Although the mass production and use of chemicals have brought prosperity, they have also caused environmental problems. We will learn about major environmental problems and their chemical mechanisms.
Basic Knowledge
Major environmental problems and causative substances:
① Global warming: A problem in which the average temperature of Earth rises as greenhouse gases such as carbon dioxide (CO2), methane (CH4), and chlorofluorocarbons increase in the atmosphere.
② Acid rain: A problem in which sulfur dioxide (SO2) and nitrogen oxides (NOx) produced by burning fossil fuels react with water in the atmosphere to form sulfuric and nitric acids, causing rain with a pH of 5.6 or lower. It causes forest death and acidification of lakes.
③ Ozone-layer depletion: A problem in which chlorofluorocarbons (CFCs) reach the stratosphere and decompose ozone (O3), increasing ultraviolet radiation.
④ Eutrophication: A problem in which nitrogen and phosphorus compounds flow into lakes and seas, causing abnormal growth of plankton and deterioration of water quality.
Greenhouse gases (CO2, CH4, chlorofluorocarbons, and others. Absorb infrared radiation and warm the atmosphere)
Acid rain (caused by SO2 and NOx. Rain with a pH of 5.6 or lower)
Ozone layer (a layer of O3 in the stratosphere. Absorbs harmful ultraviolet radiation)
Chlorofluorocarbons (CFCs) (once used as refrigerants and propellants, but destroy the ozone layer)
Microplastics (tiny pieces of plastic 5 mm or smaller. A major cause of marine pollution)
Carbon neutrality (the goal of making net CO2 emissions zero by balancing emissions and absorption)
Further Study
To prevent global warming, the Paris Agreement (2015) set the goal of limiting the rise in temperature to 1.5℃ compared with the preindustrial level. Japan has declared that it will achieve carbon neutrality by 2050.
Serious damage from acid rain has been observed in Europe, including Scandinavia and Germany, and in China, leading to the destruction of lake ecosystems and corrosion of buildings. Regulation of CFCs began with the Montreal Protocol, which entered into force in 1989. Although the transition to alternative refrigerants (HFCs) progressed, HFCs themselves were found to be powerful greenhouse gases, so further regulations, including the Kigali Amendment, were introduced.
- Main cause of global warming = increase in greenhouse gases such as CO2 and CH4
- Causes of acid rain = SO2 and NOx (from burning fossil fuels)
- Cause of ozone-layer depletion = chlorofluorocarbons (CFCs)
- CFCs are regulated by the Montreal Protocol
- The Paris Agreement (2015) set the 1.5℃ goal
- Eutrophication = inflow of N and P compounds → red tides and algal blooms
- Microplastics = 5 mm or smaller and a marine pollution problem
Points to Note
① Global warming (increase in CO2) and ozone-layer depletion (CFCs) are separate problems. CFCs also have a greenhouse effect, but the main problems are distinct. ② Acid rain has a pH of 5.6 or lower (ordinary rain has a pH of about 5.6 because CO2 dissolves in it). ③ Eutrophication is caused by N (nitrogen) and P (phosphorus), not carbon.
Practice
- Answer two gases that cause acid rain using their chemical formulas.
- What is the main substance that destroys the ozone layer?
- Name one international agreement intended to prevent global warming.