While that might be the poster child for such pollution, the reality is that manufacturing sources produce only about 10 percent of the nitrogren-based pollution.
The real culprit is something much more down to earth—literally.
Agriculture contributes the vast majority of this type of pollution through the use of nitrates, according to a study published in the Proceedings of the National Academy of Sciences by Professor Joshua Fu along with graduate student Jian Sun and research assistant professor Kan Huang, all of the Department of Civil and Environmental Engineering at the University of Tennessee, Knoxville.
“Air pollution is a growing concern around the world, and one that everyone is forced to pay attention to because, by nature, airborne pollutants don’t obey borders,” said Fu, who is a joint faculty member at Oak Ridge National Laboratory. “While overall nitrous oxide pollution has been reduced in the United States, nitrate pollution is really growing by leaps and bounds.
Ammonia is the troublesome compound. “It is unregulated, is widely used as a fertilizing product and has a real impact on the environment.”
Used as both a fertilizer and occurring as a result of animal byproducts, ammonia could account for more than half of the nitrogen-based pollution in some areas of the U.S., Fu and his fellow researchers have determined.
By simulating the conditions under which such nitrogen-based pollution is found, as well as its distribution once it becomes airborne, the group hopes to bring new attention to the scope of the problem.
“As the population grows, so does the demand for food,” said Fu. “As more agricultural business takes place to meet that demand, the amount of pollution from nitrogen- and nitrate-based fertilizers climbs as well.
“We have to be able to better understand the effects of this type of pollution and to come up with alternative methods that help control it without hurting food production.”
In addition to ammonia, Fu and his fellow researchers think that organic nitrates and other oxidized nitrogen compounds should be counted as contributing to nitrogen-based pollution.
To curb pollution without impacting food supplies, Fu and his colleagues are using the powerful Titan computer at ORNL to help model more accurate outcomes.
Fu’s team looked at both “dry deposits” and “wet deposits” of nitrates. While wet deposits tend to be more localized, dry deposits have a much easier time disseminating through the air, spreading their impact far beyond what was previously known.
Working together with the National Atmospheric Deposition Program, the team will now use the data to better understand these issues and come up with solutions.