Using Collembola to assess the risks of applying metal-rich sewage sludge to agricultural land in western Scotland

The recent United Kingdom ban on the disposal of sewage sludge at sea has led to the prediction that land application of sludge will become more widespread. The positive aspect of recycling nutrients may, however, be offset by the risk of contamination by heavy metals that are frequently present in sludge. The environmental impact of applying metal-rich sewage sludge to agricultural land was, therefore, assessed using Collembola. A combination of pitfall trapping and suction sampling was used to monitor epigeal/hemiedaphic Collembola on a small plot field trial in the west of Scotland. Four sludge treatments were investigated: cadmium-rich sludge, zinc-rich sludge, uncontaminated sludge and a no-sludge control. It was found that the abundance of Lepidocyrtus cyaneus Tullberg and Isotoma viridis Bourlet was significantly lower in plots receiving cadmium-rich sludge than those receiving uncontaminated sludge. Isotoma anglicana Lubbock was not influenced by the presence of metals in sludge and Isotomurus palustris (Muller) was actually favoured by the application of metal-rich sludge. Other aspects of collembolan ecology, and the efficiency of the two sampling methods, are also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.