Episodes
Figure 1: Air pollution episodes can often be a problem in cities such as Middlesbrough [Picture from 1].
Summa Walker
EERE UG 4: Air and Water Pollution Modelling
UK Air Pollution Episodes
An air pollution episode is the term used for a period of poor air quality, lasting up to several days, often extending over a large geographical area [2]. Concentrations of all the measured species may increase at the same time, or only one species may be affected. 'Air Pollution Bands' classify pollution levels into bands to enable air quality levels to be identified, see table 1.
Description...
Low
S
Moderate
I
High
A
Very High
Sulphur Dioxide (ppb, 15 minute averages)
<100
00-199
200-399
>=400
Ozone (ppb)
<50 (8hr running average)
50-89 (hourly average)
90-179 (hourly average)
>=180 (hourly average)
Carbon Monoxide (ppm, 8 hour running average)
<10
0-14
5-19
>=20
Nitrogen Dioxide (ppb, hourly average)
<150
50-299
300-399
>=400
PM10 Particles (µg/m3, 24 hour running average)
<50
50-74
75-99
>=100
S = Standard Threshold, I = Information Threshold, A = Alert Threshold
Table 1: Air Pollution bands for some major pollutants [from 5]
There are different types of episode, caused in different ways:
* Winter episodes occur during periods of cold calm weather when pollution emissions are trapped close to their sources and cannot disperse.
* Summer episodes are characterised by high ozone levels and occur during warm sunny weather in the summer months.
* Non seasonal episodes, for example particulate pollution episodes due to transport of particulate matter from industrial areas of central Europe, plume grounding episodes where specific weather conditions push emissions from large industrial chimney stacks down to ground level and episodes caused by release of a concentrated source (spill).
Winter Episodes
During cold calm periods of weather in the winter months, pollution emissions are trapped close to their sources and cannot disperse leading to a build up of pollution. This commonly happens due to an inversion layer in the atmosphere and, as a result, elevated concentrations of a range of pollutants can build up over several days. The biggest source of air pollution currently in most UK cities is road traffic and high concentrations of nitrogen oxides, particulates and hydrocarbons are usually observed during mid-winter episodes
Figure 1: Air pollution episodes can often be a problem in cities such as Middlesbrough [Picture from 1].
Summa Walker
EERE UG 4: Air and Water Pollution Modelling
UK Air Pollution Episodes
An air pollution episode is the term used for a period of poor air quality, lasting up to several days, often extending over a large geographical area [2]. Concentrations of all the measured species may increase at the same time, or only one species may be affected. 'Air Pollution Bands' classify pollution levels into bands to enable air quality levels to be identified, see table 1.
Description...
Low
S
Moderate
I
High
A
Very High
Sulphur Dioxide (ppb, 15 minute averages)
<100
00-199
200-399
>=400
Ozone (ppb)
<50 (8hr running average)
50-89 (hourly average)
90-179 (hourly average)
>=180 (hourly average)
Carbon Monoxide (ppm, 8 hour running average)
<10
0-14
5-19
>=20
Nitrogen Dioxide (ppb, hourly average)
<150
50-299
300-399
>=400
PM10 Particles (µg/m3, 24 hour running average)
<50
50-74
75-99
>=100
S = Standard Threshold, I = Information Threshold, A = Alert Threshold
Table 1: Air Pollution bands for some major pollutants [from 5]
There are different types of episode, caused in different ways:
* Winter episodes occur during periods of cold calm weather when pollution emissions are trapped close to their sources and cannot disperse.
* Summer episodes are characterised by high ozone levels and occur during warm sunny weather in the summer months.
* Non seasonal episodes, for example particulate pollution episodes due to transport of particulate matter from industrial areas of central Europe, plume grounding episodes where specific weather conditions push emissions from large industrial chimney stacks down to ground level and episodes caused by release of a concentrated source (spill).
Winter Episodes
During cold calm periods of weather in the winter months, pollution emissions are trapped close to their sources and cannot disperse leading to a build up of pollution. This commonly happens due to an inversion layer in the atmosphere and, as a result, elevated concentrations of a range of pollutants can build up over several days. The biggest source of air pollution currently in most UK cities is road traffic and high concentrations of nitrogen oxides, particulates and hydrocarbons are usually observed during mid-winter episodes