Ecological impact of 100 years of metal processing at Prescot, northwest England

Abstract

The environmental legacy of 100 years of a metal processing industry is evaluated, based on a case study of ecotoxicological research that has been carried out in the area surrounding a copper refinery, a cadmium alloying plant, and a brass foundry at Prescot, northwest England. Aerial fallout of particulate copper and cadmium has been very localized, but soluble and potentially more toxic forms of the metals have been transported further. Accumulation of Cu and Cd in soils to exceptionally high levels has occurred, with Zn and Pb also highly elevated, but depth profiles, spatial dispersion patterns, mobility, and speciation vary between metals. A very limited effect on tree growth is apparent, although phytotoxic symptoms are readily observed in tree seedlings. Site contamination is reflected in metal concentrations in tree rings. Significant food chain transfer of Cu and Cd to invertebrates and small mammals has occurred, affecting population sizes of invertebrates and producing toxicological symptoms in shrews. Copper may have been a cause of concern for livestock in surrounding rural areas and human ingestion of metals may have been significant in the past, but currently both are likely to be negligible. Impingent metals have led to selection for metal resistance in some plant species; metal tolerance traits in grasses appeared rapidly in lawns in the area and the intensity of tolerance in plants directly reflects the localized degree of contamination. Cellular metal tolerance traits have been induced in trees as an acclimation response to metal contamination. Declining industrial activity in recent years has resulted in unexpected pulses of plant-available soil Cd and of several other metals including Mn, Ca, Mg, and Ni. Metal disappearance rates from surface horizons are also higher than expected following recent cessation of metal processing, and the fate of these transitory metals presents further cause for concern.Key words: heavy metals, ecosystem, food chains, pollution, metal tolerance.