Concentrations of Cd and Zn were monitored in the Keersop
stream on amonthly basis from1980 to 2000 and for Cd varied between 0.12 and 2 μg/l, while Zn concentrations varied
between 10 and 440 μg/l. In comparison, the Dutch water
quality threshold value is 0.4 μg/l (dissolved) or 2 μg/l (total,
dissolved plus suspended) for Cd, and 9.4 μg/l (dissolved) or
40 μg/l (total) for Zn (http://www.rivm.nl/rvs/), which is
similar to the EU maximum allowable concentration of up to
1.5 μg/l Cd depending on water hardness classes (EU, 2008).
The dissolved concentrations of Cd and Zn in the Keersop are
related to groundwater levels and stream discharge rates
(Kroes et al., 2008a) because Cd and Zn have accumulated in the
topsoil. Therefore, the impact of climate change on groundwater
levels and discharge rates is expected to impact the
concentrations of Cd and Zn in the Keersop as well.