Site “S-2”, Location: St Médard d’Eyrans 44°43.353′ N, 000°30.938′ W
The Parc aux Angéliques is part of the Chaban-delmas brownfield (a former harbor dock). From October 2009 to December 2012, it was used as a repository of material stocks and machinery required for the bridge construction. The Bordeaux city decided to convert it into an urban park. The main contaminants are Zn, Cd, Cu, As, Pb, Ni and PAHs. Such soil contamination corresponds to the former industrial and harbor activities located on the Garonne riverbanks.
The Chaban-Delmas field trial was firstly divided into 18 plots (50×50 m) in June 2013 and then subdivided into 72 subplots (25×25 m) in November 2013. Among the 18 plots, four plots were colonized before the site development by a plant community dominated by herbaceous species, which was not mechanically removed during the bridge construction. In contrast, the vegetation on the remaining 14 plots was removed when work began and plot surface turned into a bare soil. Among these 14 plots, 10 were sowed in spring 2013 with alfalfa (Medicago sativa) while four plots remained unsowed. In March 2015, black poplar (Populus nigra L.) (from a native collection of the SW France) were transplanted on site.
Alfalfa develops well, initiating a healthy plant cover, with no exposure of herbivores and insects to contaminants, which diversifies over time. The structural and functional diversities of plant and soil microbial communities are assessed. The diversity of the soil mesofauna is also studied. The efficiency of other plant assemblies is tested in an off-site pot experiment.