Satellite study finds ammonia hotspots over agricultural areas

A satellite study of airborne ammonia gas has revealed four major hotspots over productive agricultural regions across the world. Increased atmospheric ammonia is linked to poor air and water quality.

Using data from NASA’s Atmospheric Infrared Sounder satellite instrument, researchers led by the University of Maryland (UMD), discovered increased ammonia concentrations from 2002 to 2016 over agricultural centres in the US, Europe, China and India. The study was published last month in the journal, Geophysical Research Letters.

Harmful effects

Increased ammonia is linked to fertilizers, livestock animal wastes, changes in atmospheric chemistry and warming soils that retain less ammonia.

Gaseous ammonia is a natural part of the Earth’s nitrogen cycle, but excessive ammonia is harmful to plants, the study adds. Ammonia gas can also fall back to Earth and waterbodies, where it contributes to harmful algal blooms and “dead zones” with dangerously low oxygen levels.

“To control ammonia-related pollution, it is necessary to regulate fertilizer waste and agricultural residue burning. Increase in fertilizer use is the leading cause behind the increase of gaseous ammonia in the atmosphere. Except for a few countries in Europe, ammonia emission is not regulated. There is a growing awareness on how ammonia in the atmosphere affects the ecosystem and air and water quality, Juying Warner, associate research scientist in atmospheric and oceanic science at UMD, told Down To Earth.

According to researchers, the study results could help formulate strategies to control ammonia pollution near major agricultural areas.

Bad news for India

According to Warner, the ammonia concentration in the atmosphere over India is the highest in the world due to cattle population and excessive fertilizer use. “This will contribute to increased air quality problems,” she warned.

The use of nitrogen fertilizers has grown worldwide, contributing to the growing demand for food. Where fertilizers are subsided, the regulation of the fertilizer use is the biggest challenge.

“Subsidies lead to low price of fertilizers, farmers also tend to over-apply because they don’t want to take the risk of low yields,” Aimable Uwizeye, Food and Agriculture Organization expert, says.

According to Uwizeye, the best ways to reduce ammonia emissions are improvement in manure management system, reduction of excessive nitrogen in animal diets and recycling of manure in crop systems. Storage of manure with minimum risk of run-off and seepage as well as prevention of leaching to water bodies and riparian buffer zones is necessary to reduce ammonia emissions.

In India, we can try to improve the digestibility of protein compound in animal feed to reduce ammonia emissions. Uwizeye adds one should prioritise nitrogen use efficiency in livestock systems, identify hotspots and explore country-specific approaches to reduce ammonia pollution.

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India Environment Portal Resources :

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• Reduction of national emissions of atmospheric pollutants
• Ammonia oxidizing bacteria community dynamics in a pilot-scale wastewater treatment plant
• Reducing uncertainty in nitrogen budgets for African livestock systems