Impact of environmental variables on the reduction of nitric acid (HNO3) by volatile organic compounds emitted by motor vehicles

Authors

Y J. Leong, Rice University
A P. Rutter, Rice University
C V. Gutierrez, Rice University
Hui Yi Wong, Rice University
Mariam Junaid, Rice University
Eric Scheuer, University of New Hampshire - Main CampusFollow
Jack E. Dibb, University of New HampshireFollow
R J. Griffin, Rice UniversityFollow

Abstract

Nitric acid (HNO₃) has long been thought of as a sink for nitrogen oxides in the atmosphere but recently has been identified as a potential precursor of nitrous acid (HONO). The mechanisms proposed for the conversion of HNO₃ to HONO included heterogeneous reactions on surfaces such as primary organic aerosols, vegetation, and glass. Recent work in our laboratory has indicated that the reduction of HNO₃ to HONO occurs homogeneously in the presence of volatile organic compounds (VOCs) emitted by motor vehicles. These experiments were conducted using a temperature-controlled quartz flow-tube reactor, and measurements of HNO₃ and HONO were collected using a mist-chamber/ion-chromatography system. The average observed HONO formation rate was 0.54 ± 0.08 ppb hr^-1 at 25 °C and ~20% relative humidity; these data are comparable to data from a 2006 field study in Houston, TX during which enhancements in HONO during morning rush hour were observed. This study focuses on the impact of environmental variables on the rate of formation of HONO. This rate decreases at higher relative humidity but increases with decreasing reactor temperature. The reaction rate does not change when initial HNO₃ concentration is varied between 400 to 4600 ppt, suggesting that the concentration of reactive VOCs was the limiting factor. The reduction of HNO₃ to HONO appears not to occur heterogeneously on the aerosol surfaces tested (motor oil, alumina, and carboxylated silica aerosol). The presence of ~120 ppb of ammonia has no observable impact on the reaction. The homogeneous conversion of HNO₃ to HONO can have significant atmospheric implications due to the “renoxification” of non-reactive HNO₃ into the reactive nitrogen species HONO.

Department

Earth Sciences, Earth Systems Research Center

Publication Date

Fall 2014

Journal Title

Abstracts of Papers of the Aamerican Chemical Society

Publisher

American Chemical Society

Document Type

Conference Proceeding

Recommended Citation

Leong, Y J.; Rutter, A P.; Gutierrez, C V.; Wong, Hui Yi; Junaid, Mariam; Scheuer, Eric; Dibb, Jack E.; and Griffin, R J., "Impact of environmental variables on the reduction of nitric acid (HNO3) by volatile organic compounds emitted by motor vehicles" (2014). Abstracts of Papers of the Aamerican Chemical Society. 121.
https://scholars.unh.edu/earthsci_facpub/121

Comments

0065-7727