Many pollutants reach us by way of the atmosphere, and they end up affecting us and the environment in many different ways. We release a number of toxic compounds into the atmosphere, such as PAHs, CFCs, particulate matter and tropospheric ozone (sometimes called ground-level ozone).
- Sulphur dioxide (SO2) is formed when oil and coal with a high level of sulphur is burned. SO2 reacts with oxygen and water to form sulphuric acid (H2SO4), and can also for sulphate ions (SO42-) in the atmosphere.
Nitrogen oxides (one often refers to these as NOx since a mixture of NO and NO2 is formed). Chemically it can be summarised as NO + O3 → NO2 + O2
4NO2 + 2H2O + O2 → 4HNO<sub3</sub>
Also the base ammonia can act as an acid, when it is oxidised by bacteria. </ul> In all water we have some carbon dioxide, which forms carbonic acid (H2CO3) in water. The carbonic acid then takes part in a buffer system with HCO3–. When excess acid is added to the lake the HCO3– ions are not replaced quickly enough and the pH plunges. The low pH in turn is detrimental in many ways, e.g Al3+ is released from minerals in the soil, but may also increase the release of heavy metals.
Eutrophication is the process when added nutrients (nitrogen and phosphorous) to a lake or river causes a bloom of algae (phytoplankton). It is common on lakes and coastal waters. This affects the marine and fresh water ecosystems adversely.
Sources for nitrogen and phosphorous is mostly agriculture (i.e. fertiliser that is transported with water runoff). There are no easy solutions to this, but better techniques in farming can drastically improve the losses to runoff: this benefits both the farmer (less fertiliser needs to be purchased) and the environment.
Different gases have different Global warming potential, with takes both longevity i the atmosphere and ability to trap heat into account. A table with some common gases and their GWP can be found here.