Site Relevant Critical Loads and Source Attribution

New APIS Tool

A new APIS GIS map tool for Site Relevant Critical Loads & Search by Location has been developed in place of the look-up system below. For the first time we have added 1km datasets for Ammonia and N and Acid Deposition. 

enter app

Note on the new 1km data (2018-2020): To calculate the pollutant maps for Ammonia, Nitrogen and Acid Deposition we are now using a new transport model (EMEP4UK) to calculate the ammonia footprint for the UK. This output is then calibrated to our ammonia measurement network data. You will notice some spatial changes in concentrations and depositions across the UK. In general the change has meant some elevated concentrations between the 1-3 ug/m3 range, but large parts of the UK have remained unchanged. A full report on the analysis of the change in model will be released soon and shared on APIS.

We welcome any comments or suggestions that you may have about the new APIS interface, you can suggest your changes or report any problems and select the option "APIS bugs & broken links".

To see a video demonstration on how to use this tool go here.

If you wish to keep using the look-up tables below then we are making that available until the new tool 'beds in'.

We encourage you to use the APIS app above where Source Attribution and site pollutant trends now resides. The simple lookup tool below will continue to run only up to July 31st 2022.

Data Update 11/05/2022: The pollution concentration and deposition data in the Site Relevant Critical Load Tool has been updated to use the 3-year mean for the years 2018-20.

About the Site Relevant Critical Loads Tool

The ‘Site Relevant Critical Loads’ tool provides critical loads for acidity and nitrogen for designated features within every SAC, SPA or A/SSSI in the UK. You can view an overview of each interest feature for each site. Critical loads are assigned to each sensitive feature for either nutrient nitrogen or acidity. Furthermore, deposition data for nitrogen and sulphur at each site are provided, apportioned to major sources, and presented in pie charts. You can also select a grid reference if you know the exact location of your feature within a site. Simply follow the screen below.

Search by SiteSelect a designation type and select 'Next'


Devon SAC
East Devon Pebblebed Heaths SAC
[photo: Clinton Devon Estates]