Time Resolved Infrared Spectroscopy of Formation and Processing of Secondary Organic Aerosol
An aerosol flow reactor was coupled to an infrared absorption cell to study aerosol formation processes with high temporal resolution. The recorded infrared spectra were referenced using aerosol smog chamber experiments. Evaluation was done by studying the formation of secondary organic aerosol from...
Saved in:
Published in | Zeitschrift für physikalische Chemie (Neue Folge) Vol. 224; no. 7; pp. 1171 - 1183 |
---|---|
Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
De Gruyter Oldenbourg
01.08.2010
|
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | An aerosol flow reactor was coupled to an infrared absorption cell to study aerosol formation processes with high temporal resolution. The recorded infrared spectra were referenced using aerosol smog chamber experiments. Evaluation was done by studying the formation of secondary organic aerosol from α-pinene and catechol as precursors and ozone as oxidant. Three main infrared absorptions: ν(O-H), ν(C-H) and ν(C=O) were considered, and humic like properties of the secondary organic aerosol are mainly interpreted according to the formation and variations of carbonyl bands in the region between 1850 and 1600 cm
, especially the ν(C=O) of aryl carbonyls from catechol oxidation products below 1700 cm
. The relative intensities of two major ν(C=O) stretching vibrations at 1690 cm
and 1755 cm
were observed to depend strongly on the available ozone concentration. At high precursor/ozone ratios (2:1 or 1:1) the vibration at 1690 cm
predominates, indicating aryl carbonyl vibrations. With increasing ozone concentrations this vibration is replaced by the higher carbonyl vibration at 1755 cm
indicating unsaturated carbonyl-containing compounds. This is a strong hint at ring opening processes leading to unsaturated aliphatic compounds in the resulting particle. Aryl carbonyls and aromatic or olefinic ν(C=C) at 1620 cm
in aged particles remain visible, as aerosol smog chamber studies exhibit – thus a strong hint at humic like properties of the SOA from the spectroscopic point of view. |
---|---|
ISSN: | 0942-9352 2196-7156 |
DOI: | 10.1524/zpch.2010.6146 |