The determination of Critical Loads for the protection of ecosystems against adverse effects of atmospheric pollutants is one of the major tasks of the Coordination Centre for Effects (CCE). Critical loads are currently available for 41 European countries and were obtained based on two different sources:
- Call for Data - National data submitted by National Focal Centres (NFCs)
- European background database (EU-DB) calculated by the CCE
Ideally, the critical loads are based on national data submitted by NFCs upon a Call for Data. The Call for Data is an instrument for the compilation of critical load and level data from the NFCs. It contains the instructions on how to calculate the required values and how to submit the results to the CCE. The latest Call for Data was issued in the autumn of 2015 with a deadline in 2017. The main objectives of the last Call were to update the critical loads of acidification (SMB model), eutrophication (CLnutN from SMB or CLempN), and the critical loads of nitrogen and sulphur for the protection of plant species diversity. The official letter from the Call for Data 2015-2017 can be downloaded here.
For those countries which did not submit national data, the critical loads were calculated based on values from the European background database (EU-DB). The EU-DB is maintained by the CCE in collaboration with Wageningen Environmental Research (Alterra).
The very simple dynamic soil acidification model - VSD model - has been developed as the simplest extension of the Simple Mass Balance (SMB) steady-state model for critical load calculations and with an eye on regional applications. It is designed to simulate the acidification (and recovery) of non-calcareous (unmanaged) soils. It consists of a set of mass balance equations describing the soil input–output relationships and equations describing rate-limited and equilibrium soil processes. A single-site version can be downloaded here (version of 7 July 2017).
The VSD+ model is an extension of the VSD model with detailed C and N dynamics. The model was developed in order to calculate the effects of atmospheric deposition and climate change on soil acidification, nutrient availability and carbon sequestration. Simulated values for pH and nitrogen such as C/N ratio and nitrate concentration can be used in models that predict occurrence probabilities of plant species as a function of abiotic conditions. A single-site version can be downloaded here (version of 22 September 2017).
The MetHyd model is a meteo-hydrological pre-processor for the VSD+ and VSD models. A single-site version can be downloaded here (version of 13 January 2017).
The GrowUp model is a pre-processor for VSD+ and VSD to compute N and base cation uptake from user specified tree-growth inputs. A single-site version can be downloaded here (version of 12 July 2017).