Restricting Ammonia Emissions Not Enough to Control Nitrogen Deposition

While nitrogen is an essential element in nature, excessive amounts of nitrogen, mostly coming from human activities like combustion and use of fertilizer, has shown negative impacts on the ecosystems and human health.

Due to the decline in nitrogenous air pollution by the successful implementation of the Clean Air Act, emission abatement has been recognized as an efficient means to bring down the acid deposition level on the earth’s surface, especially with nitrogen oxide and ammonia.

However, new research led by John D. Tickle Professor Joshua Fu published in Proceedings of the National Academy of Sciences of the United States of America (PNAS) shows that the deposition rate of ammonium nitrogen (ammonia gas and ammonium particles) is unlikely to drop at the early stages of implementing abatement of ammonia emission. Analysis based on both monitoring and modeling illustrates that reduction of ammonia emission, along with the current emission control policies on sulfur dioxide and nitrogen oxide emissions, may not lead to full improvement in ammonium nitrogen deposition over continental regions of the US.

The study offers important information to the community and policymakers concerning nitrogen deposition, given the urgent needs for developing control strategies on ammonia emissions.

For the past few years, Fu’s group has published a series of studies to raise public awareness on the rapid increases of ammonium nitrogen deposition. The results of the present study for the US are likely applicable to regions with intensive ammonia gas deposition rates over the world.