Ammonium background values in the groundwater of Lower Saxony 1: 500,000 (WMS Service)

Background values for dissolved ammonium in groundwater have been determined for the hydrogeological subregions of Lower Saxony (Elbracht et al., 2016) in order to fulfil the tasks of the EC Water Framework Directive (EC-WRRL) and the Groundwater Ordinance (GrwV). The background values of dissolved ammonium include the levels that occur under natural conditions due to the contact of the groundwater with the surrounding rock matrix of the aquifer. The map shows the ammonium background values of the hydrogeological subregions of Lower Saxony. The classification is based on the valid de minimis thresholds (GFS) of the National Working Group Water (LAWA), the limit values of the Drinking Water Ordinance (TrinkwV) and the World Health Organisation (WHO) benchmarks. By selecting a subspace you get further information (e.g. number of samples, combined sub-spaces, etc.). Background values are not current values for groundwater quality and cannot be used as such! Information on the data: The groundwater analyses used are derived from the database of the Lower Saxony Soil Information System (NIBIS). Background values are defined as the 90th percentile of the normal population of the geogenic concentration of the analysed parameter. The most up-to-date analysis of a groundwater measuring site was used to determine the background values, but no measurements dating before 2000. In the case of too low sample numbers (n < 10), lithologically similar subspaces were combined to form a common background value. The calculation of the background values followed the method for statistical evaluation of the data using the probability network of the State Geological Services (Wagner et al., 2011). Sources: ELBRACHT, J., MEYER, R. &AMP; REUTTER, E. (2016): Hydrogeological rooms and sub-rooms in Lower Saxony. — Georeports 3, LBEG, Hannover. DOI: 10.48476/geober_3_2016 WAGNER, B., WALTER, T., HIMMELSBACH, T., CLOS, P., BEER, A., BUDZIAK, D., DREHER, T., FRITSCHE, H.-G., HÜBSCHMANN, M., MARCZINEK, S., PETERS, A., POESER, H., SCHUSTER, H., STEINEL, A., WAGNER, F. &AMP; WIRSING, G. (2011): Hydrogeochemical Background values of the groundwaters of Germany as a web map service. — Groundwater 16(3): 155-162; Springer, Berlin/Heidelberg.