From 1880 to 1974 the chimneys of four zinc ore smelters,
using very polluting pyrometallurgic zinc refining procedures,
emitted oxides of heavy metals that reached the soils in the
Kempen area either by dry deposition or through rainfall.
Besides the atmospheric emissions, heavymetals contaminated
the area through zinc ash roads, severe groundwater pollution
at the smelter sites and direct drainage fromthe smelter sites to
surface water. While the zinc ash roads and the smelter sites
caused intense line and point source contamination, the historic
input of heavy metals on the soil through atmospheric
deposition has resulted in an excessive accumulation in the
topsoil in the Kempen region. The zinc ore smelters switched to
an electrolytic process in 1974, but despite the cessation of
direct emissions to the environment, soils and sediments still
contain highmetal concentrations and act as possible sources of
metal pollution for the aquatic environment. Cd and Zn
concentrations in the soil range from b0.2 mg/kg Cd and
b20 mg/kg Zn at locations over 30 km from the smelters to
5.3 mg/kg Cd and 733 mg/kg Zn at a location within two km
from the Budel smelter (Van der Grift and Griffioen, 2008).
Because the accumulation of Cd and Zn is so widespread,
leaching to the groundwater and surfacewater threatenswater
quality in the entireKempen area.DeJonge et al. (2008) showed
that the zinc concentrations in the Dommel, a small lowland
river in this area, have impacted the macro-invertebrate
community composition and diatom community structure.