Metal extraction and processing has caused serious environmental problems. Improper metal mining has not only affected landscape structures but also caused contamination for natural elements. Regarding to soil and water contamination, acid rock drainage from waste rock when operating is the most typical phenomenon.
In spite of the fact that the character of waste rock differs with the kind of ore, many waste rocks contain sulfide minerals related with metals, for example, lead, zinc, copper, silver, or cadmium. A significant sulfide mineral that can often be found in waste rock is pyrite, iron sulfide. When pyrite is presented to air and water, it experiences a chemical response called "oxidation." The oxidation process produces acidic conditions that can hinder plant development at the surface of a waste pile. Bare, non-vegetated, orange-colored surface materials make some waste rock areas easily observable, and they are the most apparent consequence of these acidic conditions.
In case that water infiltrates into pyrite-loaded waste rock, the subsequent oxidation can acidify the water, empowering it to break up metals, for example, copper, zinc, and silver. This generation of acidic water, is generally mentioned to as "acid rock drainage." If acid rock drainage isn't kept from happening, and in the event that it is left uncontrolled, the subsequent acidic and metal-bearing water may deplete into and taint streams or move into the nearby groundwater. The acidity of polluted groundwater may get neutralized since it moves through soils and rocks. In any case, huge degrees of dissolved constituents can remain, hindering its utilization for drinking water or irrigation.
Where acid rock drainage happens, the dissolution and resulting mobilization of metals into surface and groundwater is presumably the most considerable natural effect related with metallic sulfide mineral mining. Acidic and metal-bearing groundwater happens in relinquished underground mine operations and deeper surface excavations that experience the groundwater of a mineralized region. Since they are typically situated at or underneath the water table, underground mines serve as a sort of well which continues loading up with water. Since these waters move through underground mine workings before releasing, they collaborate with the minerals and rocks exposed in the mine. In the event that sulfide minerals are available in these rocks, particularly pyrite, the sulfides can oxidize and cause acid rock drainage.