Distribution and bioavailability of metals in soils in the vicinity of a copper works in Staffordshire, UK

The Froghall copper works have been operational since 1890 and produce copp er and copper-alloy products. Some previous reports suggest that these work s have been a source of environmental contamination. The present study inve stigates the impact of the Froghall works on its surroundings in terms of c admium, copper and zinc contamination of surface soils. Results show that t hese soils are contaminated with cadmium and copper but zinc levels are wit hin normal background concentrations for uncontaminated soils. Water-extrac tions of soils show that cadmium is about three times more readily availabl e than copper. However, the presence of chelating agents in soils can rende r both the elements much more bioavailable. Sequential extractions of repre sentative contaminated soils show that although copper in each sample is ma inly associated with the soil organic phase and therefore may be non-bioava ilable to a large extent, association of cadmium in the different soil samp les is variable. Mean values for cadmium suggest that even though a high pe rcentage of cadmium is associated with the residual fraction of soils, the rest of it is highly exchangeable and so bioavailable. Overall, it is sugge sted that the soils around the Froghall works have a higher potential of to xicity to plants from cadmium than copper. Direct soil ingestion in the con taminated areas by grazing livestock could be a source of cadmium and coppe r into the food chain and it is suggested that further investigation and ev en clean up of some sites may be required before allowing the animals to gr aze freely on such land.