Nitrogen budget: a tool to validate information on nitrogen fluxes

Wilfried Winiwarter1

1 IIASA, Schlossplatz 1, A-2361 Laxenburg, Austria, www.iiasa.ac.at, [email protected]

Abstract

Reactive nitrogen compounds, released by anthropogenic activities, may take different pathways in the environment, not all of which are easily traceable. Nitrogen budgets allow using surrogate information for fluxes that otherwise cannot easily be measured or validation of flux quantities for which an independent second set of data can be made available. In order to reliably assess nitrogen budgets and to make them comparable, the harmonization of approaches is required. Such a harmonizing effort has been performed under the European “air quality” convention, the Convention on Long-Range Transboundary Air Pollution. Based on existing efforts to collect data on fluxes of nitrogen compounds, specifically in the framework of the convention, from national greenhouse gas inventories mandatory under UNFCCC, or in connection with European activities of EUROSTAT or OECD, a guidance document has been developed to allow assessing national nitrogen budgets. Eight individual “pools” have been identified that are considered the start- and endpoints of environmental fluxes. The guidance document allows fluxes between pools to be properly assigned and quantified and provides a framework for consistent nomenclature. This paper shows complete and partial applications of the concept, and demonstrates the advantages of harmonizing approaches. It takes available published budgets for several European and non-European countries, analyzes them for compatibility, and evaluates nitrogen budgets for their potential contribution to a sustainable development of agriculture and beyond agriculture. From the few available examples is can be shown that nitrogen budgets allow to identify missing information as well as to define areas of intervention into the nitrogen regime. Comparing over time shows trends, e.g. as a result of environmental legislation, comparing between countries displays national characteristics useful for benchmarking. Linking towards specific abatement, nitrogen budgets may help in attaining “planetary boundaries” for nitrogen.