Advances in nitrogen footprint research

As a result of anthropic activities such as fertilizer application and fuel burning, the amount of reactive nitrogen emitted into global eco-system has been increased yearly since the 19^th century industrial revolution. Reactive nitrogen emitted into global eco-system has resulted in serious environmental issues such as surface water eutrophication, groundwater pollution and stratospheric ozone depletion. Nitrogen footprint was put forward in the backdrop of increased severity of global reactive nitrogen pollution. Research on nitrogen footprint has theoretical and practical significance in evaluating the effect of anthropic activities on reactive nitrogen emission, regulating human life style and reducing anthropic reactive nitrogen emission. Although western scientists have increasingly focused attention on nitrogen footprint research in recent years, and a few literatures have been published on this discipline. On the contrary, research on nitrogen footprint is not deeply rooted in China’s scientific community. There are hardly any published literatures of nitrogen footprint by Chinese scientists. This paper therefore reviewed the definitions, calculating models, research advances/significance, and future research directions of nitrogen footprint. The review showed that future nitrogen footprint research hot-pots were improving/developing calculating models, determining relative weight of reactive nitrogen species, and assessing nitrogen footprints in heavy reactive nitrogen pollution regions/countries.