Acid Deposition

Question 1

What is acid deposition?

Answer 1

Acid deposition is the general term for acid coming down from the air

Wet deposition = acid comes down in form of rain (or snow)

Dry deposition = when acid comes down as ash or dry particles

Question 2

What is the pH of normal unpolluted rain?

Answer 2

• Normal unpolluted rain is slightly acidic + has a pH of 5.6, caused by presence of co2 in atmosphere
• Precipitation is called acidic when its pH is well below pH 5.6

Question 3

What are the main primary pollutants leading to acid deposition?

Answer 3

• sulphur dioxide
• nitrogen oxides

They react with water to form strong acids (sulphuric and nitric acids)

Question 4

How are sulphur dioxide + nitrogen oxides produced naturally?

Answer 4

Sulphur dioxide by volcanic eruptions

Nitrogen oxides by lightning

Question 5

How does burning fossil fuels lead to formation of primary air pollutants?

Answer 5

• Sulphur dioxide formed when sulphur-containing fuels (e.g. coal, oil) are combusted
• Nitrogen oxides formed by reaction of oxygen + nitrogen from the air, that takes place at high temp. during fossil fuel combustion

Question 6

What are the effects of acid deposition?

Answer 6

• weakening tree growth in coniferous forests
• decreasing pH of water bodies, affecting aquatic organisms
• toxic effects eg. increased solubility of metal ions like aluminium (toxic to fish+plant roots)
• nutrient effects eg. leaching of nutrients

Question 7

3 effects of acid deposition on coniferous forests

Answer 7

• Leaves + buds lose chlorophyll
• This reduces growth +allows nutrients to be leached out and pathogens to gain entry
• Symbiotic root microbes killed, reducing availability of nutrients

Question 8

Toxic effects of acid deposition // aluminium ions - effect on fish and other aquatic organisms

Answer 8

• Decreased pH of soil makes aluminium more soluble
• Aluminium ends up in streams + rivers
• aluminium disturbs fish’s ability to regulate amount of salt in body, so salt content is slowly lost + fish die

Question 9

Toxic effects of acid deposition // buildings

Answer 9

Limestone buildings + statues (w great archaeological + historical value) react w acid and dissolve

Question 10

Toxic effects of acid deposition // peat bogs

Answer 10

• peat bogs affected by acid rain produce up to 40% less methane than before
• because bacteria that use sulphates as a food source outcompete the ones that use methane

Question 11

Toxic effects of acid deposition // human health

Answer 11

• dry deposition in form of small particles of sulphates + nitrates penetrate into our lungs
• premature deaths from lung disease, asthma, bronchitis

Question 12

Why are the effects of acid deposition regional in contrast to climate change // ozone depletion that affect all the Earth?

Answer 12

• Before the pollutants can spread over long distances, they return to the surface as dry or wet precipitation
• The acids seldom travel further than a few thousand kilometres

Question 13

Where does dry deposition usually occur?

Answer 13

• occurs quite close to source of acidic substances

- consists of sulphur dioxide, sulphur trioxide + nitrogen oxides

Question 14

Where does wet deposition usually occur?

Answer 14

• occurs at slightly longer distances from the sources of primary pollutants
• consists of sulphurous acid, sulphuric acid + nitric acid

Question 15

It is mainly the downwind areas of major industrial regions that are strongly affected. Give 2 examples of this

Answer 15

• Scandinavian forests + lakes affected by acid rain originating in UK, Poland + Germany brought over by prevailing southwestern winds
• Industrial pollution from USA is blow by prevailing winds towards Canadian forests

Question 16

Why does the impact of acid rain depend on the geology of the area on which it falls?

Answer 16

• Acid rain does little harm to limestone and chalk soils as they are alkaline soils + neutralise the acids
• But acid rocks produce soils that are v sensitive to acid rain

Question 17

Pollution management strategies for acid deposition // altering human activity producing pollution ACTION

Answer 17

• replace fossil fuel use w ethanol for cars + renewable energy sources
• reduce overall demand fr electricity - education campaigns to turn off lights etc
• use less private transport

Question 18

Pollution management strategies for acid deposition // altering human activity producing pollution (EVALUATION)

Answer 18

• we live in a fossil fuel reliant economy

- demand for power is every increasing, esp. in India + China as they industrialise

Question 19

Pollution management strategies for acid deposition // regulating + reducing pollutants at point of emission (ACTIONS)

Answer 19

• Clean-up technologies at end of pipe locations e.g. scrubbing in chimneys to remove sulphur dioxide
• Catalytic converters convert nitrous oxides back to nitrogen gas

Question 20

Pollution management strategies for acid deposition // regulating + reducing pollutants at point of emission (EVALUATION)

Answer 20

• Clean-up technologies are expensive + costs passed onto consumer
• Catalysers are cost effective if well maintained, but expensive to buy

Question 21

Pollution management strategies for acid deposition // clean up and restoration

Answer 21

• liming acidified lakes (effective but expensive)
• recolonise damaged areas
• liming forestry plantations // trees acidify soils as they remove nutrients
• international agreements (difficult to establish + monitor)

Question 22

What happened in 1999 in Europe?

Answer 22

27 countries signed up to new protocol on Long Range Transboundary Air Pollution to reduce + prevent air pollution

Question 23

Evaluation of international agreement success in Europe

Answer 23

• avg of 50% reductions achieved by 2000
• but LEDCs rapidly industrialising + emissions set to increase unless MEDCs can help them to leapfrog to clean technologies
• due to regional character of acid deposition, international agreements are more regional
• but Kyoto Agreement will also help reduce acid deposition

Question 24

Reducing effects of acid deposition // Liming lakes to neutralise acidity

Answer 24

> From 1950s, loss of many fish + invertebrate species in Scandinavian lakes linked to high levels of lake acidity
By 1990, 400+ lakes virtually lifeless
In 1980s, Sweden added limestone to lakes + rivers w mixed results
pH of treated lakes quickly raised but short-lived because of acidic nature of inflow of water
lime affected nutrient balance

Question 25

Reducing effects of acid deposition // pre combustion techniques

Answer 25

- reduce sulphur dioxide emissions by removing sulphur from fuel before combustion - sulphur obtained can be used in construction (as gypsum) or as the element sulphur in the chemical industry