How does acid rain affect the corrosion of the Statue of Liberty?

Statue of libery is made from copper (Cu). Copper reacts when acid rain (2H+ + SO42-) falls forming copper sulfide (CuS, but other types of sulfides also possible). CuS oxidises slowly to copper sulfate (CuSO4) which has green colour. So, the statue of liberty has changed its colour from black (or copperish) to green.