Page last updated : 30/06/2010

Acid equivalent - Aeq

This index aims to assess the overall amount of acidifying substances emitted into the atmosphere. At different spatial and temporal scales, these substances contribute to the acidification of soil, air and the aquatic environment. It is based on the potential fixation of H+ ion. The calculation only takes into account SO₂, NOx and NH₃, because it is quite obvious that other acidifying substances such as HCl, only have a marginal effect, given their low emissions level compared to the other three substances. The index is calculated by using weighted coefficients : 0,0313 for SO₂, 0,0217 for NOx and 0,0588 for NH₃.

Source : CITEPA / SECTEN format - April 2010

Survey period : since 1980

Comments

The following figures show the distribution between the pollutants for the Acid equivalent has changed during the years. In 1980, Aeq emissions were mainly due to SO₂ (52%), whereas in 2008, SO₂ emissions represent only 14% of total Aeq emissions. On the contrary, ammonia weighted 25% in 1980 versus 53% in 2008 of these emissions.