Abstract

The National Institute for Public Health and the Environment (RIVM) manages the AERIUS calculation tool that calculates and monitors how much nitrogen is deposited on the soil in the Netherlands. AERIUS Calculator is one of its components. Government bodies and project initiators use this tool to calculate the emission of nitrogen and how much of it is deposited on Nature 2000 areas. Competent authorities use Calculator as a tool for granting permits.

These calculations must be accurate to ensure that policymakers and licensing authorities take the correct decisions. To ensure that this is the case, the latest scientific insights and updated data are entered into AERIUS. The results of the updated calculator can therefore differ from the results provided by the previous version. RIVM carried out the impact analysis discussed here in order to evaluate the effects of the update. The most important differences and their effect on calculations were analysed to do this.

The update is needed because the data on nitrogen emissions changes regularly. This time around, the so-called emission factors for traffic and mobile vehicles were updated, among other matters. AERIUS uses these emission factors in order to determine the nitrogen emission of a project. In addition, the calculation models used by AERIUS were updated. That also applies to nature-related data such as the borders of nitrogen-sensitive nature in the Nature 2000 areas (the so-called habitat maps). As a result of this update, the locations used in AERIUS Calculator for the calculations also change (the relevant hexagons). The map with the total calculated deposition of nitrogen (background deposition) is also better in line with the measurements.