1. Subject Description

Globally, agriculture is responsible for 10 to 12% of total anthropogenic greenhouse gas (GHG) emissions, mainly in the form of nitrous oxide (N2O) and methane (CH4) (Smith et al., 2007; Butterbach-Bahl et al., 2011). The farming sector also plays a central role in air pollution. Indeed, it contributes significantly to ammonia (NH3) emissions (90% globally) (Lelieveld et al., 2015) and nitrogen oxides (NO). These emissions affect tropospheric chemistry, with ammonia being a precursor of fine atmospheric particles (Backes et al., 2016; Gu et al., 2014).
Agro-ecosystem models simulate biogeochemical processes in the soil/plant system, such as the immobilization of carbon (C) and nitrogen (N) in the soil, the mineralization of organic matter, plant photosynthesis or even respiration, in order to distribute C and N in the aboveground biomass and in the organic matter of the soil. Among these models, we can cite the CERES-EGC (Crop-Environment REsources Synthesis, Gabrielle et al. 2006) and STICS (Multidisciplinary Simulator for Standard Crops, Brisson et al. 2003) models. The Syst'N® tool, which is based on descriptions close to those of agro-ecosystem models, was designed to allow the evaluation and diagnosis of nitrogen losses in cropping systems on a rotation scale.
Different modeling concepts have been developed to account for the physical and physicochemical processes controlling ammonia emissions from synthetic or organic fertilizers after fertilization and to simulate their dynamics (Sommer et al., 2003; Montes et al., 2009). Among these models, the UMR EcoSys has developed the Volt'Air process based model (Génermont and Cellier, 1997; Le Cadre, 2004; Garcia et al., 2012) which simulates the volatilization of ammonia after spreading on bare soil of organic or synthetic fertilizers.
Simple formulations taken from the literature and the expertise in the UMR EcoSys were introduced into the CERES-EGC and STICS models, as well as into the Syst’N® tool, in order to simulate NH3 emissions. These formalisms have not been evaluated in comparison to field measurements in different agro-pedo-climatic conditions. A large number of datasets were acquired in the EcoSys UMR through field experiments with different agricultural practices as weel as in semi-controlled conditions with ventilation tunnels, or in fully controlled conditions.
The objective of this internship is to compare the ammonia emissions modules of the CERES-EGC, STICS and Syst'N® models, to compare them to measured data as well as the Volt'Air model, and to suggest ways to for improvement.

Méthodology

One of the trainee's first tasks will be to understand the determinants of NH3 emissions and the different ways of taking them into account in modeling and more particularly in the CERES-EGC and STICS models. She/he will then participate in the development and completion of the database currently being constructed. She/he will parameterize the two models on the sites and types of fertilizers selected. She/he will develop (use) R scripts to compare simulation outputs to data. She/he will validate the data and ensure the homogeneity of the units. A final step will consist of proposing options for improvement (taking into account pH, availability of NH4+ in the first layer of soil or fertilizer, parameterization of turbulent exchanges above the surface, etc.)

Required Skills
- Knowledge of biosphere-atmosphere interactions
- Ability to do understand a model and its equations
- Affinity for modeling and data processing

Acquired Skills
- Knowledge on NH3 exchange between agricultural surfaces and the atmosphere
- R-and Fortran coding
- Data analysis
- Scientific communication

2. Specificities

Place of work: UMR ECOSYS on the Campus Agro Paris-Saclay in Palaiseau
Working conditions :
Conventional intern salary for public sector approx. €600/month
Coverage of 75% of the public transport subscription
Access to the canteen at the student rate
Duration: 6 months, starting date possible as of February 2024

3. Supervisors

Raia Silvia MASSAD raia-silvia.massad@inrae.fr  Tel : 01 89 10 07 07 UMR EcoSys
Sophie GENERMONT sophie.genermont@inrae.fr  Tel : 01 89 10 07 06 UMR EcoSys