A novel multii-wavelength photoacoustic spectrometer for the measurement of the UV-vis-NIR spectral absorption coefficient of atmospheric aerosols

Tibor Ajtai, Ágnes Filep, Martin Schnaiter, Claudia Linke, Marlen Vragel, Zolt Án Bozóki, GÁbor Szabó, Thomas Leisner

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

A multi-wavelength photoacoustic instrument is described, which measures the wavelength dependent optical absorption coefficient (OAC) of soot or soot-containing aerosols in-situ in a range from the ultra-violet to the near-infrared region. The instrument combines a Nd:YAG disc laser (fundamental wavelength 1064nm, harmonics at 532, 355 and 266nm) and four photoacoustic detection cells, each purged with the same aerosol sample flow, while being irradiated with one of the four light beams. With the help of a supplementary optical arrangement to illuminate each detection cell with 532nm light, the system is calibrated against OAC by purging the cells with known concentrations (and hereby known OAC values) of NO2. This calibration eliminates differences in sensitivity of the detection PA cells and makes the measurement of OAC absolute. The minimum detectable OAC was determined to be 0.2Mm-1 at 1064nm and 35.5Mm-1 at 266nm, corresponding to a minimum detectable black carbon mass concentration of about 0.1-1μg/m3, depending on the wavelength. Comparison measurements with artificially generated soot aerosols showed good agreement of the device with a reference instrument, based on a long path extinction cell (LOPES).

Original languageEnglish
Pages (from-to)1020-1029
Number of pages10
JournalJournal of Aerosol Science
Volume41
Issue number11
DOIs
Publication statusPublished - Nov 2010

Keywords

  • Absorption coefficient
  • Black carbon
  • Multi-wavelength
  • Photoacoustic
  • ÅngstrÖm exponent

ASJC Scopus subject areas

  • Environmental Engineering
  • Pollution
  • Mechanical Engineering
  • Fluid Flow and Transfer Processes
  • Atmospheric Science

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