Saturday, 15 July 2006

Ecological assessment of a constructed soil on degraded sites.

Geoffroy Séré1, Stéphanie Ouvrard1, Christophe Schwartz1, Jean-Christophe Renat2, and Jean Louis Morel1. (1) INPL(ENSAIA)/INRA, Laboratoire Sols et Environnement, BP 172, 2 avenue de la forêt de Haye, F-54505 Vandoeuvre les Nancy Cédex, France, (2) TVD-Groupe PE, Centre d'Affaires, ZI Clairs Chênes, F-54230 Chavigny, France

This paper presents an emerging process to manage altered soils. The proposed solution deals with the main issues concerning derelict lands reclamation: soil functioning and fertility, biological diversity and protection of the water resources.

From an ecological point of view, these degraded sites (e.g. industrial brownfields, landfills, roadsides or ski runs) are severely disturbed zones, presenting an ecosystem balance that needs to be restored. The main challenges of degraded sites reclamation include the re-initiation of carbon and nutrient cycling, the establishment of a sustainable plant cover (Bradshaw, 1983) and the limitation of the transfer of pollutants to the environment.

The process of soil construction for the reclamation of degraded sites is based on the recycling of wastes and by products, such as compost, paper sludge or treated industrial soil. These technic materials are used to construct a new soil (Technosol) over in situ brownfield substrates. They are associated and stacked in layers to form new horizons and reproduce the basic soil functions.

Our work first aims at evaluating the efficiency and sustainability of the soil construction, considering the global functioning of the recreated ecosystem. Another major objective is to assess the environmental impacts of the process as far as soil and water conservation and biological activity are concerned.

The project relies on both in situ pilot scale application and lab-scale experiments. The field experimental set-up consists in three lysimetric plots (10 x 10 m) that enable the collecting and analysing of the plants, the rainwater, the leaching water and soil samples. At the laboratory, columns experiments, under controlled conditions, have been realised to precise the mechanisms involved and to simulate the constructed soil evolution on a longer period of time. Pollutants are analysed in all matrix and ecotoxicological tests (Microtox®) are conducted.

The data concerning the major cycling, the soils properties and reactivity and the development of plants indicate a re-initiation of the ecosystem equilibrium. On the other hand the global balance of the system, as well as the results of the global ecotoxicological effects show that the implementation of the wastes in this process has no major environmental drawbacks.

Acknowledgements: This project is supported by the GISFI program and was founded by the Etat Français (ANRT), Région Lorraine (CPER), ADEME, EPFL and Bail Industrie.

Bradshaw A.D., 1983, The reconstruction of ecosystems, Journal of Applied Ecology, vol. 20, p 1-17

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