A Detailed Look at Reactive Nitrogen

Archive—In case you missed's a look back at the September 2015 issue of EM, which examined various aspects of reactive nitrogen and potential management approaches, both from a North American and European perspective.
by Christian Hogrefe

Nitrogen is one of the building blocks of life, yet excessive amounts in the environment can cause problems in various ecosystems. Abundant in the atmosphere as dinitrogen (N2), nitrogen needs to be combined with other elements such as hydrogen or oxygen to form compounds collectively known as reactive nitrogen before it can be used by most living organisms. This process is referred to as fixation. Natural pathways for creating reactive nitrogen are biological fi xation by algae and bacteria hosted by leguminous crops such as soybeans and alfalfa, as well as the production of nitrogen oxides from lightning. Man-made pathways include the production of synthetic fertilizer through the Haber-Bosch process and the combustion of fossil fuels.

The advent of synthetic fertilizer production in the early 20th century has increased food security around the globe and has helped support a growing global population. However, increasing use of synthetic fertilizer, as well an increase in livestock, have also had adverse effects on aquatic ecosystems through run-off and leaching that can lead to eutrophication of waterbodies. The burning of fossil fuels has led to changes in atmospheric
chemistry and composition which, in turn, can affect concentrations of harmful pollutants such as ozone, alter the radiative balance of the atmosphere, contribute to changes in stratospheric ozone levels, and lead to acidifi cation of terrestrial and aquatic ecosystems through deposition.

A single molecule of reactive nitrogen, created through natural or man-made processes, can cycle through various environmental systems—the atmosphere, terrestrial ecosystem, and aquatic ecosystems—where it can be transformed or temporarily stored. As it moves through these systems, it can change the behavior of these systems and, thereby, also affect human health and well-being. This movement through the different environmental systems following the initial creation of reactive nitrogen is often referred to as nitrogen cascade. Since the starting point of this cascade often is related to human activity, a part of the solution to address imbalances in the reactive nitrogen cycle may include choices about our lifestyle, most notably by reconsidering the dietary choices we make and the amount of energy we use in our daily lives.

The six articles in this issue examine various aspects of reactive nitrogen and potential management approaches, both from a North American and European perspective.
Members can read the full September 2015 issue of EM.