Metal pollution in a salt marsh and its effect on sheep.

In a salt marsh in the Westerschelde, samples were taken from soil and vegetation during 15 months. Concentrations of Cd, Pb, Cu, Zn, Mn, and Fe were measured and compared with levels of these metals in livers, kidneys, and faeces of sheep grazing there. The contamination extent of soil ranges from 2 (Cu) to 8 (Cd); in spring some plants exceed the advised maximum tolerable level of dietary Cd for sheep. However, levels of metals in organs from sheep do not indicate intoxication, nor did clinical inspections and autopsies. It is suggested that sheep exhibit a selective consumption behaviour and that the bioavailability of the metals in this marsh is low.