Investigation of the absorption Ångström exponent and its relation to physicochemical properties for mini-CAST soot. Issue 7 (3rd July 2018)

• Record Type: Journal Article
• Authors: Török, Sandra; Malmborg, Vilhelm B.; Simonsson, Johan; Eriksson, Axel; Martinsson, Johan; Mannazhi, Manu; Pagels, Joakim; Bengtsson, Per-Erik
• Is Part Of: Aerosol science and technology. Volume 52:Issue 7(2018)
• Page Start: 757
• Page End: 767
• Publication Date: 2018-07-03
• Subjects: Matti Maricq; Aerosols -- Periodicals; Aerosol Propellants -- Periodicals; Aerosols -- Periodicals; 660.294515
• DOI: 10.1080/02786826.2018.1457767
• Languages: English
• ISSNs: 0278-6826

Abstract

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, AAE s 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 AAE s 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. Copyright © 2018 The Authors