Will summarised the past importance of metal mining in the UK. Because these mines are now abandoned there is a pollution problem affecting ground and surface water. Although there has been some recent mining for gold and fluorspar, the present government legislation requiring the total cleaning up of all pollution is a disincentive.
The legacy of past mining includes tourism, the conservation of historical monuments and also of specialist metallophile plants, and effects on the physical landscape.
The weathering of metal ores by air, water and bacteria generally produces acid water containing toxic metals although in limestone areas the water may be neutralised. The oxidation of pyrite produces red iron oxide colouring streams a rich orange. All this is inimical to freshwater life. In extreme cases of pollution, e.g. Cadmium in Japan and Arsenic in Cornwall, humans may be directly affected.
The EU Water Framework Directive targets rivers and aquifers and the UK government was obliged to follow this after the closure of coal mines and their subsequent flooding. Metal mines were worked by small enterprises out of government control. However the National Assessment of Rivers found 6% of these were affected by metal pollution and more than 300 pollution sources have been identified. Treatment options can be chemical e.g. using CaO which is costly, “passive” e.g. reed beds and sulphate reducing bacteria. Bioreactors containing sewage sludge, whelk shells and compost have been tested in the lab with promising results.