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.

Technical note

The concentrations of the heavy metals are obtained from the national and regional water authorities every year. The total concentration of heavy metals (dissolved and adsorbed to suspended material) is reported. Every year, the 90 percentiles are determined for the individual monitoring sites. A 90 percentile is the concentration level that is exceeded in 10% of the measurements. The graph shows, for each river basin, the average 90 percentile indexed for the MAC or the desired quality standard (negligible risk). Regionally managed waters and nationally managed waters are therefore shown after aggregation.

References

• CIW (2004). Water in Beeld, Water in Cijfers; Voortgangsrapportage over het Waterbeheer in Nederland. Commissie Integraal Waterbeheer, The Hague. http://www.waterinbeeld.nl/wib2004

Relevant sections and indicators in the Environmental Data Compendium

• Surface water quality: Policy
• Heavy metals in rivers
• Eutrophying substances in fresh surface water in the Netherlands, 1985-2001
• Emissions into water in the Netherlands, 1990-2001
• Discharges into water and burden on surface water in the Netherlands, 1990, 1995, 1999 and 2000
• PCB and mercury in eels in the Netherlands, 1980-2000

Relevant information outside of the Environmental Data Compendium

• More information about the monitoring of nationally managed waters.