Learning Unit 10: Acidification

1. Learning Unit 10: Acidification

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3. Learning Outcomes • Explain what acid rain is and how it originates • Explain in which parts of the world acid rain occurs • Briefly discuss the impact of acid rain on the environment • Briefly discuss the steps being taken to combat acid rain

4. Drivers of acidification Pages 271-274 in Middleton • Acid rain is associated with the emission of sulphur and nitrogen during the burning of fossil fuels such as coal and oil in power stations, industrial steam boilers or generators, and motor vehicle engines. When these pollutants come into contact with water vapour, oxygen and sunlight in the atmosphere, a diluted mixture of sulphuric and nitric acid is formed. In highly industrialised regions, hydrogen chloride also forms part of this acid mixture.

5. Geography of acid deposition

6. Geography of acid deposition Pages 274-275 in Middleton • The acid rain problem is not distributed evenly across the world, mainly due to uneven distribution of industrialization • In the 1980s, the USA, Canada and Europe were the main emitters of sulphur dioxide • Shift of maximum sulphur dioxide emissions from North Atlantic to East Asia • Areas mostly affected are: • East Asia • North America • Europe • Movement of acid rain across political boundaries (transboundary air pollutants) • Examples of Sweden affected by industries in other parts of Europe and South Korea and Japan affected by industries in China

7. Effects of acid rain Pages 273 and 275-284 in Middleton • Impact of ocean acidification on marine life: • Many marine organisms have calcium carbonate (CaCO3) shells or skeletons. • As pH declines, carbonate (CO3) becomes less available, making it more difficult for organisms to form skeletal material. • Lower pH could change behaviour and reproduction of marine organisms. • Higher concentrations of dissolved CO2 could alter the ability of marine plants to conduct photosynthesis • The distribution of warm-water corals will be dramatically reduced through lower rates of calcification and more fragile skeletons

8. Effects of acid rain Acidification risk factors

9. Effects of acid rain Aquatic ecosystems • Decline and extirpation of fish populations in lakes in Canada and Norway • Increased mobilization of toxic metals into soil and waterways • Aluminium obstruct the gills of fish • Fish experience a decline in reproduction abilities • The loss of fish has knock-on effects on the food chain • Increased leaching of trace metals from acidified areas can lead to more frequent algal blooms and coastal eutrophication

10. Effects of acid rain Terrestrial ecosystems • Five ways in which vegetation can be affected by acid rain: • Increased soil acidity (Overuse of nitrogen fertilizer in China) • Change in nutrient availability (Ammonia emissions in the Netherlands) • Mobilization of toxic metals • Leaching of important soil chemicals and • Changing species composition and decomposer micro-organisms in soils • Loss of lichen and mosses in Europe • The moss-lichen layer performs many ecological functions, including the regulation of soil temperature and protection of soil from erosive processes • Reduced abundance of birds (central Pennsylvania)

11. Effects of acid rain Terrestrial ecosystems • The widespread loss of the moss-lichen layer in the Kola Peninsula, Russia, has led to extensive damage to trees and shrubs caused by frost and soil erosion • The loss of larch trees and plants in Norilsk, Russia exposed soils to severe soil erosion, which created an ‘anthropogenic desert’ • Symptoms associated with poor tree health are also linked to the effects of acid rain: • Thinning of crowns • Decreased resistance to drought, disease and frost • Damage to needles, leaves and bark

12. Effects of acid rain Examples for forest decline in Europe

13. Effects of acid rain Human health • Effects on respiratory and cardiovascular systems: • Increased mortality and impaired pulmonary (lung) function • Inhalation of aerosols and acidic vapours exacerbates the effects of asthma and the risk of bronchitis • Water contamination: • Heavy metals such as cadmium, nickel, lead, manganese and mercury may reach humans through contaminated water of fish • Heavy metals may cause brain damage and bone disorders • High levels of lead in drinking water may cause Alzheimer’s disease and senile dementia

14. Effects of acid rain Materials • Water may transport or accelerate the chemical reactions of solution and crystallization • Acid rain can accelerate the corrosion of metals and the erosion of stone • Acid rain can dissolve limestone • Limestone, marble, dolomitic and calcareous sandstone, iron and steel are corroded by SO2 • Reaction of SO2 with calcium carbonate forms gypsum, which is soluble and easily washed off the stone surface • Sulphates of chloride can crystallize and expand inside stonework, causing cracking and crumbling of the stone surface.

15. Effects of acid rain Materials • Examples: the Parthenon in Athens (picture below), the Taj Mahal in Agra, the El Tajin zone in Veracruz and marble tombstones across North America

16. Combating the effects of acid rain Pages 285-288 in Middleton • Technologies that could be used to try to limit emissions of industrial pollutants: • Fuel desulphurization, which removes sulphur from coal before burning • Fluidized bed technology, which reduces the SO2 emissions during combustion • Flue gas desulphurization, which involves removing or ‘scrubbing’ sulphur gases before they are released into the air