is pleased to announce Melissa Roskamp's MS Thesis Defense: "Characterization of Secondary Organic Aerosol Precursors Using Two-Dimensional Gas Chromatography with Time of Flight Mass Spectrometry (GC×GC/TOFMS)."
Date: Friday, June 14, 2013
Location: Engineering Building 315
Adviser: Dr. Kelley Barsanti
During the last 10 years, the importance with which the scientific community views secondary organic aerosol (SOA) has grown rapidly. Recent measurements indicate that organic fine particulate matter (PM2.5) is largely, and in some cases entirely, secondary. Writing in the New York Times on the health aspects of PM2.5 in February of last year, Barringer stated:
“[fine particles] kill an estimated 50,000 Americans each year. But more recently, scientists have been puzzled to learn that a subset of these particles, called secondary organic aerosols, has a greater total mass, and is thus more dangerous than previously understood.”(February12, 2012, http://www.nytimes.com/2012/02/19/science/earth/)
SOA is formed in the atmosphere through the oxidation of volatile organic compounds (VOCs). Each year, more than 1000TgC of non-methane VOCs are emitted from biogenic sources (significantly greater than from anthropogenic sources). Despite this magnitude and potential importance for air quality, the body of knowledge around the identities, quantities and oxidation processes of these compounds is still incomplete (e.g., Goldstein & Galbally, 2007; Robinson et al., 2009). Two-dimensional gas chromatography paired with time-of-flight mass spectrometry (GC×GC/TOFMS) is a powerful analytical technique which is explored here for its role in better characterizing biogenic VOCs (BVOCs) and thus SOA precursors.
This work presents measurements of BVOCs collected during two field campaigns and analyzed using GC×GC/TOF-MS. The first campaign, the Bio-hydro-atmosphere Interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen - Rocky Mountain Biogenic Aerosol Study (BEACHON-RoMBAS), took place in a Ponderosa pine forest in Colorado. The second campaign, Particle Investigations at a Northern Ozarks Tower: NOx, Oxidant, Isoprene Research (PINOT NOIR) Study, was conducted in the Ozark region of Missouri. Tens to hundreds of BVOCs were quantified in each set of samples, including primary emissions, atmospheric oxidation products, stress indicators and semi-volatile leaf surface compounds. These findings highlight that there is a largely uncharacterized diversity of BVOCs in ambient samples. Our findings demonstrate that GC×GC can distinguish between compounds with the same molecular weight and similar structure, which have highly variable potentials for production of SOA (Lee et al., 2006). This work represents some of the first analysis of ambient BVOCs with this technology, which we anticipate will contribute greatly to characterization of atmospheric SOA precursors and ultimately, regional and global modeling of SOA and fine particulate matter.