Nitrogen balances in urban areas: purpose and potentials

While urban improvements most strongly characterize ongoing changes in the humanenvironment interaction, their influences on the nitrogen cycle so far have received limited attention. Here we develop a mass balance approach, consistent with available literature and with data collection for international reporting of agro-environmental data, and specifically address the role of cities in environmental degradation related to nitrogen compounds. We note that the urban environment not only features high temperature combustion triggering atmospheric emissions of NOx, or wastewater issues due to high population density, but periurban agriculture producing high-value goods is particularly wasteful in its use of nitrogen as nutrient.

Nitrogen pollution is one of the most evident examples of human influence on the global environment. With an anthropogenic contribution at a similar level as the natural nitrogen cycle, environmental reactive nitrogen has been recognized one of the issues exceeding planetary boundaries (Steffen et al., 2015). Nitrogen largely is an agricultural problem, with excess application as a plant nutrient representing the key release process. On the global scale, urbanization constitutes the key driver of anthropogenic impacts. Therefore here we investigate the urban aspects of the human-induced nitrogen cycle.