Centre Européen
de Recherche et d'Enseignement
des Géosciences de l'Environnement

Zoom on ... "Changing Soils"

Soils: a resource to be protected

As much as air and water, soils must be considered as a resource to be protected: they support our food production, filter fresh water or mitigate climate change by storing carbon. But the services provided by soils are threatened by the uses we make of them: accelerated erosion, pollution, overgrazing, loss of organic matter, salinization, artificialization or even a decrease in biodiversity are all examples that threaten the "soil" resource. The team's work on soils, shared in part with the Climate research group, focuses on 4 main objectives:

Control the bio-geochemical cycles in soils

Our work aims to understand the origin, behavior and impact of metallic, (nano)particulate, (in)organic and microbial pollutants in soil and the associated risks. We develop multidisciplinary approaches - experimental (mesocosms, bioreactors), analytical (coupling between spectroscopy and isotopy, genotoxicology methods) and field (long-term tests) - in order to (i) understand the exposure pathways of organisms to pollutants and the biophysical-chemical mechanisms of toxicity, (ii) to study the biodegradation of various materials, the potential release of contaminants and their transfer to organisms and (iii) to evaluate the impact of agricultural recycling of organic wastes on the contamination of the food chain. In addition, we conduct research on issues related to agriculture and soils (impact of crops on bioavailable Si reserves, role of phytoliths in the development of plants under environmental stress).

Pedogenesis: predicting 2100

The work on soil pedogenesis under climatic and anthropic constraints concerns simple changes of use up to artificialization. The approaches aim at quantifying the evolutions and the kinetics: by field or experimental pedologies, modeling, isotopic tracings. The team reinforces the mechanistic and statistical numerical approaches. The objective is to predict the evolution of soils in the medium and long term for spatial scales ranging from profile to world. Projects anchored in regional issues are implemented, in particular on highly anthropized, urban and peri-urban soils, which represent very important issues on the scale of changing territories. These soils have specific dynamics that need to be identified (typology, physico-chemical impacts, pedogenesis kinetics, potential for use or restoration) in order to take them into account in sustainable development.

Storing C in the soils

We analyze and model C dynamics along the soil profile, in particular to highlight and quantify the effect of organo-mineral interaction on C stabilization, vertical transport processes, the impact of climate change (precipitation), change of use and practices on ecosystem C. Isotopic analysis of specific compounds and organo-mineral fractions associated with 3D localization analysis at nano-scale are developed. The group has a recognized expertise in the quantification of soil organic C turnover by natural isotopic tracings (13C and 14C), at time scales from millennium to year.

Photo credit: Jérôme Balesdent, 2018. Age distribution of C 

Managing the soil heritage

Soil plays a major role in the economic and social development of territories. As a support for human activities, soils are first and foremost a substrate, a surface on which societies spread out and organize themselves (soil-space). It is also and above all a resource with qualities and properties. In 2006, the European Commission stated in its Thematic Strategy for Soil Protection that the functions performed by soil "must be protected because of their socio-economic and environmental importance" (COM, 2006). Appropriate soil management allows these functions to be maintained or even restored. However, in many countries, the scale of management and planning of land use is that of the municipalities. In France, these documents are drawn up in compliance with the laws relating to urban planning and risk prevention, and in accordance with the guidelines set out in other regulatory documents drawn up at a higher territorial level (SCOT, Master Plan, SDAGE, Risk Prevention Plan, etc.). This raises the question of land use planning, i.e., the choices and regulations regarding occupation and possible uses in urban planning documents, as well as the question of how to take into account soil quality in the development of these choices and regulations. Our work has shown that it is possible and accepted by local actors to integrate information on soil quality into a PLU in the form of a multipurpose use index. This research is conducted in collaboration with institutional partners (Aix-Marseille Provence Metropolis, City of Marseille, OHM-L and BMP, CEREMA.....) and AMU laboratories (ESPACE, IUAR).