In its inert form, nitrogen is harmless and abundant, making up 78 percent of the Earth's atmosphere. But in the past century, with the mass production of nitrogen-based fertilizers and the large-scale burning of fossil fuels, massive amounts of reactive nitrogen compounds, such as ammonia, have entered the environment.
"A unique and troublesome aspect of nitrogen is that a single atom released to the environment can cause a cascading sequence of events, resulting ultimately in harm to the natural balance of our ecosystems and to our very health," Galloway said.
A nitrogen atom that starts out as part of a smog-forming compound may be deposited in lakes and forests as nitric acid, which can kill fish and insects. Carried out to the coast, the same nitrogen atom may contribute to red tides and dead zones. Finally, the nitrogen will be put back into the atmosphere as part of the greenhouse gas nitrous oxide, which destroys atmospheric ozone.
Galloway and his colleagues suggest possible approaches to minimizing nitrogen use, such as optimizing its uptake by plants and animals, recovering and reusing nitrogen from manure and sewage, and decreasing nitrogen emissions from fossil fuel combustion.
"Nitrogen is needed to grow food," Galloway says, "but because of the inefficiencies of nitrogen uptake by plants and animals, only about 10 to 15 percent of reactive nitrogen ever enters a human mouth as food. The rest is lost to the environment and injected into the atmosphere by combustion.
"We must soon begin to manage nitrogen use in an integrated manner by decreasing our rate of creation of reactive nitrogen while continuing to produce enough food and energy to sustain a growing world population.
Galloway's next effort is to create a "nitrogen footprint" calculator that people can access on the Internet, very similar to current "carbon footprint" calculators.
He says people can reduce their nitrogen footpri
|Contact: James Galloway|
University of Virginia