Aerial view of ash pond near Turek, Poland. Former open pit coal mine now used to store coal ash after burning in power plants. The ash is mixed with water and pumped through a pipeline into the ash pond. The vivid green colour indicates the presence of calcium carbonate used to neutralise the acidic wastewater. Although this site is nicknamed 'The Polish Maldives', the attractive-looking water is actually toxic wate. Ash ponds can contaminate the environment with pollutants harmful to human health.