6.4 Acid Deposition

How is acid rain formed?

When sulfur dioxide and nitrogen oxides are released into atmosphere from combustion of fossil fuels

What can form from these gases?

Secondary pollutants, resulting in dry and wet acid depositions l

Where are these primary pollutants from?

• Power plants that burn coal, oil, natural gas with impurities in carbon - SO2

• NOx from vehicle exhausts at high temperature combustion processes

How are secondary pollutants formed?

• Undergo chemical reactions with compounds like oxygen, water vapour

• Lead to sulfuric acid and nitric acid

What is the dry deposition of secondary pollutants?

Sulfuric + nitric acid can combine with ash, forming dry particles

• Dry deposition when particles settle on surfaces, including vegetation, buildings, soil

What is wet deposition of secondary pollutants?

• Sulfuric + nitric acid can dissolve in rainwater/snowflakes, forming acidic precipitation

• Affects surface water and soils

What type of effects can acid deposition have?

Direct and indirect

What are the direct effects of acid deposition?

• Can react with metals and rocks (limestone) damaging buildings and statues

Limestone reacts with sulfuric acid/nitric acid which corroded

• Affects aquatic organisms (lowers pH of water, making it hard for species to reproduce)

• Leaf damage - blocks stomata - prevents gas exchange

• Acid rain damages foliage and inhibits nutrient absorption. Coniferous forests (sensitive to this as shallow root systems, thin bark)

What are the indirect effects of acid deposition?

• Increases solubility of metals like aluminium in water

• High levels of Al ions become toxic of fish, affect respiratory systems, impairing growth → death

• Leaching of nutrients from soil (calcium, magnesium, potassium) - reduces availability for plants → nutrient deficiencies → impact plant growth

What are the geographic and trans boundary impacts of acid deposition?

• Areas downwind of major industrial regions can be affected

• Extends across national boundaries, affecting regions in different countries

What are some methods to reduce acid deposition?

• Cleaner technologies

• Regulations on industrial and transportation emissions

• International cooperation and agreements

• Liming lakes to neutralise acidity

• Scrubbing in chimneys of power stations but reduces efficiency

• Desulfurisation

• Catalytic converters

What are ways to alter human activity fo manage pollution?

• Reduce consumption of fossil fuels

• Encourage use of alternative energy sources like renewable energy can reduce sulfur dioxide + NOx

• International agreements and national governments can promote sustainable practices, support clean technologies, reduce emissions

What are the ways to regulate and monitor pollutant release to manage pollution?

• Government regulations and monitoring systems used to control and reduce release of pollutants

• Coal burning power plants and vehicles are major sources of sulfur dioxide, NOx

• Installing pollution control devices like scrubbers, catalytic converters remove these

What are the clean-up and restoration measures to manage pollution?

• In areas heavily affected by acid deposition, clean up and restoration can mitigate damage caused

• Spreading ground limestone/lime acidified lakes and rivers fan neutralise acidity

• Restoring damaged ecosystems can also be achieved through recolonisation efforts e.g. planting acid-tolerant vegetation

What are the limitations to pollution management?

• Applying ground limestone/recolonising ecosystems can be expensive and challenging at large scale

• Prevention through emission reduction is more effective and sustainable in long term