S1: St Médard d’Eyrans (Gironde, FR)


Site “S-1”, Location: St Médard d’Eyrans 44°43.353′ N, 000°30.938′ W

Brief description:

This wood preservation site (formerly 10 ha) has been used for over a century to preserve and store timbers, posts, and utility poles. The industrial facility dates back to 1846. Soil investigation revealed contamination of topsoils by mainly Cu and PAHs. It represents now a phytomanagement experimental site.

In this site, INRA aims to implement the phytomanagement of contaminated soils meaning the long term combination of profitable crop production with gentle remediation options leading gradually to the reduction of pollutant linkages due to contaminant excess and the restoration of biological functions and ecosystem services. In this regard, the purpose is to take advantage of the inter- and intra-specific plant diversity and to investigate various plant assemblies able to initiate trajectories leading to sustainable, resilient ecosystem, to produce a plant biomass usable for the Bioeconomy and to remediate/enhance biological functions in line with associated ecosystem services.

In the last years, several plant species have been tested including the addition of soil amendments to promote growing. The tree species (either mycorrhized or not) tested include poplar (Populus nigra L.), willows (Salix caprea L and Salix viminalis L.) Scots pine (Pinus sylvestris), and false indigo bush (Amorpha fruticosa L.), among others. The main purpose is to produce a woody biomass, to phytostabilise Cu, to rhizodegrade the PAHs and to enhance the biological functions of soils. Apart from this, biotic interactions, notably facilitation (intercropping with alfalfa) is also investigated within the PhytoSUDOE project.
Apart from this, trials with grasses are being also carried out (sometimes in rotation with tobacco and sunflower); the species tested include Miscanthus spp., Chrysopogon zizanioides (vetiver), Agrostis capillaris, A. delicatula, A. gigantea, Dactylis glomerata, Deschampsia caespitosa, Sporobolus indicus, Vulpia myuros and Festuca pratensis.

Finally, based on Miscanthus’ capacity to sequestrate inorganic contaminants into the root system and to induce dissipation of persistent organic contaminants in soil, these plant species are favorable for phytostabilization and rhizodegradation. Among Miscanthus species, the noninvasive hybrid Miscanthus x giganteus, with a high lignocellulosic content, is a promising biomass crop for the bioeconomy, notably the biorefinery and bioenergy industries.

New research activities are focusing on soil amendment (e.g. biochar), intercropping and winter crops to enhance the beneficial effects from the phytomanagement