Maintaining Air Quality — Study Materials Flashcards

Front

Dry air composition

Back

Dry air is approximately 78% nitrogen, 21% oxygen, with the remainder composed of noble gases (mainly argon) and small amounts of carbon dioxide. These percentages refer to volume composition under standard atmospheric conditions.

Front

Fractional distillation

Back

Fractional distillation separates gases by their different boiling points after air is liquified at very low temperatures. As the mixture warms, components boil off in sequence (e.g., nitrogen first, then argon, then oxygen) and are collected.

Front

Carbon monoxide (CO)

Back

Carbon monoxide is a toxic, colorless, odorless gas formed by incomplete combustion of carbon-containing fuels. It binds irreversibly to haemoglobin, reducing oxygen transport and causing headaches, fatigue, and potentially death.

Front

Nitrogen oxides (NOx)

Back

Nitrogen oxides (NO and NO2) form at high temperatures in engines and during lightning strikes when N2 and O2 react. They irritate the respiratory system and contribute to acid rain and photochemical smog.

Front

Sulfur dioxide (SO2)

Back

Sulfur dioxide is produced from volcanic eruptions and combustion of sulfur-containing fossil fuels such as coal and crude oil. It can form acid rain and cause respiratory irritation.

Front

Photochemical smog

Back

Photochemical smog forms when nitrogen dioxide and unburnt hydrocarbons react in sunlight to produce ozone and other oxidants. It causes brown haze and respiratory irritation, and is common in sunny urban areas with vehicle emissions.

Front

Incomplete combustion

Back

Incomplete combustion occurs when fuels burn with limited oxygen, producing CO and unburnt hydrocarbons. Ensuring sufficient oxygen and using catalytic converters reduces these pollutants.

Front

Methane (CH4)

Back

Methane is a potent greenhouse gas produced by the decay of organic matter, landfill emissions, and enteric fermentation in cattle. It traps heat in the atmosphere much more effectively per molecule than CO2.

Front

Acid rain

Back

Acid rain forms when SO2 and NO2 oxidise and dissolve in rainwater to form sulfuric and nitric acids, lowering rain pH and damaging ecosystems and buildings. It reacts with metal and carbonate materials, and can kill aquatic life if pH falls sufficiently.

Front

Liming

Back

Liming involves adding calcium carbonate (CaCO3) to soils or water bodies to neutralise acidity from acid rain. It temporarily raises pH and mitigates damage but is costly and not a permanent solution for large areas.

Front

Catalytic converter

Back

A catalytic converter contains platinum, palladium and rhodium catalysts in a honeycomb structure to increase surface area and speed up redox reactions. It converts CO, NOx and hydrocarbons into less harmful gases such as CO2, N2 and H2O.

Front

Flue gas desulfurisation

Back

Flue gas desulfurisation removes SO2 from power plant exhaust using wet scrubbing with a CaCO3 slurry. SO2 reacts to form CaSO3 and then CaSO4 (gypsum), which can be used in building materials.

Front

Low-sulfur fuels

Back

Low-sulfur fuels reduce SO2 emissions without large flue gas treatment systems, making them practical for vehicles. Sulfur can be chemically removed (e.g., hydrogen treatment) but this produces hydrogen sulfide as a byproduct and can be costly.

Front

Ozone layer

Back

The stratospheric ozone layer (about 15–30 km above Earth) absorbs harmful UV radiation, protecting life. O3 in the stratosphere is formed and destroyed naturally in a cycle that filters UV light.

Front

Chlorofluorocarbons (CFCs)

Back

CFCs are stable, light compounds once used in aerosols and refrigerants that can reach the stratosphere and release Cl atoms under UV irradiation. These Cl atoms catalyse ozone destruction, causing ozone layer depletion and increased surface UV.

Front

Carbon cycle

Back

The carbon cycle balances CO2 via processes like photosynthesis, respiration, combustion and ocean uptake. Photosynthesis removes CO2 to form glucose, respiration and combustion return CO2 to the atmosphere, and oceans and sediments store carbon.

Front

Greenhouse effect

Back

The greenhouse effect is the trapping of heat by gases (mainly CO2 and CH4) in the atmosphere, keeping Earth warm enough for life. Excess greenhouse gases from human activity enhance this effect, causing global warming.

Front

Global warming

Back

Global warming is the sustained rise in Earth’s average surface temperature due to increased greenhouse gas concentrations. Consequences include changing rainfall patterns, more extreme weather, melting ice caps and sea-level rise.

Front

Ocean acidification

Back

Ocean acidification occurs when oceans absorb more CO2, forming carbonic acid that lowers pH and reduces carbonate ions. This harms organisms that build shells from carbonates, such as corals and molluscs.

Front

Glacial retreat

Back

Glacial retreat is the shrinking of glaciers and polar ice due to rising temperatures, reducing freshwater storage and contributing to sea-level rise. It can disrupt freshwater supplies, ocean currents, and coastal communities.