Bittersweet nature of nitrogen calls for better management practices

Nearly 80 per cent of the air we breathe is nitrogen, a harmless inert gas. However, nitrogen also combines with other atoms to form chemical compounds—known as “reactive nitrogen” or “fixed nitrogen” (Nr)—that are essential for life on Earth but, at high concentrations, also hugely damaging to the environment. 

“Altogether, humans are producing a cocktail of reactive nitrogen that threatens health, climate and ecosystems, making nitrogen one of the most important pollution issues facing humanity,” says UN Environment’s 2019 Frontiers Report. “Yet the scale of the problem remains largely unknown and unacknowledged outside scientific circles.”

There are four main types of reactive nitrogen, with differing benefits and environmental impacts:

Ammonia (NH₃) is found in manure, urine, fertilizers, and burning biomass. It’s the foundation for amino acids, protein and enzymes. In high concentrations however, it can cause algal blooms in lakes and forms particulate matter in the air which affects health and impacts terrestrial ecosystems such as peatlands and forests.

Nitrates (NO₃) are widely used as fertilizers and in explosives. We would produce only about half of our food without the use of fertilizers such as nitrogen and phosphorus. However, their accumulation in the environment can be toxic for life on Earth. Since they are the most water soluble of all salts, they are essential to the nitrogen cycle and a key source of nitrate pollution. Nitrates have been found in wastewater, agricultural runoff and in the atmospheric oxidation of NO_x.

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