The Concentration Based Estimated Deposition (CBED) methodology (e.g. RoTaP, 2012) produces 1x1 gridded data of deposition of sulphur, oxidised and reduced nitrogen, ammonia concentration and base cations at 1 km x 1 km resolution, using measured concentrations of gases and particulate matter in air and ions in precipitation, together with a modelled spatial pattern of ammonia concentrations. Measured data are collected at sites in the UK Eutrophying and Acidifying Pollutants (UKEAP) network (Braban et al., 2021; Conolly et al., 2018). The ion concentrations in precipitation are combined with an annual precipitation map from the UK Meteorological Office, at 5 km x 5 km resolution, to generate values for wet deposition rates. Gridded data of gas and particulate matter concentrations are combined with spatially distributed estimates of habitat-specific deposition velocities (Smith et al., 2000) to generate dry deposition for five land cover categories: forest, moorland, fertilised grassland, arable and urban. For each grid cell, the mean deposition weighted by the areas of these land cover is calculated, termed the Grid Average deposition. Dry deposition includes deposition of gases sulphur dioxide (SO2), nitric acid (HNO3), nitrogen dioxide (NO2) and ammonia (NH3) and particulate matter (sulphate, nitrate, ammonium, calcium and magnesium) onto vegetation. Wet deposition includes deposition from precipitation as well as direct deposition of cloud droplets to vegetation (known as ‘occult’ deposition) and is mapped for sulphate, ammonium, nitrate, calcium, magnesium, and acidity (hydrogen ion). The 5 x 5 km grid resolution estimates are downscaled to 1 x 1 km grid resolution using bilinear interpolation. For critical load exceedance calculations, deposition values for ‘moorland’/short vegetation are applied to all non-woodland sensitive habitats (e.g. bogs, heaths, semi-natural grasslands), and deposition values for the forest land cover type are applied to all woodland habitats. The grid-average deposition is not appropriate for assessing habitat-specific deposition rates, but is useful for assessing total deposition load, for example to a catchment.
Data Inputs, Modelling and Calibrations
Nitric acid concentrations are calculated by interpolation of measurements from about 30 sites. NO2 and SO2 concentrations are taken from the Pollution Concentration Mapping (PCM) model (Stedman et al., 2007). This latter data set includes a combination of interpolation of measurements from rural sites combined with modelling concentrations from point sources and line sources e.g. roads.
Ammonia concentrations at 3 km x 3 km horizontal resolution are taken from EMEP4UK (Vieno et al., 2016), a UK application of the the European Monitoring and Evaluation Programme (EMEP) MSC-W atmospheric chemistry transport model version rv4.45 (EMEP MSC-W - https://github.com/metno/emep-ctm). Emissions of NH3 for the UK are derived from the National Atmospheric Emission Inventory estimate at grid resolution of 1km x 1km grid resolution (NAEI, http://naei.defra.gov.uk). For all non-UK emissions, the EMEP emission estimates are used at a resolution of 0.1° × 0.1° provided by the Centre for Emission Inventories and Projections (CEIP, http://www.ceip.at/).
The EMEP4UK outputs for each year are based on emissions and meteorology data for that year, with the exception of the most recent year. The most recent year uses that year’s meteorology data, together with emissions data from the previous year, since there is an inevitable delay in collating and updating the emissions data. Emissions change relatively little from year to year and the spatial pattern of pollution is mainly driven by meteorological conditions, so this procedure is not thought to greatly affect the accuracy of CBED outputs.
The Weather Research Forecast (WRF) version 4.4.2 model was used as the main meteorological driver of EMEP4UK (www.wrf-model.org). The WRF model (Skamarock et al., 2019) included data assimilation (Newtonian nudging) of the numerical weather prediction (NWP) model meteorological reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-5 reanalysis at 0.25° x 0.25° degrees resolution, every 6 hours (Hersbach et al., 2020).
Process modelling has associated uncertainties, so EMEP4UK outputs of ammonia concentrations are calibrated using linear regression to measured concentrations from the UKEAP National Ammonia Monitoring Network atom-feed (https://uk-air.defra.gov.uk/data/atom-dls/), using a proportional relationship to scale the modelled concentrations according to the measurements. Data from all ammonia monitoring stations that had a temporal coverage of measurements data for at least 70% of the year were used for calibration, with the exception of a few stations where the measurements were known not to be representative of the surrounding area as modelled for the grid cell, e.g. because of the proximity to individual sources. Individual years were also removed from the calibration dataset where the annual mean deviated substantially from the long-term mean for the site.
Mapping wet deposition includes an orographic enhancement factor for the concentration of precipitation in upland regions due to the seeder-feeder effect. The enhancement factor is taken from observations of the increase in ion concentrations with altitude observed at Great Dun Fell in the Northern Pennines (Fowler et al., 1988) and subsequently confirmed by measurements at Holme Moss in the southern Pennines (Dore et al., 2001 ; Beswick et al., 2003).
Significant inter-annual variations in deposition can occur due to the natural variability in annual weather patterns including precipitation, which directly influences wet deposition. The circulation of the air, temperature and precipitation also affect emissions, atmospheric chemistry and transport. Therefore, the CBED deposition data used to calculate the exceedance of critical loads are averaged over a three year period. This has been demonstrated to be a suitable time period to smooth out some of the inter-annual variations in deposition.
Data are calculated on an annual basis but provided as rolling 3-year means. The three-year mean data are provided for two ecosystem types within each grid cell (short vegetation and forest/woodland, as discussed above). Deposition rates are given on a per-area basis (e.g. kg N ha-1 yr-1).
References
Beswick, K.M., Choularton, T.W., Inglis, D.W.F., Dore, A.J. & Fowler, D. 2003. Influences on long-term trends in ion concentration and deposition at Holme Moss. Atmospheric Environment, 37 (14), 1927-1940.
Braban, C.F., Stephens, A.M., Tang, Y.S., Twigg, M.M., Leeson, S.R., Jones, M.R., Simmons, I., Harvey, D., Kentisbeer, J., van Dijk, N., Nemitz, E., Roberts, E., Leaver, D., Andres, C., Smith, R., Banin, L., Sleep, D., Poskitt, J., Carter, H.T., Thacker, S., Patel, M., Tanna, B., Keenan, P.O., Pereira, G., Lawlor, A.J., Warwick, A., Farrand, P., Sutton, M.A. (2021) UK Eutrophying and Acidifying Atmospheric Pollutant project’s National Ammonia Monitoring Network (NAMN). https://ukair.defra.gov.uk/networks/network-info?view=nh3.
Conolly, C., Vincent, K., Sanocka, A., Richie, S., Knight, D., Halser, S., Donovan, B., Osbourne, E., Sampford, A., Braban, C.F., Stephens, A.M., Tang, Y.S., Twigg, M.M., Leeson, S.R., Jones, M.R., Simmons, I., Harvey, D., Kentisbeer, J., van Dijk, N., Nemitz, E., Roberts, E., Leaver, D., Andres, C., Smith, R., Banin, L., Sleep, D., Poskitt, J., Carter, H.T., Thacker, S., Patel, M., Tanna, B., Keenan, P.O., Pereira, G., Lawlor, A.L., Warwick, A., Farrand, P., Sutton, M.A. (2018) UKEAP 2018 Annual report. Prepared for the Environment Agency & Defra and the devolved administration by NERC Centre for Ecology & Hydrology & Ricardo Environment and Energy. 64 pp. https://uk-air.defra.gov.uk/assets/documents/reports/cat09/2109211306_UKEAP_annual_report_2018.pdf.
Dore, A.J., Choularton, T.W. & Inglis, D.W.F. 2001. Monitoring studies of precipitation and cap cloud chemistry at Holme Moss in the Southern Pennines. Water, Air and Soil Pollution: Focus 1; 381-390.
Fowler, D., Cape, J.N., Leith, I.D., Choularton, T.W., Gay, M.J. & Jones, A. 1988. The influence of altitude on rainfall composition at Great Dun Fell. Atmospheric Environment, 22, 1355-1362.
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz-Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmons, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., De Chiara, G., Dahlgren, P., Dee, D., Diamantakis, M., Dragani, R., Flemming, J., Forbes, R., Fuentes, M., Geer, A., Haimberger, L., Healy, S., Hogan, R. J., Hólm, E., Janisková, M., Keeley, S., Laloyaux, P., Lopez, P., Lupu, C., Radnoti, G., de Rosnay, P., Rozum, I., Vamborg, F., Villaume, S., and Thépaut, J.-N.: The ERA5 global reanalysis, Quarterly Journal of the Royal Meteorological Society, 146, 1999–2049, https://doi.org/10.1002/qj.3803, 2020.
RoTAP. 2012. Review of Transboundary Air Pollution: Acidifcation, Eutrophication, Ground Level Ozone and Heavy Metals in the UK. Contract Report to the Department for Environment, Food and Rural Affairs. Centre for Ecology and Hydrology. www.rotap.ceh.ac.uk
Smith, R.I., Fowler, D., Sutton, M.A., Flechard, C. & Coyle, M. 2000. Regional estimation of pollutant gas deposition in the UK: model description, sensitivity analyses and outputs. Atmospheric Environment, 34, 3757-3777.
Skamarock, W.C., Klemp, J.B., Dudhia, J., Gill, D.O., Liu, Z., Berner, J., Wang, W., Powers, J.G., Duda, M.G., Barker, D.M., et al. (2019). A Description of the Advanced Research WRF Model Version 4. UCAR/NCAR.
Simpson, D., Benedictow, A., Berge, H., Bergström, R., Emberson, L.D., Fagerli, H., Flechard, C.R., Hayman, G.D., Gauss, M., Jonson, J.E., et al. (2012). The EMEP MSC-W chemical transport model – technical description. Atmos. Chem. Phys. 12, 7825–7865.
Stedman, J.R., Kent, A.J., Grice, S., Bush, T.J. & Derwent, R.G. 2007. A consistent method for modelling PM10 and PM2.5 concentrations across
Vieno, M., Heal, M.R., Williams, M.L., Carnell, E.J., Nemitz, E., Stedman, J.R., and Reis, S. (2016). The sensitivities of emissions reductions for the mitigation of UK PM2.5. Atmos. Chem. Phys. 16, 265–276.
The Concentration Based Estimated Deposition (CBED) methodology generates 5x5 km resolution gridded data of wet and dry deposition of sulphur, oxidised and reduced nitrogen, and base cations from measured concentrations of gases and particulate matter in air and measured concentrations of ions in precipitation. These data are collected at sites in the UK Eutrophying and Acidifying Pollutants (UKEAP) network. The site-based measurements are first interpolated to generate maps of concentrations for the UK. The ion concentrations in precipitation are combined with an annual precipitation map from the UK Meteorological Office to generate values of wet deposition. Gas and particulate matter concentration maps are combined with spatially distributed estimates of habitat-specific deposition velocities to generate dry deposition for 5 land cover categories: forest, moorland, grassland, arable and urban. The deposition to the 5 land cover categories are combined, depending on the relative proportions of different land cover categories in the 5x5 km grid square, to generate values for grid square averaged deposition. Dry deposition includes deposition of gases (Sulphur Dioxide (SO2), Nitric Acid (HNO3), Nitrogen Dioxide (NO2) and Ammonia (NH3) and particulate matter (sulphate, nitrate, ammonium, calcium and magnesium) to vegetation. For critical load exceedance calculations, deposition values for moorland are applied to all non-woodland habitats, and deposition values for forest are applied to all woodland habitats.
The values for SO2 concentration are calculated from rural measurements of SO2 and uses an urban enhancement factor. For oxidised nitrogen dry deposition, nitric acid concentrations are calculated by interpolation of measurements from about 30 sites and NO2 concentrations are taken for the Pollution Concentration Mapping (PCM) model (Stedman et al., 2007). This latter data set includes a combination of interpolation of measurements from rural sites combined with modelling concentrations from point sources and line sources. Ammonia concentrations are taken from a combination of the FRAME atmospheric chemical transport model (Singles et al., 1998; Fournier et al., 2003; Dore et al., 2007) and the annual measured concentrations from the UKEAP network, where the former generates the local scale variability that cannot be derived from the network measurement data on their own.
Wet deposition includes deposition from precipitation as well as direct deposition of cloud droplets to vegetation (known as ‘occult’ deposition) and is mapped for sulphate, ammonium, nitrate, calcium, magnesium, and acidity (hydrogen ion). The separation of anthropogenic (non-seasalt) and total components of sulphur and calcium is calculated using ion ratios relative to sodium in sea water. Mapping wet deposition includes an orographic enhancement factor for the concentration of precipitation in upland regions due to the seeder-feeder effect. The enhancement factor is taken from observations of the increase in ion concentrations with altitude observed at Great Dun Fell in the Northern Pennines (Fowler et al., 1988) and subsequently confirmed by measurements at Holme Moss in the southern Pennines (Dore et al., 2001 ; Beswick et al., 2003).
Significant inter-annual variations in deposition can occur due to the natural variability in annual weather patterns including precipitation which directly influences wet deposition. The general circulation of the air, temperature and precipitation also affect emissions, atmospheric chemistry and transport, so adjusting the influence of different pollution sources on the measured concentrations at the network sites. The CBED deposition data used to calculate the exceedance of critical loads are therefore averaged over a three year period. This has been demonstrated to be a suitable time period to smooth out some of the inter-annual variations in deposition.
Data are calculated on an annual basis but provided as rolling 3-year means. The 3-year mean data are ecosystem-specific providing two sets of values: (i) assuming moorland/short vegetation everywhere; (ii) assuming forest everywhere. Additionally grid average are provided as 3-year rolling means.
Beswick, K.M., Choularton, T.W., Inglis, D.W.F., Dore, A.J. & Fowler, D. 2003. Influences on long-term trends in ion concentration and deposition at Holme Moss. Atmospheric Environment, 37 (14), 1927-1940.
Dore, A.J., Choularton, T.W. & Inglis, D.W.F. 2001. Monitoring studies of precipitation and cap cloud chemistry at Holme Moss in the Southern Pennines. Water, Air and Soil Pollution: Focus 1; 381-390.
Dore, A. J.; Vieno, M.; Tang, Y. S.; Dragosits, U.; Dosio, A.; Weston, K. J.; Sutton, M. A.. (2007) Modelling the atmospheric transport and deposition of sulphur and nitrogen over the United Kingdom and assessment of the influence of SO2 emissions from international shipping. Atmospheric Environment, 41 (11). 2355-2367. doi:10.1016/j.atmosenv.2006.11.013
Fournier, N.; Pais V.A.; Sutton M.A.; Weston K.J.; Dragosits U.; Tang S.Y. and Aherne J. (2003) Parallelisation and application of a multi-layer atmospheric transport model to quantify dispersion and deposition of ammonia over the British Isles. Environmental Pollution, 116(1), 95-107.
Fowler, D., Cape, J.N., Leith, I.D., Choularton, T.W., Gay, M.J. & Jones, A. 1988. The influence of altitude on rainfall composition at Great Dun Fell. Atmospheric Environment, 22, 1355-1362.
RoTAP. 2012. Review of Transboundary Air Pollution: Acidifcation, Eutrophication, Ground Level Ozone and Heavy Metals in the UK. Contract Report to the Department for Environment, Food and Rural Affairs. Centre for Ecology and Hydrology. www.rotap.ceh.ac.uk
Singles, R., M.A. Sutton & K.J. Weston (1998) A multi-layer model to describe the atmospheric transport and deposition of ammonia in Great Britain. Atmos. Environ., 32, 393-399.
Smith, R.I., Fowler, D., Sutton, M.A., Flechard, C. & Coyle, M. 2000. Regional estimation of pollutant gas deposition in the UK: model description, sensitivity analyses and outputs. Atmospheric Environment, 34, 3757-3777.
Stedman, J.R., Kent, A.J., Grice, S., Bush, T.J. & Derwent, R.G. 2007. A consistent method for modelling PM10 and PM2.5 concentrations across
Resource locators
URL: http://www.pollutantdeposition.ceh.ac.uk/ukeap
Title: UK Acidifying and Eutrophying Atmospheric Pollutants
Description: Supporting information
Function: information
URL: https://uk-air.defra.gov.uk/networks/network-info?view=ukeap
Title: UK Acidifying and Eutrophying Atmospheric Pollutants
Description: Supporting information
Function: information
Fieldwork and/or Laboratory Instrumentation: N/A
Calibration Steps and Values: N/A
Nature and Units of Recorded Values
All deposition values are expressed as kilo-equivalents per hectare per year (keq ha-1 year-1). The values can be converted to kilograms of sulphur or nitrogen per hectare per year by:
(a) sulphur deposition: multiply values in keq ha-1 year-1 by 16 to give kg S ha-1 year-1
(b) oxidised and/or reduced nitrogen deposition: multiply values in keq ha-1 year-1 by 14 to give kg N ha-1 year-1.
(c) combined base cation deposition (Ca+Mg) is expressed as calcium equivalents: multiply values in keq ha-1 year-1 by 20 to give kg Ca ha-1 year-1.
The Concentration Based Estimated Deposition (CBED) methodology generates 5x5 km resolution gridded data of wet and dry deposition of sulphur, oxidised and reduced nitrogen, and base cations from measured concentrations of gases and particulate matter in air and measured concentrations of ions in precipitation. These data are collected at sites in the UK Eutrophying and Acidifying Pollutants (UKEAP) network. The site-based measurements are first interpolated to generate maps of concentrations for the UK. The ion concentrations in precipitation are combined with an annual precipitation map from the UK Meteorological Office to generate values of wet deposition. Gas and particulate matter concentration maps are combined with spatially distributed estimates of habitat-specific deposition velocities to generate dry deposition for 5 land cover categories: forest, moorland, grassland, arable and urban. The deposition to the 5 land cover categories are combined, depending on the relative proportions of different land cover categories in the 5x5 km grid square, to generate values for grid square averaged deposition. Dry deposition includes deposition of gases (Sulphur Dioxide (SO2), Nitric Acid (HNO3), Nitrogen Dioxide (NO2) and Ammonia (NH3) and particulate matter (sulphate, nitrate, ammonium, calcium and magnesium) to vegetation. For critical load exceedance calculations, deposition values for moorland are applied to all non-woodland habitats, and deposition values for forest are applied to all woodland habitats.
The values for SO2 concentration are calculated from rural measurements of SO2 and uses an urban enhancement factor. For oxidised nitrogen dry deposition, nitric acid concentrations are calculated by interpolation of measurements from about 30 sites and NO2 concentrations are taken for the Pollution Concentration Mapping (PCM) model (Stedman et al., 2007). This latter data set includes a combination of interpolation of measurements from rural sites combined with modelling concentrations from point sources and line sources. Ammonia concentrations are taken from a combination of the FRAME atmospheric chemical transport model (Singles et al., 1998; Fournier et al., 2003; Dore et al., 2007) and the annual measured concentrations from the UKEAP network, where the former generates the local scale variability that cannot be derived from the network measurement data on their own.
Wet deposition includes deposition from precipitation as well as direct deposition of cloud droplets to vegetation (known as ‘occult’ deposition) and is mapped for sulphate, ammonium, nitrate, calcium, magnesium, and acidity (hydrogen ion). The separation of anthropogenic (non-seasalt) and total components of sulphur and calcium is calculated using ion ratios relative to sodium in sea water. Mapping wet deposition includes an orographic enhancement factor for the concentration of precipitation in upland regions due to the seeder-feeder effect. The enhancement factor is taken from observations of the increase in ion concentrations with altitude observed at Great Dun Fell in the Northern Pennines (Fowler et al., 1988) and subsequently confirmed by measurements at Holme Moss in the southern Pennines (Dore et al., 2001 ; Beswick et al., 2003).
Significant inter-annual variations in deposition can occur due to the natural variability in annual weather patterns including precipitation which directly influences wet deposition. The general circulation of the air, temperature and precipitation also affect emissions, atmospheric chemistry and transport, so adjusting the influence of different pollution sources on the measured concentrations at the network sites. The CBED deposition data used to calculate the exceedance of critical loads are therefore averaged over a three year period. This has been demonstrated to be a suitable time period to smooth out some of the inter-annual variations in deposition.
Data are calculated on an annual basis but provided as rolling 3-year means. The 3-year mean data are ecosystem-specific providing two sets of values: (i) assuming moorland/short vegetation everywhere; (ii) assuming forest everywhere. Additionally grid average are provided as 3-year rolling means.
Beswick, K.M., Choularton, T.W., Inglis, D.W.F., Dore, A.J. & Fowler, D. 2003. Influences on long-term trends in ion concentration and deposition at Holme Moss. Atmospheric Environment, 37 (14), 1927-1940.
Dore, A.J., Choularton, T.W. & Inglis, D.W.F. 2001. Monitoring studies of precipitation and cap cloud chemistry at Holme Moss in the Southern Pennines. Water, Air and Soil Pollution: Focus 1; 381-390.
Dore, A. J.; Vieno, M.; Tang, Y. S.; Dragosits, U.; Dosio, A.; Weston, K. J.; Sutton, M. A.. (2007) Modelling the atmospheric transport and deposition of sulphur and nitrogen over the United Kingdom and assessment of the influence of SO2 emissions from international shipping. Atmospheric Environment, 41 (11). 2355-2367. doi:10.1016/j.atmosenv.2006.11.013
Fournier, N.; Pais V.A.; Sutton M.A.; Weston K.J.; Dragosits U.; Tang S.Y. and Aherne J. (2003) Parallelisation and application of a multi-layer atmospheric transport model to quantify dispersion and deposition of ammonia over the British Isles. Environmental Pollution, 116(1), 95-107.
Fowler, D., Cape, J.N., Leith, I.D., Choularton, T.W., Gay, M.J. & Jones, A. 1988. The influence of altitude on rainfall composition at Great Dun Fell. Atmospheric Environment, 22, 1355-1362.
RoTAP. 2012. Review of Transboundary Air Pollution: Acidifcation, Eutrophication, Ground Level Ozone and Heavy Metals in the UK. Contract Report to the Department for Environment, Food and Rural Affairs. Centre for Ecology and Hydrology. www.rotap.ceh.ac.uk
Singles, R., M.A. Sutton & K.J. Weston (1998) A multi-layer model to describe the atmospheric transport and deposition of ammonia in Great Britain. Atmos. Environ., 32, 393-399.
Smith, R.I., Fowler, D., Sutton, M.A., Flechard, C. & Coyle, M. 2000. Regional estimation of pollutant gas deposition in the UK: model description, sensitivity analyses and outputs. Atmospheric Environment, 34, 3757-3777.
Stedman, J.R., Kent, A.J., Grice, S., Bush, T.J. & Derwent, R.G. 2007. A consistent method for modelling PM10 and PM2.5 concentrations across
Resource locators
URL: http://www.pollutantdeposition.ceh.ac.uk/ukeap
Title: UK Acidifying and Eutrophying Atmospheric Pollutants
Description: Supporting information
Function: information
URL: https://uk-air.defra.gov.uk/networks/network-info?view=ukeap
Title: UK Acidifying and Eutrophying Atmospheric Pollutants
Description: Supporting information
Function: information
Fieldwork and/or Laboratory Instrumentation: N/A
Calibration Steps and Values: N/A
Nature and Units of Recorded Values
All deposition values are expressed as kilo-equivalents per hectare per year (keq ha-1 year-1). The values can be converted to kilograms of sulphur or nitrogen per hectare per year by:
(a) sulphur deposition: multiply values in keq ha-1 year-1 by 16 to give kg S ha-1 year-1
(b) oxidised and/or reduced nitrogen deposition: multiply values in keq ha-1 year-1 by 14 to give kg N ha-1 year-1.
(c) combined base cation deposition (Ca+Mg) is expressed as calcium equivalents: multiply values in keq ha-1 year-1 by 20 to give kg Ca ha-1 year-1.