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Sulfur dioxide (SO2) and particulate sulfur

The results are used for smog warning.

Measurement method (half hour measurements)

Sulfur dioxide (SO2) is measured by ultraviolet fluorescence. The air is drawn into a chamber which is illuminated with ultraviolet light. The SO2 molecules are estimated by the ultraviolet light and when they return to the normal state, light is emitted with a longer wavelength. By recording this light in a photosensor, one can determine the concentration of SO2.

Technical description

  • Analyzing method: UV-fluorescence.
    SO2 monitors:
  • Principle: Fluorescence measurements by UV radiation.
  • Measuring range: 0-500 ppb, at 0.6-0.8 l/min.
  • Lower detection limit: <1 ppb
  • Precision ±5%
  • Selectivity: NO gives a positive interference of approx. 2%.
  • Routine checks: Automatic zero point check every day around midnight with zero- air from a generator. Automatic span check once a week with around 200 ppb SO2 in syntetic air from a pressure bottle.
  • Calibration at the laboratory: 1) Diluted reference gas (from Messer Griesheim) of 12 ppm of SO2in syntetic air. 2) Diluted SO2 gas from a permeation tube. 

24 hour measurements SO2:

Collected on KOH-impregnated filters and analyzed by ion chromatography.

Particular sulfur:

Analyzed as:

  • Sulfate by ion chromatography
  • Total sulfur with PIXE. See Elements