Pollution acid (or acid rain) is related to acidic pollutants (SO2, NOx, NH3, HCl, HF) emitted by human activities that fall in part to proximity to sources, but also to hundreds or thousands of kilometers of their emitting sources. These pollutants fall as wet or dry deposition. During transport, these pollutants are changing. SO2 and NOx are converted into sulphates (SO 4 2 -) and nitrate (NO 3 2 -) where the atmosphere is dry, as well as sulfuric acid (H 2 SO 4) and nitric acid ( HNO 3) where the atmosphere is humid.
The phenomena of acid pollution on a large scale have been highlighted by the acidification of lake waters Scandinavians and Canadians. The pH of water became acid causing significant changes in the fish fauna. Some rain has a pH between 3 and 4, while pure water has a pH of 5.6. Acid deposition have effects on materials, forest ecosystems and freshwater ecosystems.
Eutrophication:-
Eutrophication is a disturbance of the biological equilibrium of soil and water due to excess nitrogen including atmospheric (NOx and NH3) over the absorption capacity of ecosystems.
Photochemical pollution
Photochemical pollution (pollution or photochemical) is a complex set of phenomena that lead to the formation of ozone and other oxidizing compounds (hydrogen peroxide, aldehydes, peroxy acetyl nitrate or PAN) from primary pollutants ( called precursors) of nitrogen oxides and volatile organic compounds (VOCs) and energy provided by the Ultra Violet radiation (UV) solar. These phenomena occur in the layers of air near the ground and in the free troposphere. Ozone in the stratosphere (19-30 km altitude), the opposite is called “good ozone” because it protects us from solar UV radiation.
Surprisingly, concentrations of ozone measured away from sources of precursors (eg agglomeration) are higher than those measured near the sources. Indeed, on a city for example, emissions of NO (relating to trafficking in particular) are high. Ozone is destroyed by NO. If the cloud of pollutants formed in the city moves to the countryside, or NOx emissions are reduced, ozone concentrations increase because more ozone is consumed. Photochemical pollution is a phenomenon characteristic of the summer anticyclonic situations.
Ozone’s effects on human health, ecosystems, forestry and agriculture, over this phenomenon of photochemical air pollution is closely linked to acid rain.