6.3c Air Pollution and Acid Precipitation

What is acid rain?

Acid Precipitation §  has a pH of less than that of natural rainwater

(pH 5.6)

§  a decrease of 1.0 on the pH scale means a 10-fold increase in the amount of acid present

Acid Rain

Causes of Acid Rain §  Natural Sources

§ effects of acidic deposits have been found in

glacial ice in remote parts of the globe

§ emissions from volcanoes and other biological processes contribute acid-producing gases

Acid Rain §  principal cause of acid rain is from human sources

§ burning fossil fuels (e.g. coal) § driving cars § producing materials in factories

The Problem with Combustion §  burning fossil fuels produces sulfur dioxide (SO2) (very

poisonous gas)

§  cars and power plants produce nitrogen oxides (NOx)

§  when SO2 and NOx are released into the atmosphere, they combine with H2O to form acids

§  SO2 and NOx may also be carried long distance by wind

§  these acids then enter the water cycle and fall to the Earth in the form of rain or snow (acid precipitation)

Formation of Acid Rain

The Effects of Acid Precipitation

§  Acid precipitation eats away at marble, metal, plastics, and rubber §  Parthenon in Athens, Greece §  Taj Mahal in Agra, India

Effects of Acid Precipitation on Aquatic Life

§ Increased acidity in water § Stops eggs from hatching (e.g. fish) § Changes population ratios § Affects ecosystems

Example: Lake Trout

Overall, the number of species in the lake at pH 5.1 was 30% lower than normal

1979 – pH 5.6 1982 – pH 5.1

Effects of Acid Precipitation on Vegetation

§ Increased acidity in soil § Slows plant growth § Poisons plants § Creates brown spots in leaves of trees,

(interferes with photosynthesis) § Increases probability of infection through

broken leaves

Effects of Acid Precipitation on Vegetation

The Effects of Acid Precipitation on Humans

§ Respiratory problems § Asthma § Dry coughs § Headaches § Throat irritations

Preventive Measures §  Reduce SO2 and NOx released into the atmosphere

§  Use less energy (hence less fuel burnt)

§  Use cleaner fuels

§  Use other sources of electricity (i.e. nuclear power, hydro-electricity, wind energy, geothermal energy, and solar energy)

§  Reduce reliance on cars (car-pooling, public transport, bicycle)

Homework §  Read 6.3 (236-246)

§ Q 2-5, 7 (p.246)