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

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The Froghall copper works have been operational since 1890 and produce copper and copper-alloy products. Some previous reports suggest that these works have been a source of environmental contamination. The present study investigates the impact of the Froghall works on its surroundings in terms of cadmium, copper and zinc contamination of surface soils. Results show that these soils are contaminated with cadmium and copper but zinc levels are within normal background concentrations for uncontaminated soils. Water-extractions of soils show that cadmium is about three times more readily available than copper. However, the presence of chelating agents in soils can render both the elements much more bioavailable. Sequential extractions of representative contaminated soils show that although copper in each sample is mainly associated with the soil organic phase and therefore may be non-bioavailable to a large extent, association of cadmium in the different soil samples is variable. Mean values for cadmium suggest that even though a high percentage of cadmium is associated with the residual fraction of soils, the rest of it is highly exchangeable and so bioavailable. Overall, it is suggested that the soils around the Froghall works have a higher potential of toxicity to plants from cadmium than copper. Direct soil ingestion in the contaminated areas by grazing livestock could be a source of cadmium and copper into the food chain and it is suggested that further investigation and even clean up of some sites may be required before allowing the animals to graze freely on such land.