Reactive nitrogen (Nr) includes the inorganic (NH3, NH4, NOx, HNO3, N2O, NO3) and organic forms (urea, amines, proteins, nucleic acids) that readily participate in various reactions of the global N cycle. Over the last half a century, anthropogenic perturbations of the natural N cycle have led to the increasing accumulation of inorganic Nr in the soil, water and air, intentionally through agriculture and unintentionally through fosill-fuel consumption and other activities, adversely affecting human health, biodiversity, environment and climate change.

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