The extent of the emission depends on the production of these acids, hence the time series will reflect production levels.
Emissions arise from agricultural soils and manure management.
The former is based on fertilizer use and the cultivated areas of certain crops. The latter reflects the general variation in livestock numbers. The contribution from public power derives mainly from coal combustion and has declined with the gradual change from coal fired generation to gas fired stations. Emissions from road transport are increasing as a result of the increasing numbers of petrol driven cars fitted with three way catalytic converters. The contribution from petrol vehicles has risen by a factor of 3 since 1990.