Cadmium and zinc interactions in trace element accumulation in chamomile

In many contamination situations, various heavy metals act simultaneously and may interact; the present study examines the effects of cadmium (Cd) and zinc (Zn), two chemically similar elements, on trace-element accumulation under different environmental conditions. Chamomile (Matricaria recutita L.) was grown in pot experiments with increasing additions of Cd, Zn, or a combination of both metals to the substrate. The plants were tested on a sandy soil and a humus garden soil. The experiment was performed twice, in summer and in autumn. Because the Cd concentrations reached up to 19.3 mg kg(-1) when the Cd supply in the soil was 3 mg kg(-1), chamomile can be characterized as a plant accumulating this heavy metal. More Cd was taken up from the sandy soil than from the humus garden soil, whereas the Zn contents were higher in the plants grown in summer on the garden soil. The addition of Zn to the soils led to a suppressed Cd accumulation into the above-ground plant parts. A further increase in the Zn supply, however, did not afford a further decrease in the Cd levels in the plants. On the other hand, the Cd supply did not influence the Zn accumulation. Thus an appropriate Zn supply to the plants can reduce, but cannot prevent totally, Cd accumulation in chamomile to meet the limits imposed for a pharmaceutical use of this plant. The copper (Cu) and manganese (Mn) contents were little influenced by the Cd and Zn additions to the soils.