Quality of shallow and medium-deep groundwater in the Netherlands : In 2008 and changes in the quality during the period 1984-2008
De kwaliteit van ondiep en middeldiep grondwater in Nederland : In het jaar 2008 en de verandering daarvan in 1984-2008
05 July 2012, PDF |
196 pages |
van Vliet ME, Vrijhoef A, Boumans LJM, Wattel-Koekkoek EJW
RIVM Report 680721005
The levels of ammonium, total phosphorus (total P), nitrate, potassium, nickel, cadmium, zinc, chromium, arsenic, sulphate, chloride, aluminium and pH measured in shallow and medium-deep groundwater in the Netherlands in 2008 exceed the environmental quality objectives. The quality of the groundwater has not changed remarkably between 1984 and 2008. Both decreases and increases in the quality of shallow and medium-deep groundwater in sandy areas have been observed. Improvements in water quality may be due to a lower use of fertilizer, lower quantities of heavy metals entering the groundwater via atmospheric precipitation and reduced surface spreading of animal manure. These are the major conclusions of a study carried out by the RIVM by order of the Ministry of Housing, Spatial Planning and the Environment (VROM). Many environmental quality objectives are exceeded in sandy areas. Increased values are particularly prevalent in shallow groundwater in sandy areas in the south of the Netherlands and the Peelhorst area and in river terraces along the Meuse River. The high concentrations of total P and ammonium in these river areas likely result from the degradation of organic material. These areas also contain high concentrations of naturally occurring arsenic. The concentrations of chloride and potassium in marine clay and peat areas are high due to the influence of the sea. Similarities between shallow and mediumdeep groundwater in 'polders' (e.g. reclaimed land) and in marine clay areas suggest that ammonium is released as a result of organic matter degradation. The high concentrations of chloride, sulphate and potassium in the medium-deep groundwater in sand dunes and barrier beaches are influenced by brackish water in the subsoil. The most likely explanation for high concentrations of ammonium and total P in both shallow and medium-deep groundwater is the degradation of organic matter.