Reactive nitrogen at the CLimate, Energy, Agriculture, water, and health Nexus (ReCLEAN)

Nitrogen (N), the most abundant element in our atmosphere, is important to all life on Earth. However, several N species, referred to as reactive nitrogen (Nr), cause major environmental issues impacting climate, air quality, ecosystem and human health.

Fossil fuel combustion for energy production and agricultural activities emit substantial amounts of Nr in form of nitrogen oxides (NOx) and ammonia (NH3) to the atmosphere. Dry and wet deposition of Nr, along with N applications for agricultural practices, result in excess N inputs to ecosystems in Switzerland, with multiple interconnected adverse effects. These environmental impacts include loss of biodiversity, increased vulnerability of ecosystems to extreme events, widespread nitrate (NO3-) exceedances in groundwater, or enhanced formation of the greenhouse gas N2O.

Decarbonization of energy production will reduce NOx emissions from fossil fuels but increase NOx and NH3 emissions from the combustion of biofuels or biomass. In addition, production of biofuels will increase the demand for chemical fertilizers. At the same time, the globally rising per capita consumption and urbanization accelerate N pollution to atmospheric and aquatic systems in many regions of the world, including Switzerland.

The N cycle in atmospheric, terrestrial and aquatic environments is complex. How the energy transition will impact these systems and their interconnections is only poorly understood. Until now, researchers have mainly focused on individual compartments, thereby largely ignoring how one compartment impacts the other. Only a truly collaborative effort will allow for addressing the complexity of nitrogen deposition impacts on Switzerland and beyond.

Aim of ReCLEAN

The Joint Initiative ReCLEAN ranges from basic research to policy development. The aim is to achieve a holistic understanding and quantification of nitrogen fluxes across and within environmental compartments. This will make it possible to predict the effects of energy transition and environmental changes and provide sensitivity studies regarding future policies in Switzerland.

Expected outputs and outcomes

ReCLEAN will provide a spatially-resolved multi-compartmental modelling framework that can be used for comprehensive policy assessments. This Joint Initiative will also develop an observational supersite for nitrogen fluxes among all compartments that will complement the modelling activities. The project will provide critical information on Nr cycling and fluxes in and across environmental compartments, their associated risks to air and water quality, and ecosystems and human health, and how these are impacted by future changes in climate & energy policies and agricultural management. The output from this multidisciplinary approach will allow designing policies in energy, air and water quality, agriculture, and forestry to align toward beneficial sustainable outcomes for the N budget in Switzerland.