Studies on environmental pollution in a given region often suffer
from the lack of reliable information on the natural level of trace
elements. The natural contribution to the trace element contents
and fluxes of local and regional ecosystems strongly depends on the
local composition of the lithosphere, i.e. the dominating rock type.
The dispersion of trace elements in the different environmental compartments
is mainly governed by weathering and mass transport. Based on examples
from Central Europe, this paper gives an insight into the typical
natural input of six major, geochemically defined rock types (?natural
background?). It also presents two cases of regional ?natural contamination?
related to ore deposits. Each rock type contributes in a characteristic
manner to the major and trace element budget of soils, sediments,
plants, surface and ground waters. Whereas well soluble elements
such as Ca, Sr, Mg, Na and K are enriched in the water phase, less
soluble elements such as Al, Fe and in part Si and most trace elements
are enriched in the soil compartment. In the latter, these elements
are either part of, or are adsorbed on organic material, oxy-hydroxides
or clay type minerals. From soils, trace elements are transported
either to plants or to ground waters. The extent and manner to which
chemical elements of the underlying rocks are dispersed in their
surroundings depends first of all on the chemical composition of
the parent material, varying greatly from one rock type to the other.
Secondly, the typical pH created in the soil and water compartments
strongly influences the sorption behavior and thus retention or release
of specific elements. Soils formed on silicate rocks usually exhibit
acid conditions (pH 4?6.5), related soil and ground waters typically
are near neutral (pH 6.5?7.5). However, soils and waters related
to carbonate rock environments are usually neutral to alkaline (pH
7?8.5). Soils on granitic silicate rocks have been found to be slightly
enriched in Zr, Ti, Pb and Rb and often host ore deposits rich in
U or As, which influence the water and sediment composition of whole
catchment areas. Basaltic silicate rocks enrich the soils typically
in Sr, Ti, Fe, V, Cr, Ni, Cu and Zn in concentrations up to three
times those of granites. Mg-rich silicate rocks, such as peridotites
and serpentinites, typically enrich soils, plants and waters with
very high amounts of Mg, Fe, Cr, Co, Ni and V, but other trace elements
remain very low. Al-rich silicate rocks, such as shales and micaschists,
are often rich in sulfur and metal traces such as Zn, Pb, As and
Cd. In contrast, carbonate dominated rocks, such as limestones or
sulfate bearing dolomites, typically contribute to enrich their environment
with Mn, F, S, Cl, Ba, Sr, As, Cd and radon. In conclusion, insufficient
knowledge of this natural contribution can lead to misinterpretations
of contaminated sites, especially for elements such as Ni, Cr, Zn,
V, Cd and As.