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.
- Analyzing method: UV-fluorescence.
- 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.
- Sulfate by ion chromatography
- Total sulfur with PIXE. See Elements