Air pollutants

What is the composition of clean air?

78% = N2

21% = O2

1% = Rare gases, mainly Ar

0.03% = CO2

What observations can be made from SO2?

Pungent, colourless gas

What are the sources of SO2?

• Combustion off fossil fuels

• Volcanic eruptions

What are the harmful effects of SO2

• Causes breathing difficulties in humans and animals

• Reacts with NO/NO2 to form acidic compounds that dissolve in rainwater, forming acid rain i.e. solutions of strong acids

What are the harmful effects of acid rain?

• Kills plant and aquatic life

• Corrodes building and structures made from limestone, marble and metals

What observations can be made from NO?

Colourless, odourless gas

What observations can be made from NO2?

Pungent, red-brown gas

What are the sources of NO/NO2

• Vehicle combustion engines

• Lightning

What are the harmful effects of NO/NO2?

• Reacts with SO2 to form acidic compounds which dissolve in rainwater, forming acid rain i.e. solutions of strong acids

What observations can be made from CO?

Colourless, odorless toxic gas

What are the sources of CO?

Incomplete combustion of carbon-based fuels

What are the harmful effects of CO?

Binds irreversibly with haemoglobin in RBCs, lowering their ability to transport oxygen to the rest of the body, resulting in loss of consciousness or even death

What observations can be made from CH4?

Colourless, odourless and highly flammable gas

What are the sources of CH4?

• Anaerobic bacterial decay of organic substances

• Waste gases from cattle

What are the harmful effects of CH4?

Leads to global warming as a major greenhouse gas

What observations can be made from unburnt hydrocarbons (CxHy)?

Colourless, naturally odorless gases that may be pungent due to fuel additives

What are the sources of unburnt hydrocarbons (CxHy)?

Vehicle combustion engines

What are the harmful effects of unburnt hydrocarbons (CxHy)

• Can cause eye and respiratory tract irritation

• Reacts with NO/NO2 in the presence of sunlight to form photochemical smog which appears as brown haze. Smog produces SO2 and NO2

What observations can be made from O3?

Pungent, pale blue gas

What are the sources of O3?

• Lightning

• Reactions between O2 molecules and sunlight in the upper atmosphere

• Reactions between CxHy and NO/NO2 in the presence of sunlight in the lower atmosphere

What are the harmful effects of O3?

• Can cause eye and respiratory tract irritation, leading to breathing difficulties

• When inhaled, can cause chest pain and headaches

• Slows down photosynthesis in plants, damaging crops

How does acid rain kill plants?

• Leaches essential nutrients like magnesium and calcium from the soil, which hampers the health and growth of trees

• Lowers the pH of soil below what plant species can tolerate

How does acid rain kill aquatic organisms

Addition of acid rainwater to a water body can cause pH to drop out of a survivable range. Water bodies become less biodiverse