Use of nitrogen dioxide (NO2) passive diffusion tubes
Wiltshire Council currently has approximately 100 sites around the county to monitor for nitrogen dioxide.
Passive diffusion tubes are not as accurate as real time monitoring due to the long averaging time employed by this method. The results cannot show directly whether an exceedence has occurred but can identify areas where the reference monitoring methods need to be adopted.
A nitrogen dioxide passive diffusion tube is a clear plastic tube open at one end and at the closed end a mesh is impregnated with a pollutant absorbing chemical. The diffusion tube collects the pollutant during the exposure period and then is resealed and returned to a laboratory for analysis. Each tube is exposed for a month period. The laboratory then assesses the quantity of the pollutant absorbed by calculating the average ambient NO2 concentration over the exposure period.
Each tube is mounted on a lamp-post or similar structure ensuring that the open end is at the bottom to prevent rainwater collection.
Wiltshire Council utilises diffusion tubes prepared and analysed by Bristol City Scientific Services. The laboratory participate in the Workplace Analysis Scheme for Proficiency (WASP) for nitrogen dioxide tubes.
They analyse a solution supplied by Netcen as part of the QA/QC scheme that they run.
The laboratory also participate in a field inter-comparison scheme which is controlled by Netcen and organised by the Health and Safety Laboratory. Three tubes are co-located with a continuous analyser which provides a reference value.
The tubes are prepared by pipetting 30l of solution of 20% triethanolamine in water onto the metal grids in the end of the cap, then assembling the tube components. A fresh batch of tubes is prepared each month ready to dispatch in time for the required exposure date.
Laboratory blanks are retained so that at least one is run alongside each batch of samples. Travel blanks are supplied three-monthly as required by the UK survey procedure.
Contact Details (LiveLink)
Multiple Contacts:
Please contact the Specialist Pollution team in the area to which your contaminated land, air quality or environmental permit enquiry relates:
North Wiltshire:
Specialist
Pollution Team
Wiltshire
Council
Monkton Park
Chippenham
Wiltshire
SN15
1ER
Telephone: 01249 706555
Email:
publicprotectionnorth@wiltshire.gov.uk
(This office deals with all applications relating to Chippenham, Calne, Corsham, Malmesbury and Wootton Bassett as well as the rest of the old North Wiltshire District Council area).
East Wiltshire:
Public
Protection
Wiltshire Council
Browfort
Bath Road
Devizes
Wiltshire
SN10
2AT
Telephone: 01380 734721
Email:
publicprotectioneast@wiltshire.gov.uk
(This office deals with all applications relating to Devizes, Pewsey, Marlborough and Tidworth as well as the rest of the old Kennet District Council area).
South Wiltshire:
Public
Protection
Wiltshire Council
27/29 Milford Street
Salisbury
SP1
2AP
Telephone: 01722 434340
Email:
publicprotectionsouth@wiltshire.gov.uk
(This office deals with all applications relating to Salisbury, Amesbury, Downton, Mere, Hindon and Tishead as well as the rest of the old Salisbury District Council area).
West Wiltshire:
Public
Protection
Wiltshire Council
Bradley Road
Trowbridge
Wiltshire
BA14
0RD
Telephone: 01225 776655
Email:
publicprotectionwest@wiltshire.gov.uk
(This office deals with Trowbridge, Bradford-on-Avon, Melksham, Warminster and Westbury as well as the rest of the old West Wiltshire District Council area).
If you are unsure which is the correct area please contact 0300 456 0100 or email EPSpecialist@wiltshire.gov.uk
eMail:
Telephone:
Out of hours:
Fax:
Postal Address:
In Person:
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Last updated: 1 September 2010
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