Work package numberWP2Lead BeneficiaryJustus Liebig University Giessen (JLU)
TitleNitrogen lateral and deposition fluxes  
Start Month1 (Feb 2020)End Month48 (Jan 2024)

WP2 syntheses the current knowledge on N contents in the terrestrial biosphere, the aquatic systems and the atmosphere, lateral N fluxes and deposition fluxes, at the local, regional and continental scale. N contents, including N gaseous compounds (NO, NH3, HNO3, N2O, N2), particulate and dissolved organic and inorganic nitrogen (PON, DON), N compounds in soil (in relation to C and P), in vegetation, and aquatic systems will be documented for natural, seminatural as well as anthropogenic systems.


The objectives of this work package are to

  • Provide a synthesis of the current knowledge on N stocks and lateral and deposition fluxes to identify gaps and uncertainties both in experimental and modelling studies
  • Quantify N content in compartments of the critical zone (biosphere – atmosphere – hydrosphere) in Africa at different time scale
  • Quantify N lateral fluxes between terrestrial and aquatic systems
  • Collect information on N deposition fluxes at the continental scale. WP2, in association with WP3 where terrestrial emissions fluxes will be studied, will help to provide essential knowledge on N stocks and flows, to give reliable information for model validation, and to quantify model accuracy on impact prediction. All the partners listed in this WP both European and African will work together to evaluate data and will jointly develop the interoperable platform proposed in WP5 for sharing all these information. Standard Operating Procedures (SOP), including guidelines on site selection (representativeness), on adequate instrumentation, on collection procedures, on analytical protocols, on quality assurance (QA) and quality control (QC) will also be developed in this WP.

Description of work and role of partners

Task 2.1: Literature review and study selection (Lead: Félix-Houphouët-Boigny University (FHBU))

In close cooperation with WP3, we will carry out a literature review and a synthesis of current knowledge on N stocks in soils, vegetation, water bodies and atmosphere and N flows between compartments (biosphere – atmosphere – hydrosphere) on various spatio-temporal scales. The related work under WP3 will focus more precisely on N flows in terrestrial systems. Evaluation of all reliable and available datasets will be performed through exchanges of information between all INSA participants, potentially owners of such data, via email/telecons, and during secondments. Toulouse III – Paul Sabatier University (UT3) – Laboratoire d’Aérologie (LA) and Laboratoire Geosciences Environnement Toulouse (GET) staff has long-term experiences in working in Africa and in establishing site, regional and networking activities especially in atmospheric chemistry, ecology and hydrology. UT3 Paul Sabatier has been active in all SSA regions for more than 25 years with strong collaborations with African research institutions in several countries. The expertise of UT3 Paul Sabatier staff, associated to the expertise of all the institutions involved in the WP2 will allow to cover all relevant fields from measurement to modelling and integration.

Task 2.2 : N contents in soil, vegetation, aquatic systems (ground water, rivers, lakes), atmosphere (Lead: Institut Sénégalais de Recherches Agricoles (ISRA))

Compilation of existing ground based observations from selected regions (West, Central, East and South Africa) based on long term monitoring and/or intensive campaigns will be realized in this task. This work will be done in association to an evaluation of satellite profile data and products derived to surface measurements. An evaluation of all ancillary data (climatic parameters, meteorological parameters, soil humidity and temperature, fertilizers use, agricultural practices, industrial and sewer effluents) will be done. The secondments supporting INSA, as well as the expertise of the Toulouse III – Paul Sabatier University described previously will provide the right expertise to evaluate if the observations of N stocks in the different compartments of the critical zone (atmosphere-biosphere hydrosphere) follow the international standards recommended by Global Atmospheric Watch (GAW) and by the European ACTRIS infrastructure. INSA will use the current infrastructure and procedures offered by WMO/GAW for reactive gas measurements and total atmospheric deposition as well as the Copernicus platform for land and atmosphere to initially facilitate access to data, and to involve the partner organizations in the data management. The data compilation will also consider the links with the WMO World Data Centers and other data centers. All the databases evaluation and validation performed in this task will be integrated in the interoperable platform (under work package 5)

A preliminary list of relevant resources includes:

Task 2.3 : Lateral fluxes between aquatic and terrestrial systems (Lead : Justus Liebig University Giessen (JLU))

This task will contribute to the database for lateral fluxes of nitrogen between aquatic and terrestrial systems to assist in management of nitrogen. The nitrogen database to address lateral fluxes between aquatic and terrestrial systems in the Sub-Saharan Africa is not adequately developed. There is an increase of transfer of nitrogen (and phosphorus) from terrestrial ecosystems to aquatic ones. This is linked, among other reasons, to clearing and poor agricultural practices leading to soil erosion and nitrogen leaching to the streams and rivers which had significantly affected lakes and rivers on the African continent. Those high rates of nitrogen and phosphorus evasion have resulted into declines in soil nutrients, poor crop productivity and deterioration of aquatic bodies. This phenomenon can also have an influence on the climate through N2O emitted to the atmosphere. Existing emissions of N2O from freshwater systems are estimated from emission factors modelled on N land deposition and are not actually based on in-situ data. Furthermore, the modelling of N2O emissions from aquatic systems is complicated by the fact that N2O is produced by both nitrification and denitrification, while denitrification can be complete and emit N2 depending of presence or absence of oxygen and in that case N2O is not necessarily emitted. Hence, in order to better constrain global emissions of N2O from aquatic systems, more estimates are needed, particular is areas where data are very scarce such as in Africa. In this task, we will use data collected in different African regions (Kenya particularly) and in a variety of aquatic systems typical of the African landscape such as brackish lagoons, rivers, reservoirs and natural lakes. Additional variables needed for the interpretation of N2O data will also be compiled such as dissolved oxygen, water temperature, and dissolved inorganic nutrients (NH4+, NO3-). UT3 Paul Sabatier and JLU have a great expertise in this kind of measurements and projects.

Task 2.4: Dry and wet deposition fluxes (gases, particles and rain chemistry) (Lead : Toulouse III – Paul Sabatier University (UT3))

This task will gather all existing ground based observations available for different African regions (West, Central, East and South) and African countries participating in this project. This WP will use gas and particle N datasets compiled in T 2.2 and will screen all data about rain N chemistry in Africa. INSA partners such as North West University in South Africa, Félix-Houphouët-Boigny University in Ivory Coast and Abomey-Calavi University in Benin are already part of international long-term deposition networking activities through the INDAAF network which is part of the European ACTRIS–FR program and as an official contributing network of the Global Atmospheric Watch (GAW) network of WMO. INDAAF researchers have contributed to the African chapter of the last deposition WMO/GAW assessment. East-African partners have developed a GEF UNEP project to document deposition in Equatorial Africa (EADN). In addition, we will add to these long-term database local or site studies on N deposition (and P if available). e.g. from three distinct forest types in DR Congo (UGENT-network). All the data will be merged into the best estimation of nitrogen deposition fluxes including wet and dry processes. Inferential modelling to estimate dry deposition fluxes will be performed using calculations of dry deposition velocities and N concentrations. This work package should help to document N deposition fluxes at a monthly, seasonal and annual scale and to build N deposition budget representation at regional scale of African ecosystems. Finally, this work should lead to a spatial distribution of N deposition fluxes at the continental scale using the REGCM and EMEP model. Further, an important objective of the long-term regional monitoring programs is to document changes in the atmospheric composition and test the effectiveness of environmental policies, and this work may demonstrate the usefulness of strengthening the international cooperation among regional measurement networks.

Description of deliverables

D2.1: Determination of temporal variations for N contents in soils, vegetation, atmosphere and aquatic systems (month 18, July 2021)

D2.2: Calculations of N wet and dry deposition fluxes (month 25, Feb 2022)

D2.3: Data compilation on N contents and lateral fluxes (month 43, Aug 2023)

D2.4: Report on N deposition fluxes (month 46, Nov 2023)

D2.5: Standard Operating Procedure (SOP) related to technical skills (month 46, Nov 2023)