SO2 concentration in the Netherlands (annual and winter averages), 1992-2002
In 2000, the average annual concentration of sulphur dioxide (SO2) did not exceed the limit value anywhere in the Netherlands. Concentrations in the south-west of the Netherlands are higher than in the rest of the country due to the proximity of large sources in the Rijnmond area.
Sulphur dioxide concentration continues to fall
The annual average SO2 concentration continued to fall in 2002. The limit value for the SO2 concentration for the protection of ecosystems (20 µg/m3) was not exceeded anywhere in the Netherlands in 2002.
The annual average SO2 concentration fell in the last ten years by approximately 7% a year. This is the result of emission reductions in the Netherlands and abroad from the main sources of SO2, such as electricity plants, refineries and traffic. Because the first two sources generate most emissions by far, urban concentrations are higher than street concentrations.
The concentrations in the winter have increased slightly because of a number of processes associated with the lower temperatures: increased amounts from elsewhere due to continental winds, higher emissions as a result of space heating, less favourable atmospheric distribution and a lower deposition of sulphur dioxide when there is snow on the ground.
Highest concentrations in south-west of the Netherlands
The highest levels were observed in the Rijnmond area, Zeeland and in the south-west of North Brabant. They are linked to local industry and shipping and possibly also the proximity of sources in West Flanders.
European standards for exposure to sulphur dioxide
The EU has adopted a number of limit values for SO2 concentrations for the protection of public health and ecosystems (EU, 1999).
- To protect ecosystems against the impact of prolonged exposure, a limit value has been set of 20 µg/m3. This applies to both the average for the calendar year and to the winter half of the year (see figures above).
- The EU has adopted two limit values to protect humans against peak concentrations of SO2. The 24-hour average SO2 concentration must not exceed the limit of 125 ug/m3 more than 3 times a year; the hourly average concentration must not exceed 350 ug/m3.
Sources of sulphur dioxide
Emissions of SO2 to air usually occur as a result of the use of sulphurous motor fuels. The main sources are electricity plants, refineries and traffic.
Impact of sulphur dioxide on people and nature
High concentrations of SO2 have a negative impact on humans, animals and plants. For example, SO2 contributes to the acidification of ecosystems.
