What is Acid Rain?
Acid rain refers to any form of precipitation (rain, snow, fog, hail, or dust) that is unusually acidic, meaning it has elevated levels of hydrogen ions (low pH). It is primarily caused by industrial emissions of sulfur dioxide and nitrogen oxides, which react with water, oxygen, and other chemicals in the atmosphere to form sulfuric and nitric acids.
How Does Acid Rain Form?
The primary precursors of acid rain are sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) released into the atmosphere. These gases predominantly come from burning fossil fuels in power plants, factories, and vehicles. Once in the atmosphere, these gases can travel long distances and react with water, oxygen, and other substances to form acidic compounds, which then fall to Earth as wet or dry deposition.
Sources of Acid Rain Pollutants
While natural sources like volcanic eruptions and decaying vegetation contribute small amounts, human activities are the dominant cause. The largest sources of SO₂ and NOₓ emissions are electricity generation (especially from coal-fired power plants), industrial facilities, and vehicle exhaust. These emissions are carried by wind currents and can affect areas far from the original source.
Impacts of Acid Rain
Acid rain has devastating effects on the environment. It acidifies lakes and streams, harming aquatic life; damages trees and forest soils by leaching essential nutrients and releasing toxic aluminum; corrodes buildings, statues, and historical monuments; and can contribute to respiratory problems in humans. It disrupts ecological balance and reduces biodiversity in affected areas.