What is Acid Mine Drainage?

Acid Mine Drainage (AMD) is a significant environmental issue that arises from the mining of coal, precious metals, and other minerals.

Reservoir contaminated by AMD from nearby Tin Mine, La Paz, Bolivia. Photo credit: Jack Prommel

When rocks containing sulfide minerals, such as pyrite (iron sulfide), are exposed to air and water during mining activities, a plethora of chemical reactions ensue. These reactions primarily involve the oxidation of metal sulfides resulting in the release of sulfuric acid and metals into the water stream.

The acidic water can further leach out metals like arsenic, copper, and manganese from surrounding rocks, creating a stream that can severely contaminate groundwater and surface water bodies. This process not only poses a threat to aquatic life but also affects plant health, animal life, and human communities dependent on these water sources.

The management and mitigation of AMD are critical due to its destructive impact on ecosystems and its long-lasting presence in the environment, often continuing to affect areas long after mining operations have ceased.