Peak Matching offers view of nitrogen deposition and evaporation

Information about nitrogen and evaporation is essential for the sustainable management of groundwater resources and nature in the dunes. In this research project, a method is being tested to retrospectively measure the nitrogen deposition and evaporation through the analysis of the drill-cores of dune soils.

Need for measurement data

The themes of nitrogen deposition and of drought caused by climate change are high on the political agenda, and both have an impact on nature and water quality in the dunes. Nitrogen deposition is particularly important in a number of nature areas that are managed by the drinking water utilities in dune areas. Quality data on this question are however lacking. The same applies to evaporation: a significant part of the water balance in the catchment area is being heavily impacted by climate change. In this project a method is being tested to reconstruct the evolution of the evaporation.

Reconstruction of evaporation and nitrogen deposition

The pore-water profile in high dunes with a thick unsaturated zone provides an archive in which one can look back 30 years in time. At one site in the Amsterdam water supply dunes, the evolution of evaporation and deposition over the last few decades is being reconstructed. This method involves taking drill-cores on a high dune with a thick unsaturated zone, and conducting chemical analyses on the soil humidity that is expelled from these cores. Using Chloride Peak Matching, one can determine the subsurface transport time, average groundwater recharge and nitrogen deposition.

Insight into future developments

The results of the test measurements can be used as a reference for the current situation and, through a trend analysis, provide insight into future developments, so that better-founded choices can for example be made in nature and water management. In addition, the nitrogen deposition data can be used to underpin policy measures aimed at limiting nitrogen.

The method can also be applied in other nature areas in the Netherlands and abroad. This refers principally to the European dune grasslands, which serve as a future reference framework for the effects of climate change in the Netherlands, and for which there are at the moment insufficient deposition measurement series.

Amsterdam water supply dunes

Amsterdam water supply dunes.