A new paper published on 5 December in Nature presents the first global map of the distribution of atmospheric ammonia (NH3) based on satellite data (1). The new data has now allowed scientists to identify more than 200 ammonia hotspots associated with livestock production and industrial activities.
Ammonia is one of the major components of smog and when released into the atmosphere, ammonia has an unpleasant smell, even at low concentrations. At high concentrations, ammonia can significantly degrade air quality ― with important implications for human health ― and harm vegetation. In bodies of water, ammonia pollution is even more serious since ammonia is highly toxic to aquatic organisms. Despite the detrimental impact of industrial and agricultural ammonia pollution, the total ammonia budget remains uncertain and emissions have not previously been attributed to specific sources, especially on a local scale.
Typically, ammonia only stays in the atmosphere for less than a day before reacting with other molecules to become particulate matter. Amonnia is responsible for about 60% of particulate air pollution in the European Union. As such, targets have been set to reduce ammonia emissions by 6% by 2020, relative to 2005 levels.
To map the global distribution of atmospheric ammonia (NH3), scientists from the Centre National de la Recherche Scientifique (CNRS) in Paris and the Universite Libre de Bruxelles (ULB) in Brussels analysed interferometer measurements taken by satellites between 2008 and 2016. The Infrared Atmospheric Sounding Interferometer (IASI) interferometer was developed by the French space agency (CNES). The authors reported 248 hotspots to within a one square kilometre resolution. Then, by combining information from visible imagery, publicly available, inventories, and online sources, the hotspots were classified as either agricultural, industrial, or natural.
All of the identified hotspots could be associated with a single point source or a cluster of agricultural and industrial point sources―except one hotspot traced back to a natural source. According to the authors, the findings suggest emission inventories of anthropogenic ammonia sources should be reassessed to account for the rapid evolution of these sources over time.
The 83 agricultural hotspots were consistently shown to be associated with intensive animal farming, including open feedlots or enclosed housings with mostly large concentrations of cows, pigs, or chickens. The 158 hotspots in the industrial emitters class were mostly traced back to plants producing ammonia-based fertilizer ― over 130 sites. The third class, natural emissions, come from oceans, non-agricultural soils, and plants.
The most interesting part of the study was that out of more than 200 sources of ammonia the researchers were able to catalogue, two-thirds of these had not been identified previously. The newly identified sources were mainly attributed to intensive livestock production and industrial activity ― the increasing use of fertilizer and meat production is increasing ammonia levels. Furthermore, the report showed that levels of emissions from previously identified sources are greatly underestimated.
This latest study has highlighted that industrial and agricultural ammonia pollution can be significant and are often an overlooked source of emissions. It is hoped that the new data will lead to improved health and environmental impact assessments of atmospheric ammonia and will enable policymakers to implement suitable nitrogen management strategies.
(1) Van Damme, M. et al. Industrial and agricultural ammonia point sources exposed. Neture (2018). DOI: 10.1038/s41586-018-0747-1