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Investigation of the absorption Ångström exponent and its relation to physicochemical properties for mini-CAST soot

Török, Sandra LU ; Malmborg, Vilhelm B. LU ; Simonsson, Johan LU ; Eriksson, Axel LU ; Martinsson, Johan LU ; Mannazhi, Manu LU ; Pagels, Joakim LU and Bengtsson, Per Erik LU (2018) In Aerosol Science and Technology 52(7). p.757-767
Abstract

In this work, a mini-CAST soot generator was used to produce soot with different optical and physicochemical characteristics. Absorption Ångström exponents (AAE) expressing the absorption wavelength dependence were assessed by multiwavelength in-situ and filter-based (aethalometer) laser extinction. The two optical techniques showed good agreement. For the chosen mini-CAST operating conditions, AAEs between 1 and 3.5 were found. Soot with high mass-fractions of organic carbon (OC) and pyrolytic carbon (PC) determined with thermal optical analysis were associated with AAEs significantly higher than 1. Heating to 250 and 500°C removed the majority of polycyclic aromatic hydrocarbons. However, the thermal-optical analysis revealed that OC... (More)

In this work, a mini-CAST soot generator was used to produce soot with different optical and physicochemical characteristics. Absorption Ångström exponents (AAE) expressing the absorption wavelength dependence were assessed by multiwavelength in-situ and filter-based (aethalometer) laser extinction. The two optical techniques showed good agreement. For the chosen mini-CAST operating conditions, AAEs between 1 and 3.5 were found. Soot with high mass-fractions of organic carbon (OC) and pyrolytic carbon (PC) determined with thermal optical analysis were associated with AAEs significantly higher than 1. Heating to 250 and 500°C removed the majority of polycyclic aromatic hydrocarbons. However, the thermal-optical analysis revealed that OC and PC were abundant in the soot with AAE > 2 also after heating the aerosol. Analysis of mass absorption cross section ratios for elemental carbon and OC indicated that elevated AAEs also after heating to 500°C could be related to persistent OC and PC components and/or the refractory soot. By comparing the mini-CAST soot optical properties with soot properties derived from in-situ extinction measurements in a premixed flame, mini-CAST soot with a higher AAE could be identified as less mature soot.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Aerosol Science and Technology
volume
52
issue
7
pages
757 - 767
publisher
Taylor & Francis
external identifiers
  • scopus:85045834020
ISSN
0278-6826
DOI
10.1080/02786826.2018.1457767
language
English
LU publication?
yes
id
d53b849c-713c-48fd-8bae-02cc9db4329e
date added to LUP
2018-05-04 10:00:33
date last changed
2019-01-14 17:02:55
@article{d53b849c-713c-48fd-8bae-02cc9db4329e,
  abstract     = {<p>In this work, a mini-CAST soot generator was used to produce soot with different optical and physicochemical characteristics. Absorption Ångström exponents (AAE) expressing the absorption wavelength dependence were assessed by multiwavelength in-situ and filter-based (aethalometer) laser extinction. The two optical techniques showed good agreement. For the chosen mini-CAST operating conditions, AAEs between 1 and 3.5 were found. Soot with high mass-fractions of organic carbon (OC) and pyrolytic carbon (PC) determined with thermal optical analysis were associated with AAEs significantly higher than 1. Heating to 250 and 500°C removed the majority of polycyclic aromatic hydrocarbons. However, the thermal-optical analysis revealed that OC and PC were abundant in the soot with AAE &gt; 2 also after heating the aerosol. Analysis of mass absorption cross section ratios for elemental carbon and OC indicated that elevated AAEs also after heating to 500°C could be related to persistent OC and PC components and/or the refractory soot. By comparing the mini-CAST soot optical properties with soot properties derived from in-situ extinction measurements in a premixed flame, mini-CAST soot with a higher AAE could be identified as less mature soot.</p>},
  author       = {Török, Sandra and Malmborg, Vilhelm B. and Simonsson, Johan and Eriksson, Axel and Martinsson, Johan and Mannazhi, Manu and Pagels, Joakim and Bengtsson, Per Erik},
  issn         = {0278-6826},
  language     = {eng},
  month        = {04},
  number       = {7},
  pages        = {757--767},
  publisher    = {Taylor & Francis},
  series       = {Aerosol Science and Technology},
  title        = {Investigation of the absorption Ångström exponent and its relation to physicochemical properties for mini-CAST soot},
  url          = {http://dx.doi.org/10.1080/02786826.2018.1457767},
  volume       = {52},
  year         = {2018},
}