Metal contamination in wildlife living near two zinc smelters

Wildlife in an oak forest on Blue Mountain was studied 10 km upwind (Bake Oven Knob site) and 2 km downwind (Palmerton site) of two zinc smelters in eastern Pennsylvania, USA. Previous studies at sites near these smelters had shown changes in populations of soil microflora, lichens, green plants and litter-inhabiting arthropods. The 02 soil litter horizon at Palmerton was heavily contaminated with Pb (2700 mg kg⁻¹), Zn (24 000 mg kg⁻¹), and Cd (710 mg kg⁻¹), and to a lesser extent with Cu (440 mg kg⁻¹). Various kinds of invertebrates (earthworms, slugs and millipedes) that feed on soil litter or soil organic matter were rare at, or absent from, the Palmerton site. Those collected at Bake Oven Knob tended to have much higher concentrations of metals than did other invertebrates. Frogs, toads and salamanders were very rare at, or absent from, the Palmerton site, but were present at Bake Oven Knob and at other sites on Blue Mountain farther from the smelters. Metal concentrations (dry wt) in different organisms from Palmerton were compared. Concentrations of Pb were highest in shrews (110 mg kg⁻¹), followed by songbirds (56 mg kg⁻¹), leaves (21 mg kg⁻¹), mice (17 mg kg⁻¹), carrion insects (14 mg kg⁻¹), berries (4·0 mg kg⁻¹), moths (4·3 mg kg⁻¹) and fungi (3·7 mg kg⁻¹). Concentrations of Cd, in contrast, were highest in carrion insects (25 mg kg⁻¹), followed by fungi (9·8 mg kg⁻¹), leaves (8·1 mg kg⁻¹), shrews (7·3 mg kg⁻¹), moths (4·9 mg kg⁻¹), mice (2·6 mg kg⁻¹), songbirds (2·5 mg kg⁻¹) and berries (1·2 mg kg⁻¹).

Concentrations of Zn and Cu tended to be highest in the same organisms that had the highest concentrations of Cd. Only a small proportion of the metals in the soil became incorporated into plant foliage, and much of the metal contamination detected in the biota probably came from aerial deposition. The mice from both sites seemed to be healthy. Shrews had higher concentrations of metals than did mice, and one shrew showed evidence of Pb poisoning; its red blood cell ALAD activity was greatly reduced, one kidney contained acid-fast intranuclear inclusion bodies, and the other kidney had 280 mg kg⁻¹ Pb (wet wt). The livers from two cuckoos from Palmerton had elevated Pb concentrations (18 and 25 mg kg⁻¹, wet wt). Most of the songbirds seemed to be healthy.