Heavy metal contamination of soils in a mining area in South Africa and its impact on some biotic systems

In soils, animals and plants from selected sites in the Rustenburg mining area, a part of the South African ore belt, the heavy metal burden was examined. These sites belong to different soil types and are characterized by different land-use (agriculture, grassland). The heavy metal contamination of the soil samples is relatively high and is dominated by chromium and nickel, metals, which are extracted in the mine near the sampling sites. These high heavy metal concentrations had no clear inhibitory influence on micro-organisms or the enzyme activity of soils. It appears that the high clay content of the soils may counteract the influence of heavy metals. On the other hand, tolerant microbial populations may have been established. In addition, the investigated culture plants there was no correlation between the heavy metal content of the soils and the concentrations in roots and shoots. The dangerous, potential contamination of organs in humans seems to be modest, with the exception of tobacco leaves. The heavy metal content of tissues in the examined animals reflect the environmental habitat in situ with no obvious influence on the health of the animals.