Acid rain occurs when sulfur dioxide (SO2) and nitrogen oxides (NOx) react in the atmosphere with water. When the mix condenses and returns to earth, it comes in the form of polluted rain, fog, or snow. The contaminated precipitation also causes the weakening of infrastructure such as corrosion of steel structures such as bridges, and weathering of stone buildings and statues. It can also have a number of adverse effects on natural ecosystems by disrupting sensitive equilibriums.
