Acid deposition

Acid Deposition Overview

• Acid deposition, also known as acid rain, is a broad term referring to the deposition of acidic components in rain, snow, fog, or dry particles.
• Caused primarily by human activities, particularly the burning of fossil fuels and industrial emissions that release sulphur dioxide (SO2) and nitrogen oxides (NOx) into the atmosphere.
• These gases react with water, oxygen, and other substances to form sulphuric acid and nitric acid.

Process of Acid Deposition

• Sulphur dioxide and nitrogen oxides in the atmosphere undergo chemical transformations, usually catalysed by sunlight, to form sulphuric acid and nitric acid.
• These acid particles then combine with water vapour in the atmosphere to form acid rain.
• This acid rain returns to Earth’s surface via precipitation, affecting both natural environments and human-made infrastructure.

Impacts of Acid Deposition

• Acid deposition can damage vegetation - altering nutrient balances in soils, making trees and plants more vulnerable to environmental stress factors.
• It affects aquatic ecosystems by making water bodies too acidic, disrupting the balance of species.
• It poses serious consequences for built environments, most notably the corrosion of buildings, particularly those constructed from limestone and marble.

Possible Mitigation Measures

• Reduction in the use of fossil fuels, promoting energy efficiency and the use of renewable energy resources.
• Implementation of cleaner industrial processes and flue-gas desulphurisation – using alkaline sorbents to reduce SO2 emissions.
• Regulation and enactment of emission standards on a local, national and global level to bring about substantial cuts in SO2 and NOx emissions.