Sulphur dioxide (SO2)

Sulphur dioxide (SO2) is a dense colourless gas, which is soluble in water, and has a suffocating and unpleasant smell like burnt matches.

Sulphur dioxide gas can be made directly by heating Sulphur in air. The most common source of this is the burning of coal for electricity generation.

The gas is considered harmful to human health, it places stress on the cardio-vascular and respiratory systems, with increasing evidence that it can trigger asthma in certain individuals.

Sulphur dioxide is also the major component of acid rain since it mixes with water vapour in the atmosphere, reacting to produce sulphuric acid (H2SO4). This is possible as UV radiation in the upper atmosphere catalyses the reaction between sulphur dioxide and oxygen to produce sulphur trioxide which goes on to react with water to form a weak dibasic sulphuric acid.

This is harmful to flora and fauna and in particular aquatic ecosystems. Sulphuric acid can directly kill all but the most tolerant species e.g. eels and through its ability to mobilise compounds it can have a devestating impact on freshwater biology.

In Shrewsbury and Atcham Borough the only major source of SO2 is the power station in Ironbridge.  The site is regulated by the Environment Agency to ensure that the SO2 it emits does not reach harmful levels.

Recent tightening of this regualtion has resulted in significant improvements in air quality for this pollutant, on this basis of this it is not currently necessary to declare any AQMA's for SO2 in the area.

A detailed report into levels of SO2 from Ironbridge Power Station has been prepared jointly by Bridgnorth District Council, Shrewsbury and Atcham Borough Council and Telford and Wrekin Unitary Authority.

This can be downloaded below

(word format, 4.8mb)