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AQC helps JNCC to Predict the future for Nitrogen Deposition in the UK


Air Quality Consultants Ltd formed part of the JNCC ‘Nitrogen Futures’ project team. The project predicted the rate of change to nitrogen deposition by 2030 and beyond. It showed that rather than through national measures, additional improvements might sensibly be delivered by targeting measures on key areas close to designated sites.

Air Quality Consultants Ltd formed part of the project team which assessed the potential to control nitrogen deposition on conservation sites.

The Joint Nature Conservation Committee (JNCC) today published this evidence which shows how local action can be the most effective way to protect nature conservation sites from nitrogen pollution.

The ‘Nitrogen Futures’ project assessed different approaches to controlling nitrogen deposition on conservation sites and showed that rather than through national measures to reduce nitrogen pollution, cost effective improvements might sensibly be delivered by targeting measures on key areas close to the designated sites. 

The harmful effects that excess nitrogen deposition can have on biodiversity are well understood.  In recent years, there have been several high-profile planning cases which have explored, and clarified, how air quality issues should be treated within the European Habitats Directive, and UK Habitats Regulations.  In particular, issues around Ashdown Forest and Epping Forest, with which Air Quality Consultants Ltd has been involved, has increased the recognition that effects of air quality on biodiversity can determine whether or not new development can go ahead.

Critical levels and critical loads, which have been set to protect sensitive ecological features, are currently exceeded in many parts of the UK.  The project for JNCC has forecast how this might change by 2030 and beyond.  It has then considered whether additional improvements might best be achieved by targeting specific emissions sources close to the designated habitats, or whether further national-level emissions reductions would be more cost effective.

The results show that achieving the UK-wide emissions reductions targets, which are set under the National Emissions Ceiling Regulations, will deliver an overall reduction in nitrogen deposition to priority habitats of 17% by 2030.  There will, however, continue to be significant exceedances of the critical levels and critical loads across much of the UK beyond 2030.

In terms of reducing nitrogen deposition, targeting measures on localised zones surrounding each sensitive site (e.g. each Site of Special Scientific Interest (SSSI)) will be almost as effective as applying further national-level emissions reductions, but will cost less.  Those targeted measures that will be most effective will depend on which sources contribute most to a site.  For example, targeting transport emissions would achieve little to reduce nitrogen deposition to a remote site which is well away from any roads but surrounded by agriculture.  Similarly, targeting local agricultural emissions would not drive improvements where road traffic is the dominant local source of nitrogen deposition.

The report highlights the importance of spatial averaging when determining effects.  National-level modelling (on a 5 km x 5 km or 1 km x 1 km basis) might mask exceedances of the critical levels or critical loads close to emissions sources (for example near to roads).  Similarly, different mitigation measures might be required to drive improvements to the worst-case locations than would be suggested by coarse, national-scale models.  This highlights the importance of local-scale assessment where there are emissions sources very close to a site.

The project was led by UK Centre of Ecology and Hydrology (CEH).  Air Quality Consultants Ltd formed part of the team alongside Rothamsted Research, Aether, Lancaster University, and Manchester Metropolitan University.  It built on an earlier analysis carried out by Air Quality Consultants Ltd to highlight the importance of traffic-related ammonia to roadside nitrogen deposition.  In particular, it was shown that some conventional measures which target NOx emissions from road traffic might actually increase nitrogen deposition.  Air Quality Consultants Ltd has produced a tool for predicting ammonia emissions from road traffic which was used during the JNCC Nitrogen Futures Project.  More information on the Nitrogen Futures project is given here.

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