About Biodiversity


Since the rejection of the PAS legislation by the Council of State in May 2019, the Netherlands has been faced with the challenge of substantially reducing nitrogen emissions. This concerns the emissions of ammonia (NH3) and nitrogen oxides (NOx). Precipitation of these substances in nature (deposition) can lead to a reduction of biodiversity. They also have a negative impact on air quality.

Our knowledge of nitrogen emissions currently contains a number of uncertainties. Emissions are measured at source only to a very limited extent. Their transport by air is also measured to a limited extent. This applies in particular to ammonia, which is responsible for about 60% of Dutch emissions. Other countries in Europe like Germany, Italy, UK and Denmark face similar issues and need for measurement data on ammonia is expected to become more urgent in the years ahead. Recent NASA studies highlight ammonia emission are on the rise in many other parts of the world incl. Africa and China.


Clear Air is focused on

  • Routine and high resolution monitoring of emissions and sinks of NOx and NH3
  • Development of innovative satellite instruments to improve pollution monitoring
  • Integration in model system that calculates nitrogen deposition
  • Use other EO data (like e.g. vegetation, or fluorescence) to improve model based prediction of deposition

Research activities include amongst others

  • Understand temporal changes in emissions, in particular for ammonia
  • Improve spatial scales of emissions
  • Earth observation instrument development including for measuring emission at spatial resolution better than 1000m
  • Improve the understanding and methods of prediction how these species act as pre-cursors to aerosols
  • Include the impact of species that lead to acidification (SO2), their interaction with mineral dust, in addition to nutrification on biodiversity


The work of Clear Air results in data to design and monitor emission reduction policies, thereby reducing harmful deposition of nitrogen in protected nature areas (Natura2000) and, as a result, increase biodiversity. This policy represents significant economic value and impacts permits for industry, airports, building and large infrastructure expansions like roads.


Ammonia is measured on an hourly basis at locations of the National Measurement Network (LML). Satellites can provide near daily data that can be used to improve our understanding in the spatial distribution of ammonia over the Netherlands and thereby improve deposition prediction. This map (TNO/ECCC) shows satellite measurement of the average ammonia concentration (mg/m2) in the atmosphere of the Netherlands for the year 2017 based on CrIS (NASA/NOAA) satellite data. On the map you can see higher ammonia concentrates in the eastern part, and lower concentrates in the western part of The Netherlands.

This map shows ammonia concentrates in The Netherlands for the year 2017. In the eastern part of the Netherlands, the data shows higher concentrates. In the western part of the Netherlands, the data show lower concentrates.

Areas of research

The research and technology development work of Clear is focused on three main areas.

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