Ammonia
Air quality NH₃ ammonia gas
Ammonia, NH₃, is a nitrogen-containing gas. Agriculture is its main outdoor source, and it contributes to the formation of particulate matter.
How ammonia reaches the air
Livestock, manure and nitrogen fertilisers can release ammonia. Other biological and industrial processes emit it too. Emissions depend partly on the material, application method, temperature and weather.
A gas can become particles
Ammonia reacts with acidic substances in the air to form ammonium salts. These can contribute to PM2.5. Agricultural emissions therefore affect air quality beyond the immediate field or farm.
Why nitrogen is not welcome everywhere
When ammonia and its products enter soils or water, they add nitrogen. A nutrient useful to a crop can alter ecosystems adapted to low nutrient levels. Subsequent processes can also contribute to soil acidification.
What the model value means
Concentrations usually use µg/m³. Wind transports and disperses the gas, while uptake by surfaces and precipitation can remove it. A regional forecast cannot tell you whether a particular street currently smells of manure. Conversely, an odour is not a precise concentration measurement.