Verhalten von Kupfer, Zink und Cadmium in einem stark belasteten Kalkboden

Abstract

Near a brass foundry, the soil is severely polluted by the heavy metals cadmium, copper, and zinc which have been emitted for more than 80 years. Lime and clay present in the soil result in high pH and high adsorption capacity, leading to a small mobility of the metals. Therefore, the heavy-metal pollution is localized in the upper 25 cm of the soil. The enrichment of the metals in the topsoil substantially decreases biological decomposition rate and breakdown of the litter. The fertility of the soil is disturbed and the meagre vegetation on the site is strongly polluted.The three metals differ in their binding forms and their mobility. Cadmium is particularly adsorbed in the diffuse layer of the cation exchanger or associated with carbonates, which results in a relatively high plant availability. On the other hand, the exchangeable amounts of copper and zinc are small. Main binding forms of these metals are association with carbonates or iron oxides and especially in the case of copper the complexation by humic substances. In the soil solution, hydrated ions are the main species of cadmium and zinc, whereas copper is almost exclusively complexed by dissolved organic matter (DOC). As hydrated ions are preferentially taken up by plants, the availability of cadmium and zinc is greater than that of copper.