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A lake in northern Florida with degraded water quality and ecosystem damage due to elevated reactive nitrogen concentrations. Brian G. Katz / Eos

World - Exploring the Widespread Impacts of Ongoing Nitrogen Pollution

The release of reactive nitrogen into the environment is having severe and ongoing ecosystem, economic, and human health impacts. How can we reduce our nitrogen footprint?

Nitrogen is one of the most important nutrients in the environment, but its natural cycling has been significantly altered by human activities; specifically the release of excessive and harmful amounts of nitrogen from various sources including fertilizers, animal and human wastes, fossil fuel combustion, and mining. Nitrogen Overload: Environmental Degradation, Ramifications, and Economic Costs, a new book recently published by AGU, seeks to improve our understanding of the negative impacts of so much excess reactive nitrogen in the environment. Here the author, Brian G. Katz, a scientist who has spent the past four decades investigating the transport and fate of nitrogen in groundwater, springs, surface waters, and the atmosphere, gives an overview of the main issues.

Why is nitrogen an interesting element to study in the environment?

Nitrogen is an essential component of the building blocks of life (DNA, RNA, and proteins) and exists in many different forms in the environment. It transforms and moves between the atmosphere, biosphere, and hydrosphere.

As dinitrogen gas (N2) it is the most abundant element in Earth’s atmosphere (and the air that we breathe) making up 78% of all gases by volume. However, rather ironically, this bountiful form of nitrogen (N2 gas) is unusable by most organisms.

N2 gas is essentially unreactive due to the strong triple bond between the nitrogen atoms in the nitrogen gas molecule. Fortunately, certain specialized nitrogen-fixing microorganisms in soils can transform or convert nitrogen gas to forms that are reactive and available to plants (e.g. ammonium, nitrate), thereby providing sustenance to all animal life on this planet. These transformation processes by microorganisms are referred to as biological nitrogen fixation.

When was artificial nitrogen first created, how has it been used, and what impact has it had?  

Prior to the 19th century, the reactive nitrogen produced naturally by biological nitrogen fixation and abiotic processes (e.g. lightning) was balanced by plant uptake and nitrogen removal (denitrification) processes, and therefore did not accumulate in the environment.

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