Determination of the Sulfur Mass Balance in Isoprene Epoxydiol-Derived Secondary Organic Aerosols
REBECCA TURNER, Tracy Dombek, N. Cazimir Armstrong, Adam Conway, Barbara Turpin, Zhenfa Zhang, Avram Gold, Andrew P. Ault, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 545
Working Group: Aerosol Processes and Properties in Changing Environments in the Anthropocene
Abstract
Isoprene epoxydiols (IEPOX), major atmospheric oxidation products of the abundant biogenic VOC isoprene, contribute extensively to secondary organic aerosol (SOA) formation in Earth’s troposphere in low-NOx regions. IEPOX undergoes acid-catalyzed multiphase chemical reactions with anthropogenically derived acidic sulfate aerosol particles, forming a variety of low-volatility and semivolatile SOA products. One class of low-volatility SOA products is organosulfates (OS), which result from inorganic sulfate covalently bonded with IEPOX upon its epoxide-ring opening reactions. However, the mass balance between inorganic sulfate OS has yet to be constrained by laboratory studies under varying aerosol acidity conditions representative of atmospheric aerosols.
In this study, smog chamber experiments were conducted to constrain the mass balance between organic and inorganic sulfur. The SOA formed during these experiments were collected onto filters and subsequently chemically analyzed with ion chromatography (IC) and inductively coupled plasma interfaced to optical emission spectroscopy (ICP-OES) to determine the change in sulfur form before and after reaction with IEPOX. From our initial results, the percentage of inorganic sulfate converted to OS in IEPOX-derived SOA is approximately 47.1 to 50.2%. Methyltetrol sulfates, the most abundant form of OS found in atmospheric aerosols, will be quantified by HILIC/ESI-HR-QTOFMS, allowing for the first determination of the total mass fractions of oligomeric OS.
This work will help atmospheric modelers in their predictions of SOA formation and sulfur mass balance in atmospheric aerosols, which has not been well constrained by models thus far. Ongoing work will include further constraining the effect of initial IEPOX: inorganic sulfate mass ratio at a fixed aerosol acidity on the particulate sulfur mass balance in chamber experiments.