With climate change at the top of the news, and government agendas, other equally important matters on the resources of the Earth are often overlooked. There are greater ‘monstrosities’ brought about as a result of anthropogenic activity, and one of those at the forefront of environmental scientists’ minds is that of acid mine drainage.
Acid mine drainage occurs as a result of the weathering of sulphide minerals such as pyrite. These minerals react with both oxygen and water, resulting in increased acidity of waters by developing H+ ions. Although this can occur naturally through the weathering process, the rate at which it occurs rapidly increases when these minerals become exposed by mining practices. Waters are measured to have a low pH of 1-3 (whereas ‘normal’ waters would be between pH 5-7) due to the oxidation of iron-sulfide (although this can occur with a number of sulphides), causing them to become orange in colour. There are numerous examples worldwide of sites affected by AMD including Parys Mountain (Wales), Avoca (Ireland) and Summitville Mine (Colorado) to name a few.
‘The Copper Mountain’ – Parys Mountain, Anglesey, Wales.
An example of AMD with iron precipitates draining from Parys Mountain.
The main problem with acid mine drainage is that it still occurs years after the closure of the mine – the chemical processes initiated by the mining continue. The acidic waters of the sites then drain into adits, and eventually freshwater rivers leading to the sea, causing pollution on a much greater scale. AMD can also result in the formation of ochre – a clayey material containing ferric oxide – this material smothers the river bed, killing riverine and marine life.
Draining waters from the Avoca mine, polluted as a result of AMD.
The question is, can we do anything to help? Is there a method of remediation which we could apply? Have there been successes, and if not, why not?
That we shall investigate at a later date, but feel free to leave your suggestions in the comments below, or share any information/photographs you have with regards to acid mine drainage. Although our aim is to add to your knowledge, we like to improve our own a bit too!
Water of the World