Heavy metals in fresh surface water in the Netherlands
Developments
Heavy metals bond to a greater or lesser extent to suspended matter. The concentrations of heavy metals in fresh surface water are decreasing over time, even if the pattern is sometimes rather unpredictable. In 2002, chrome, mercury, cadmium and lead conformed with the MAC virtually everywhere, and with the negligible risk level (the desired quality standard) in a large number of cases. Nickel and zinc exceed the MAC in the Maas River by a considerable degree. Copper is below the MAC in only a small number of locations.
- See also http://www.waterinbeeld.nl/wib2004.
Policy
The aim of the policy is to reduce the levels of metals to below the MAC (maximum acceptable concentration) and, in the slightly longer term (if possible before 2010) to below the negligible risk level (the desired quality standard).
Relevance
The values for the MAC are based on ecotoxicological considerations. That means that, when the MAC is exceeded, negative effects on organisms cannot be excluded. As a rule, the negligible risk, or the desired quality standard, is 100 times lower than the MAC.
Monitoring sites
- The monitoring sites in the rivers are sites chosen by the Commissie Integraal Waterbeheer/Commissie Uitvoering Wet Verontreiniging Oppervlaktewater (CIW/CUWVO). There are approximately 250 monitoring sites in regionally managed waters.
- For bodies of water under national management a group of monitoring sites was compiled from 25 representative sites selected from the entire monitoring network for those water bodies. It includes sites in the Rhine, Maas, Scheldt, IJssel, IJsselmeer and in a number of canals and lakes.
