International audience | In a lysimeter set-up, compost addition to an industrial contaminated soil slightly reduced phytotoxicity to bean seedlings. The "Phytotoxicity Index" (on a scale from 1 to 4) decreased from 3.5 to 2.8. The same treatment also reduced metal accumulation in grasses: mean Zn, Cd and Pb concentrations decreased respectively from 623 to 135, from 6.2 to 1.3 and from 10.7 to < 6 mg kg(-1) dry weight. When combined with inorganic metal immobilizing amendments, compost had a beneficial effect on plant responses additional to the inorganic amendments alone. Best results were obtained when using compost (C) + cyclonic ashes (CA) + steel shots (SS). The "Phytotoxicity Index" decreased to 1.7, highest diversity of spontaneously colonizing plants occurred, and metal accumulation in grasses reduced to values for uncontaminated soils. Based on the first year evaluation, C + CA + SS showed to be an efficient treatment for amendment assisted phytostabilization of the contaminated Overpelt soil

Physicochemical and biological characterisation of different dredged sediment deposit sites in France

Zinc toxicity thresholds for reclamation plants are largely unknown. As a result, ecological risk assessments often rely on toxicity thresholds for agronomic species, which may differ from those of restoration species. Our objective was to provide Zn toxicity thresholds for forb species that are commonly used in reclamation activities. We used a greenhouse screening study where seedlings of yarrow (Achillea millefolium L.), Bigelow's tansyaster (Machaeranthera bigelovii (Gray) Greene var. bigelovii), blue flax (Linum perenne L. var. Appar), alfalfa (Medicago sativa L. var. Ladak), Palmer's penstemon (Penstemon palmeri Gray), and Rocky Mountain penstemon (Penstemon strictus Benth. var. Bandera) were grown in sand culture and exposed to increasing concentrations of Zn. Lethal concentrations (LC50 - substrate Zn concentration resulting in 50% mortality), effective concentrations (EC50 - substrate Zn concentration resulting in 50% biomass reduction), and phytotoxicity thresholds (PT50 - tissue Zn concentration resulting in 50% biomass reduction) were then determined. Phytotoxicity thresholds and effective concentrations for these reclamation species were relatively consistent between species. Our estimates of PT50-shoot for these species range from 1258 to 3214 mg Zn kg-¹ . Measures of EC50-plant for these restoration forbs ranged from 82 to 214 mg Zn L-¹ . These thresholds might be more useful for risk assessors working on reclamation sites than those based on non-reclamation species that are widely used.