Production of Secondary Organic Aerosol from Multiphase Terpene PhotooxidationEPA Grant Number: R833750
Title: Production of Secondary Organic Aerosol from Multiphase Terpene Photooxidation
Investigators: Shepson, Paul
Institution: Purdue University
EPA Project Officer: Chung, Serena
Project Period: November 1, 2007 through October 31, 2010 (Extended to October 31, 2011)
Project Amount: $333,397
RFA: Sources and Atmospheric Formation of Organic Particulate Matter (2007) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air
This project involves a field and laboratory study of the production of aerosol from the atmospheric photooxidation of biogenic volatile organic compounds (BVOCs), specifically the terpenes α- and β-pinene, using a unique combination of approaches that rely on product analysis via mass spectrometry, aerosol measurement instruments, and desorption electrospray ionization methods.
The objective of this research is to improve our quantitative and mechanistic understanding of the mechanisms for production of secondary organic aerosol, an important type of air pollutant, from the atmospheric oxidation of α- and β-pinene. We aim to determine product yields for major gas phase OH- and O3-induced oxidation products with much smaller uncertainty bounds than have previously been reported, thereby improving the capability of air quality models that simulate aerosol production from BVOCs. We will study the oligomerization of aerosol phase species, and study the extent to which photochemistry in aerosols and in cloud water contributes to secondary organic aerosol production. A main hypothesis for this study is thus: Aerosol can age both as a result of polymerization chemistry, but also because of aerosol-phase photochemistry, and this processing influences the distribution of species between the gas and aerosol phase. The information produced from the linked laboratory and field studies will be used to develop improved computer model modules that describe secondary organic aerosol from these important terpenes.
The proposed objectives will be realized through a unique combination of laboratory photochemical reaction chamber studies and field measurements of the pinene reaction products and aerosol growth above forest environments. This project will rely on an extensive array of state of the art analytical and experimental resources, including an all-Teflon photochemical reaction chamber, a Proton Transfer Reaction Linear Ion Trap (PTRLIT) for product identification and quantitation, and the Purdue Airborne Laboratory for Atmospheric Research (ALAR) aircraft. The objectives will be pursued through 1. PTRLIT and GC/MS measurements of reactants and products during reaction chamber pinene/NOx irradiations, and pinene-O3 experiments; 2. analysis of aerosol-phase organics using the highly powerful Desorption-ElectroSpray-Ionization (DESI)-MS technique; 3. DESI-MS analysis of cloud water samples from above forest environments that are aged and irradiated in the laboratory; 4. Measurements of the oxidation products nopinone and pinonaldehyde, along with rates of aerosol growth in a Michigan forest environment, to investigate the fraction of SOA growth derived from α- and β-pinene in such environments.
From the results of this work we will develop new chemical mechanism reaction modules to be incorporated into both the gas and aerosol phase components of community model systems including the Community Multiscale Air Quality Model (CMAQ). This project aims to better link the gas and aerosol chemistry modules to more accurately reflect photochemistry in both phases, and mass transfer between phases.