Acousto-optic differential optical absorption spectroscopy for atmospheric measurement of nitrogen dioxide in Hong Kong

Andrew Y.S. Cheng*, Mau Hing CHAN

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

Measurement of the atmospheric concentration of nitrogen dioxide (NO 2) pollutant was demonstrated by differential optical absorption spectroscopy (DOAS) using a visible acousto-optic tunable filter. In a traditional spectral scanning DOAS system for atmospheric concentration monitoring, a highly stable light source is required. When the light intensity fluctuates during scanning, the concentration retrieval will be inaccurate. In order to reduce the error due to intensity fluctuations, a modified DOAS system has been developed by introducing a broadband light intensity monitoring channel. Using the measured intensity of the broadband channel as the intensity of the light source, the spectrum can be de-biased and the residual intensity variation will primarily result from atmospheric extinction. In addition, by employing the lock-in detection technique, the background light interference is also removed in the modified DOAS system. The atmospheric NO2 concentration measurement was performed at the campus of City University of Hong Kong, and the results were compared with the concentration reported from a nearby monitoring station in Sham Shui Po, operated by the Hong Kong Environmental Protection Department.

Original languageEnglish
Pages (from-to)1462-1468
Number of pages7
JournalApplied Spectroscopy
Volume58
Issue number12
DOIs
Publication statusPublished - Dec 2004

Scopus Subject Areas

  • Instrumentation
  • Spectroscopy

User-Defined Keywords

  • Acousto-optic tunable
  • Atmospheric pollutant monitoring
  • Differential absorption spectroscopy
  • Visible spectroscopy

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