As the acid drainage moves through the surrounding rocks, it dissolves metals from them and carries them along into the natural drainage system. Almost any metal in the area might be dissolved and swept into the water system, says Godin. In the Yukon, the metals most likely to be found in acid mine drainage are zinc, lead, arsenic, and copper. The acid mine drainage makes the water in the streams themselves more acidic, which means that the metals stay in solution and flow downstream, travelling many kilometres from their sources. The metals will stay in their dissolved form until the water passes through alkaline rock that can reduce the acidity of the water enough to precipitate them out of the solution.
Dissolved metal can do a lot of damage to the inhabitants of the stream.
Metal ions in the water attach themselves to the fish's gills, interfering with respiration. They cause damage to liver and kidneys, and weaken the fish so that they are less fit to grow and reproduce. Besides fish, invertebrates, algae, and every aspect of life in the stream can be affected. In high enough concentrations, the acid-dissolved metals can even endanger larger animals and humans who drink the water. Acid rock drainage is not a new phenomenon, Godin says.