Impacts of acid rain at Higher Level: The same statement as SL, with different real cases: red spruce in the Appalachians, the Adirondack lakes, the Acropolis, the Huai River and the OECD's forecast. At HL, put a price on the damage: who pays for the healthcare, the lost harvests and the repairs, and who caused them.
Practise this as you read
- Explain impacts on soils, lakes, buildings and lungs.
- Explain how they become economic losses.
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Soils and forests: On land, acid rain harms plants twice: directly, through their leaves, and indirectly, by changing the soil they grow in.
Acid rain on land
- Leaching: acid washes nutrients (calcium, magnesium, potassium) out of the soil, so it is less fertile.
- Toxification: acid releases aluminium and other metals from soil particles; they damage roots.
- Soil organisms and decomposers are harmed, so dead matter rots slowly and nutrients cycle slowly.
- Direct damage to leaves: acid strips the waxy cuticle; needles yellow and fall; less photosynthesis.
- Weakened trees die from frost, drought, pests and disease (forest dieback); lichens die first.
- Fewer plants mean less food for herbivores, more soil erosion and lower crop yields.
Remember it as: Leaves burnt, soil robbed, roots poisoned.
Real example: in the Appalachian mountains of the eastern USA, acid rain leached calcium from the soil and from the needles of red spruce. Without it the needles froze in winter, and many trees died.
Link the acid to the harm: 'Acid deposition' alone, or 'trees die' alone, is not enough. Say how: acid leaches nutrients, so trees grow less.
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Most acid that falls on a forest ends up in its streams and lakes, carrying aluminium from the soil with it.
Acid rain in lakes and rivers
- Acid run-off and snowmelt lower the pH of lakes and rivers.
- Acid soils release aluminium, which washes into the water and becomes toxic there.
- Aluminium damages fish gills: they clog with mucus, so less oxygen is taken in.
- Snails, crayfish and mayflies cannot build shells and exoskeletons in acid water; eggs fail.
- Sensitive species die out first; acid-tolerant ones (some mosses, midges) increase.
- Food webs get shorter, biodiversity and productivity fall; extra nitrate can over-fertilise.
Rain
- Acid rain from Midwest coal power stations fell on New York's mountains
Soil
- Thin, calcium-poor soils released aluminium into the streams
Lakes
- Many Adirondack lakes fell below pH 5
Fish
- 1984-87 survey: 346 of 1,469 lakes, about 24%, had no fish at all
Shells and gills: Two words to use: aluminium damages fish gills; acid water stops invertebrates building shells and exoskeletons.
Stone and metal: Acid deposition corrodes the materials cities are built from, above all stone made of calcium carbonate.
Buildings and materials
- Marble and limestone are calcium carbonate: acid dissolves them.
- The reaction makes gypsum, which traps soot as a black crust, then flakes off.
- Carved detail, inscriptions and statues are slowly worn away.
- Acid corrodes steel and iron (rust), bronze and copper, and paint.
- Repairs, cleaning and replacing stone and metal cost money.
Real example: the six marble Caryatids were being eaten away by Athens' polluted air. In 1979 they were moved indoors to a museum, and copies now stand in their place.
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Before it falls as rain, the acid is already in the air we breathe, as tiny particles.
Acid in the air we breathe
- SO₂ and NOₓ form tiny sulfate and nitrate particles: part of PM2.5.
- PM2.5 reaches deep into the lungs: tissue damage and lung inflammation.
- It causes coughing, asthma attacks, bronchitis and reduced lung function.
- The finest particles enter the blood: more heart disease and early deaths.
- Acid fog and SO₂ irritate the eyes and airways directly.
- Children, older people and those already ill suffer most.
Sulfate and nitrate particles
- Formed from SO₂ and NOₓ
- Part of PM2.5
- Deep in the lungs, into the blood
- Inflammation, asthma, heart disease
Acid gases and fog
- SO₂, NOₓ, acid droplets
- Breathed in near the source
- Irritate eyes, nose, throat
- Coughing, wheezing
Real example: in China, homes north of the Huai River burned coal for heat. Their air had about 46% more particles than just south of the river, and people lived about three years less.
Pollution costs money: Every impact on ecosystems, people and buildings has a price, paid by health services, businesses and governments.
The economic cost
- Disease raises healthcare costs.
- Sick workers mean lost workdays and lower productivity; early deaths shrink the workforce.
- Lower crop, timber and fish yields raise food prices and cost jobs.
- Repairs to buildings, monuments, bridges and equipment.
- Paying for clean-up technology, monitoring and education campaigns.
- Tourists stay away and property values fall in polluted places.
Polluted air costs
- Hospital visits, early deaths
- Lost workdays
- Smaller harvests, dead fish
- Corroded monuments
Cleaner air brings
- Less asthma, sore eyes, heart disease
- Lower health costs, longer lives
- Healthier plants, more species
- Clearer views, cleaner buildings
Real example: in 2016 the OECD warned that by 2060 outdoor air pollution could cost about 1% of the world's GDP every year, through lost workdays, health spending and smaller harvests.
One cost per point: Name the impact AND the cost it causes: 'asthma raises healthcare costs', not just 'health'. 'Improved health' alone is not enough either.
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How this comes up: Paper 2: a Section B (b) on the economic losses that air pollution causes, and short Section A parts on one or two impacts.
Lahore, in Pakistan, is often covered in smog from traffic, brick kilns and coal-burning industry.
Explain how urban air pollution could lead to significant economic losses.
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A Section A part asks for two impacts on living things.
Nitrogen oxides from a busy motorway also contribute to acid deposition.
Outline two impacts of acid deposition on living systems.
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