Public Release: 16-Mar-2017
Multi-year study finds 'hotspots' of ammonia over world's major agricultural areas
Fertilizers, animal waste, changes to atmospheric chemistry and warming soils all tied to increased ammonia over US, Europe, China and India
University of Maryland
The first global, long-term satellite study of airborne ammonia gas has revealed "hotspots" of the pollutant over four of the world's most productive agricultural regions. Using data from NASA's Atmospheric Infrared Sounder (AIRS) satellite instrument, the University of Maryland-led research team discovered steadily increasing ammonia concentrations from 2002 to 2016 over agricultural centers in the United States, Europe, China and India. Increased atmospheric ammonia is linked to poor air and water quality.
The study, published March 16, 2017 in the journal Geophysical Research Letters, also describes the probable causes for increased airborne ammonia in each region. Although the specifics vary between areas, the increases in ammonia are broadly tied to crop fertilizers, livestock animal wastes, changes to atmospheric chemistry and warming soils that retain less ammonia. The results could help illuminate strategies to control pollution from ammonia and ammonia byproducts near agricultural areas.
Gaseous ammonia is a natural part of Earth's nitrogen cycle, but excess ammonia is harmful to plants and reduces air and water quality. In the troposphere--the lowest, densest part of the atmosphere where all weather takes place and where people live -- ammonia gas reacts with nitric and sulfuric acids to form nitrate-containing particles that contribute to aerosol pollution that is damaging to human health. Ammonia gas can also fall back to Earth and enter lakes, streams and oceans, where it contributes to harmful algal blooms and "dead zones" with dangerously low oxygen levels.
"Little ammonia comes from tailpipes or smokestacks. It's mainly agricultural, from fertilizer and animal husbandry," said Russell Dickerson, a professor of atmospheric and oceanic science at UMD. "It has a profound effect on air and water quality -- and ecosystems. Here in Maryland, ammonia from the atmosphere contributes as much as a quarter of the nitrogen pollution in the Chesapeake Bay, causing eutrophication and leading to dead zones that make life very difficult for oysters, blue crabs and other wildlife."