Acid drainage does not normally occur in areas before mines are built but tends to happen after the mine has been in operation for many years. what causes acid drainage?
a. concentrated acids used to dissolve metals from the rock are picked up in rainwater.
b. mining exposes unweathered rock surfaces that react with water and the atmosphere to generate acids.
c. the acid is already present in trapped underground pockets and is released by mining equipment.
d. abandoned mining equipment leaks acids from batteries.

Mining exposes unweathered rock surfaces that react with water and the atmosphere to generate acids.

The large amount of freshly exposed rock provides the sulfur to generate sulfuric acid

most community's take hundreds of years to become stable

thrombocytopenia, which is a deficiency in blood platelets, can cause bleeding and bruising in the dermis similar to senile purpura. other possible causes include: exposure to ultraviolet rays and aging skin are common causes of senile purpura. senile purpura may also be a sign of collagen loss in the skin and bones.