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Emission Source Attribution Project

The Source Attribution project will update the estimate of the types of emissions contributing to a specific protected area or UK grid square on the Air Pollution Information System (APIS). The work is being undertaken as part of the APIS partnership.

Project aims

A piechart showing a source attribution example from APIS website. The chart shows that the primary source of emissions contributing to nitrogen deposition at Lough Navar in Northern Ireland are European import (37%) and Livestock (35%)

The current source attribution dataset on APIS helps users understand what emission sources are reaching a specific protected area and how much each sector is contributing. The estimates include long and short range emissions as well as breakdowns by sector and type of nitrogen. The dataset can also be found on UK Centre for Ecology and Hydrology’s Environmental Information Data Centre and via

This project updates the existing 2012 dataset to account for the emission sources operating now. For example, more than half of the UK coal-fired power stations have shut down since 2012. This represents a major change in the types of emissions reaching some protected areas.

What will change on APIS?

APIS will continue to provide a searchable database with information about air pollutants and their impacts on habitats and species. The primary change will be addition of a new source attribution dataset on the search by site or location tab.

All advice about UK protected sites including their sensitivity to air pollution, average pollutant concentrations and deposition on the site will be provided as usual.


How is source attribution estimated?

EMEP (European Monitoring and Evaluation Program) and CBED (Concentration Based Estimated Deposition) models will be used to predict concentrations and deposition at specific sites. This may be familiar from the annually updated 3-year average concentration and deposition datasets available in the Site Search and Search by Location tools.

A national estimate of emissions from each sector is made as part of the National Atmospheric Emissions Inventory. In the annually updated concentration and deposition figures on APIS, all sectors are effectively included in the modelling as a bulk total for emissions from the UK and abroad. For source attribution, several model runs are required. Each sector is removed from a run to show the concentration and deposition result if it was not present. The sector contribution is then estimated by comparing its result to the total contribution at the relevant grid square or protected area.


Why has it been so long since the last update?

There are 42 sectors in the current source attribution dataset and that means a lot of model runs. For each sector, the contribution at each grid square is estimated by comparing to the total for all emission sources. This extra effort is also why the dataset is not updated annually like the modelling for total UK emissions. 

It would be helpful to hear what frequency of update you'd like to see.


Where can I get more information?

Information about modelling used on APIS is available on the current modelling and source attribution pages.


How can I contribute?

JNCC would love to hear how you use the current source attribution dataset and any suggested changes to the sector breakdown or data format that would make it easier to use.

Join the JNCC Air Pollution Project Stakeholder list to express interest or share your ideas and experiences.



Air Pollution

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