Chemistry of the Environment - Air quality and climate

The atmosphere is a mixture of gases: approximately $78\%$ Nitrogen ($N_2$), $21\%$ Oxygen ($O_2$), $0.9\%$ Argon ($Ar$), and $0.04\%$ Carbon dioxide ($CO_2$).

Pollutants such as Carbon monoxide ($CO$) are produced by the incomplete combustion of carbon-containing fuels, while Sulfur dioxide ($SO_2$) is produced from the combustion of fossil fuels containing sulfur compounds.

Oxides of nitrogen ($NO_x$) are formed in car engines where high temperatures and pressures cause the $N_2$ and $O_2$ from the air to react.

Particulates, such as unburnt carbon (soot), are produced by incomplete combustion and can cause respiratory problems and global dimming.

The greenhouse effect is caused by gases like Carbon dioxide ($CO_2$) and Methane ($CH_4$) absorbing thermal energy (infrared radiation) and re-emitting it back towards Earth, leading to global warming.

Ocean acidification occurs when increased levels of $CO_2$ dissolve in seawater to form carbonic acid ($H_2CO_3$), which lowers the $pH$ and affects marine life like coral reefs.

Catalytic converters in vehicles reduce the emission of toxic gases by providing a surface for reactions that convert $NO_x$ and $CO$ into $N_2$ and $CO_2$.