Final answer:
Sulfuric acid (H2SO4) initiates the formation of acid mine drainage from improperly disposed pyrite, leading to environmental contamination through the mobilization of heavy metals.
Step-by-step explanation:
The chemical that initiates the formation of acid mine drainage when pyrite (iron sulfide) is not disposed of properly is sulfuric acid (H2SO4). Upon exposure to water and oxygen, pyrite oxidizes and forms sulfuric acid, which can then mobilize other heavy metals present, leading to environmental contamination.
This process begins with the production of sulfur dioxide (SO2) and sulfates (SO42-), which in the presence of water become sulfuric acid. To mitigate this issue, industries often employ measures such as SO2 scrubbers, using compounds like lime to neutralize sulfuric acid before it can cause harm.