A comparison of cadmium in ecosystems on metalliferous mine tailings in Wales and Ireland

A comparative study of the concentrations of cadmium in ecosystems developed on tailings from lead/zinc mines was undertaken. Mine soils, vegetation, ground-dwelling invertebrates and Apodemus sylvaticus from nine historic and abandoned mines in Wales and a modern Irish mine site were sampled in order to evaluate and compare exposure risks to wildlife. There were three high soil cadmium sites (155-300 mg kg^-1 ) all from north-east Wales sites, one intermediate site (21 mg kg^-1) the Irish mine tailings, with the other sites having low (background) cadmium levels. The cadmium levels reflected differences in ore minerology and in particular the presence of the zinc ore, sphalerite. The highest plant and invertebrate cadmium levels generally occurred in the three high soil cadmium sites. However, occasional high levels were found in plant and invertebrate samples from one or more of the low cadmium sites. Of particular significance was, despite the relatively high soil cadmium, the very low cadmium concentrations in the plants and invertebrates from the Irish tailings. Evidence of food-chain transfer and even biomagnification in invertebrates did not lead to high cadmium levels in kidneys of A. sylvaticus. Only at one high site were the kidney cadmium residues significantly higher than the reference site.