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Last changed: 18/02/11
Reactive nitrogen, unlike nonreactive molecular nitrogen (N2), is in a great many organic and inorganic substance compounds and of vital importance to all life processes. The availability of reactive nitrogen often limits plant growth, which is why sufficient supply of reactive nitrogen is so important in food production. If excessive amounts of reactive nitrogen are deposited to the environment, however, it poses a danger to human health and the viability of ecosystems.
Forms of reactive nitrogen which are especially relevant to the environment are
The different forms of reactive nitrogen are very mobile and can convert into one another. They circulate in a biogeochemical cycle between air, soil, water and organisms.
Some 50% of the planet’s nitrogen supply is in gaseous atmospheric nitrogen compounds. The majority of it (more than 99%) is the inert molecular nitrogen, a chemical form that is not usable by most organisms including plants. In the prehuman world molecular nitrogen was converted to reactive nitrogen primarily by a very few bacterial strains. Since the age of the Industrial Revolution, however, human activities have caused far more elemental nitrogen to change into reactive forms, probably at a rate ten times higher than in the pre-industrial era. The major conversion processes are
The excessive release of reactive nitrogen compounds disrupts natural biogeochemical cycles and the delicate balance in ecosystems, which results in considerable negative consequences for man and the environment.
Because of the mutability of nitrogen, reduction measures in one environmental medium might shift an existing problem to another area to become more acute there. Effective reduction of reactive nitrogen compound emissions and corresponding adverse environmental impact requires adoption of integrated concepts. Against this background the German Federal Environment Agency (Umweltbundesamt) developed an Integrated Strategy for the Reduction of Nitrogen Emissions for Germany in 2009. Recently, there has been heightened development of supraregional and cross-cutting approaches to solving the problem at both European and international level.
Agriculture holds the greatest reduction potential, as nitrogen efficiency (fertilisation and feeding) must be increased and emissions of reactive nitrogen reduced. Deposition of reactive nitrogen to the environment can also be effectively reduced through energy savings and greater energy efficiency.