Speciation and Photochemistry of Nitrogen Oxides Adsorbed to Environmentally Relevant Surfaces
EMSL Project ID
34912
Abstract
The overall goal of this research is to elucidate the mechanism of HONO formation by the photolysis of adsorbed-NOy (NOy = NO + NO2 + HNO3 + N2O5 + ...) species on environmentally relevant surfaces under ambient conditions using a variety of surface analysis techniques [Fourier transform infrared spectroscopy coupled mass spectrometry (FTIR / MS), temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and time-of-flight secondary ion mass spectrometry (TOF-SIMS)] uniquely available at EMSL. In the lower atmosphere nitrous acid is a major photolytic source of the highly reactive OH free radical, which plays a crucial role in both removing organic pollutants in the atmosphere and initiating chemical reactions that cause air pollution events. It is thought that HONO comes from the interaction of NO2 with surfaces (airborne particles/droplets or ground-level surfaces) and its formation appears to be photolytically enhanced. However, the chemical mechanism of this photochemical process remains a mystery due to analytical challenges in observing reactive species adsorbed to surfaces. This project is sponsored by the National Science Foundation's American Competitiveness in Chemistry Postdoctoral Fellowship program and will form the basis of a collaboration between the users from University of California Irvine and scientists at EMSL to study a problem of critical importance to atmospheric chemistry using resources unavailable outside PNNL. Studies on the interactions of NOy with aerosol and environmentally important surfaces (e.g. those found on urban infrastructure, vegetation, soils, etc.) will help us understand changes in compositions of these surfaces during atmospheric "aging" and the ability of these surfaces to act as sinks for NOy and to affect the oxidative capacity of the atmosphere. Fundamental surface studies carried out at EMSL will provide a molecular-level understanding of the mechanisms that control speciation and photochemistry of adsorbed NOy on oxide and organic surfaces and will have far-reaching implications not only for atmospheric chemistry, but also for understanding corrosion processes and in designing of catalytic systems used in air pollution control technologies.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2009-10-01
End Date
2011-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Raff JD, J Szanyi, and BJ Finlayson-Pitts. 2011. "Thermal and photochemical oxidation of self-assembled monolayers on alumina particles exposed to nitrogen dioxide." PNNL-SA-77584, Pacific Northwest National Laboratory, Richland, WA.