PERSONAL DE APOYO
NAJERA juan jose
artículos
Título:
Infrared spectroscopic studies of the heterogeneous reaction of ozone with dry maleic and fumaric acid aerosol particles
Autor/es:
J.J. NAJERA; C.J. PERCIVAL; A.B. HORN
Revista:
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Editorial:
ROYAL SOC CHEMISTRY
Referencias:
Lugar: CAMBRIDGE; Año: 2009 vol. 11 p. 9093 - 9103
ISSN:
1463-9076
Resumen:
Dicarboxylic acids, either directly emitted or formed in chemical processes, are found to be a
significant component of tropospheric aerosols. To assess any potential chemical transformation
of short unsaturated dicarboxylic acids in tropospheric heterogeneous chemistry, maleic and
fumaric acid were selected as surrogates in this study. A novel aerosol flow tube apparatus is
employed to perform kinetic studies of the oxidation of these organic compounds by gas-phase
ozone. The system consists of a particle generation system, a vertically oriented glass flow tube
and an infrared observation White cell with a Fourier transform infrared (FTIR) spectrometer for
the detection system. A flow of single component organic aerosols with mean diameters ranging
between 0.7 and 1.1 mm is introduced in a flow tube, in which the particles are subsequently
exposed to a known concentration of ozone for a controlled period of time. A band assignment
of infrared vibrational frequencies for dry maleic and fumaric acid aerosol spectra is presented.
These studies are complemented with off-line analysis on the reaction products. The reaction
exhibited pseudo-first-order kinetics on gas product formation, and the pseudo-first-order rate
coefficients displayed a Langmuir?Hinshelwood dependence on gas-phase ozone concentration for
both materials. By assuming a Langmuir?Hinshelwood behaviour, the following parameters were
obtained: for the reaction of maleic acid aerosols, KO3
= (3.3 + 0.5) 1016 cm3 molecule1
and kI
max = (0.038 + 0.004) s1; for the reaction of fumaric acid aerosols, KO3
= (1.6 + 0.5)
1016 cm3 molecule1 and kI
max = (0.048 + 0.007) s1, where KO3
is a parameter that describes
the partitioning of ozone to the particle surface and kI
max is the maximum pseudo-first-order
coefficient at high ozone concentrations. Apparent reactive uptake coefficients were estimated
from the pseudo-first-order rate coefficient and a trend of decreasing uptake coefficients with
increasing ozone concentrations was observed, in good agreement with literature values.