Sign up & Download
Sign in

Kinetics and mechanisms of heterogeneous reaction of NO2 on CaCO3 surfaces under dry and wet conditions

by H J Li, T Zhu, D F Zhao, Z F Zhang, Z M Chen
Atmospheric Chemistry and Physics ()

Abstract

With increasing NO2 concentration in the troposphere, the importance of NO2 reaction with mineral dust in the atmosphere needs to be evaluated. Until now, little is known about the reaction of NO2 with CaCO3. In this study, the heterogeneous reaction of NO2 on the surface of CaCO3 particles was investigated at 296 K and NO2 concentrations between 4.58x10(15) molecules cm(-3) to 1.68x10(16) molecules cm(-3), using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) combined with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), under wet and dry conditions. Nitrate formation was observed under both conditions, while nitrite was observed under wet conditions, indicating the reaction of NO2 on the CaCO3 surface produced nitrate and probably nitrous acid (HONO). Relative humidity (RH) influences both the initial uptake coefficient and the reaction mechanism. At low RH, surface -OH is formed through dissociation of the surface adsorbed water via oxygen vacancy, thus determining the reaction order. As RH increases, water starts to condense on the surface and the gas-liquid reaction of NO2 with the condensed water begins. With high enough RH 52% in our experiment), the gas-liquid reaction of NO2 with condensed water becomes dominant, forming HNO3 and HONO. The initial uptake coefficient gamma(0) was determined to be (4.25 1.18)x10(-9) under dry conditions and up to (6.56 0.34)x10(-8) under wet conditions. These results suggest that the reaction of NO2 on CaCO3 particle is unable to compete with that of HNO3 in the atmosphere. Further studies at lower NO2 concentrations and with a more accurate assessment of the surface area for calculating the uptake coefficient of the reaction of NO2 on CaCO3 particle and to examine its importance as a source of HONO in the atmosphere are needed.

Cite this document (BETA)

Readership Statistics

11 Readers on Mendeley
by Discipline
 
 
 
by Academic Status
 
27% Post Doc
 
27% Ph.D. Student
 
18% Student (Bachelor)
by Country
 
9% United States

Sign up today - FREE

Mendeley saves you time finding and organizing research. Learn more

  • All your research in one place
  • Add and import papers easily
  • Access it anywhere, anytime

Start using Mendeley in seconds!

Already have an account? Sign in