Flemish Environment Agency (VMM)
Potentially acidifying emissions: sum of the emissions of sulphur dioxide (SO2), nitrogen oxides (NOx (NO2)) and ammonia (NH3). This sum is expressed in acid equivalents (Aeq), taking into account the acid-forming capacity of each substance. The term ‘potentially’ acidifying emissions is used because the actual acidification also depends to a large extent on the processes involved between emission and deposition and on the various processes in the soil and (surface) water.
In addition to their role as potentially acidifying substances, NH3, NOx and SO2 also play a role in the formation of secondary particulate matter via aerosol formation. NOx is an ozone precursor and NH3 and NOx have a eutrophying effect.
Remarks on quality
The data inventory is based on mandatory information collection such as annual environmental reports, collective emissions registration, scientific studies, statistical information (e.g. traffic and agricultural declarations), internationally accepted or regional emission factors, etc. An inventory is always the most complete and correct estimate of the data at a particular moment. This does not mean, however, that there are no uncertainties in the figures. It is currently not possible to allocate a specific margin of uncertainty to the various datasets.
Data managers rely on the latest scientific findings and on international agreements concerning methods to compile complete, consistent and validated time series. Consequently, the most recent datasets can differ from those in previous reports. A recalculation is always done for all historical years, so that a consistent time series is maintained.
Flanders Environment Agency (VMM): Acidifying emissions