Other data sources for air pollution
In addition to APIS, the table below provides information on a number of other sources of data on air pollution. These mainly include monitoring data provided by the UK National Air Quality Information Archive and local authorities. The majority of these other data sources are designed for Local Air Quality Management. The table below summarises these sources and makes a comparison to the data provided in the APIS simple site-based assessment tool. A few pointers to remember are:
- monitoring data can be useful when assessing a specific site, but only where a monitoring station or a close set of monitoring stations is/are situated.
- most air quality monitoring is targeted at measuring exposure to humans and assessing levels against national air quality objectives. Hence, the majority of monitoring stations are set up to measure concentrations around areas where people are exposed to high concentrations, such as close to emissions sources in urban areas and adjacent to busy roads. There are, however, urban background monitoring sites that measure away from potential emission sources and rural sites (full site classification). They do not, as in APIS, generally give a good estimate of air quality at nature conservation sites or other semi-natural areas which are often (but not always) situated in rural locations (except where a rural monitoring site is situated).
| Source | Description | Data | Comments and comparisons with APIS data |
UK National Air Quality Information Archive (www.airquality.co.uk). This site was developed by NETCEN, part of AEA Technology Environment, on behalf of the Department for Environment, Food & Rural Affairs (DEFRA) and the Devolved Administrations. Some data goes back as far as 1960. |
There are over 1500 sites across the UK which monitor air quality. They are organised into networks that gather a particular kind of information, using a particular method. Non-Automatic Networks 1. NO2 Diffusion Tube Network 2. Lead and multi-element monitoring network 3. Smoke and Sulphur Dioxide Monitoring Network 4. Toxic Organic Micro Pollutants 5. Acid Deposition Monitoring Network (see below) 6. Rural Sulphur Dioxide Monitoring Network Automatic Networks 1. the Automatic Urban Network (AUN) 2. the Automatic Rural Network (ARN) 3. the Hydrocarbon Network |
The networks provide measured hourly, daily and annual pollutant concentrations, and statistics, including air pollutant concentrations for individual sites, maps of pollutant emissions and acid depositions data. | The majority of the 1500 sites are in urban areas and are used for monitoring air quality predominantly to protect human health. However, they provide valuable measurements used in calculating pollutant maps for the UK and in calibrating modelled outputs. In APIS, data from the networks are used in calculating UK maps for acid and nitrogen deposition, NO2, SO2 and Ozone (O3). |
Local Background Monitoring |
Maps of estimated background annual mean air pollutant concentrations at a 1 km x 1 km grid resolution are available for the year 2001: NOx, NO2, PM10, PM10 secondary, SO2, Benzene, CO and 1,3-butadiene. The following maps of projected concentrations are also available: NOx (2005, 2010), NO2 (2005, 2010), PM10 (2004, 2010), Benzene (2003, 2010), and 1,3-butadiene (2003). |
Maps for NOx are made up of a combination of interpolated rural measured concentrations (from the Acid Deposition Monitoring Network), area source modelled values calibrated to the national measured concentrations, and contributions from major points sources using ADMS modelling. An additional roadside contribution is added to account for locations close to road traffic sources. |
The method for calculating the NOx map is the same as that in APIS.
However, estimates on the Air Quality Archive are presented at a higher resolution than in APIS (1x1km grid square compared to 5x5km respectively).
Slightly different methods are used in calculating the SO2 map. While the LAQM method uses dispersion modelling APIS uses an interpolated rural SO2 map with additional urban SO2 derived by a regression procedure. CEH believe that the method used in APIS gives
a better representation for the purposes of assessment of protected nature
conservation sites, however, this is an area of scientific debate. Further improvements in the dispersion modelling, and particular local modelling near point sources, will provide a better estimate in the future. Like the NOx estimates, the data in Air Quality Archive is at a resolution of 1x1km compared to a 5x5km resolution in APIS. |
| Local Authorities (search for your local authority web site) The Environment Act 1995, providing a system for Local Air Quality Management (LAQM), requires all local authorities to periodically review and assess air quality in their areas and predict the future air quality and compared against air quality objectives. Councils often act as local site operators for sites run by NETCEN (see above), in addition to their own monitoring sites. Ssome local authorities publish data via their regional networks e.g. Welsh Air Quality Forum |
Under LAQM a local authority must assess the following pollutants: 1,3 – butadiene, Sulphur dioxide Benzene, Lead, Carbon monoxide, Particles PM10 and Nitrogen dioxide. | Passive diffusion tubes, over 1100 urban sites, are used to monitor monthly averages of nitrogen dioxide (NO2 Diffusion Tube Network). Each authority places samplers at two kerbside locations (1 to 5 m from a major road) and two urban background sites (in residential areas more than 50m from a major road). Real time analysers are also used at sites that continually monitor concentrations as often as 15 minute and hourly time intervals. There are currently around 165 sites in the Smoke and Sulphur Dioxide Monitoring Network which monitor black smoke and SO2 on a daily basis. | The monitoring sites are used primarily to monitor air quality to protect human health and assist with the implementation of LAQM. However, since they are part of the overall UK National Air Quality Information Archive networks they also provide valuable measurements used in calculating pollutant maps for the UK. |
| UK National Ammonia Monitoring Network (www.cara.ceh.ac.uk). Following concern about the possible environmental impacts of atmospheric ammonia (NH3), the Department for Environment, Food & Rural Affairs (DEFRA) is supporting work to monitor the air concentrations of ammonia and ammonium across the UK. The network is managed by The Centre for Ecology and Hydrology |
For the ammonia network a two tiered approach is being used. A baseline network of around 50 sites samples using active denuders (where power is available), while a secondary network of passive diffusion tubes explores air concentration variability in high concentration areas, with the method calibrated at 10 sites against the denuder approach. | For all sites sampling is on a monthly basis. This allows seasonal patterns to be investigated, while allowing sufficient resources for long term trends and spatial patterns to be assessed. Ammonia (NH3) and Ammonium (NH4+ ) are both measured. The network website also provides concentration maps and interpolated maps for the UK. | The measured data from the ammonia network are used to provide the ammonia concentration maps for the UK in APIS. The network measurements are used to calibrate the NH3 concentration estimates of the FRAME atmospheric dispersion model, which spatially estimates NH3 emissions at a 5 km grid resolution. These maps are subsequently used in the calculation for maps of acid and nitrogen deposition. |
| Acid Deposition Monitoring in the UK (Acid Deposition Monitoring Network) These pages contain information about the acid deposition monitoring networks managed by the NETCEN on behalf of DEFRA. The network is part of the overall UK National Air Quality Information Archive. |
Acid deposition is currently measured at 38 weekly sites across the UK. Wet deposition is calculated from the concentration of the specified ion in precipitation and the Meteorological Office rainfall field. As part of the Acid deposition monitoring, rural NO2 and SO2 are also measured at approximately 32 sites across the UK and the interpolated concentration field is combined with a process-based model (ITE) to estimate the dry deposition of sulphur to the UK. | Since 1989 the network has comprised:
The 'Primary Network': Five sites at which precipitation composition ( acidity, sulphate, nitrate, ammonium, sodium, chloride, magnesium, calcium, potassium, phosphate and conductivity) was measured. Samples were collected using wet-only collectors.
The 'Secondary Network': Thirty two sites (including the Primary sites) at which the same precipitation composition parameters were measured on weekly samples collected using bulk collectors. For the NO2 and SO2 rural sites measurements are taken on a weekly basis for SO2 and fortnightly or monthly for NO2. |
Data from both networks are used to calculate concentration and wet deposition (enhanced) maps for the UK. These are used in combination with estimates of dry deposition and cloud deposition to provide estimates of total deposition which are compared with critical loads. |