Plant colonization of brownfield soil and post-washing sludge: effect of organic amendment and environmental conditions

This paper analyses the effects of substrate properties and environmental conditions on spontaneous vegetation of soil and sludges from a dismantled steel plant moderately polluted by heavy metals and polycyclic aro- matic hydrocarbons. Plant colonization was monitored in the presence or absence of acidic peat for 5 years both inside the degraded brownfield site and after transferral into a nearby Oak Park environment. Overall, 57 plant species grew healthily on the substrates, with peat enhancing plant growth in the unfavourable brownfield site. Most of the species were found in the park (91 %), showing plant colonization was mainly affected by the immediate environment rather than by substrate properties. Restricted metal uptake and tissue accumulation by selec- ted plants were measured, with only Daucus carota showing a higher ability to translocate metals to shoots (shoot/root metal concentration quotient [1 with peat). Phytostabilization with native plants represents an eco- nomically more realistic and cost-effective option than excavation, soil washing and sludge disposal, especially for vast industrial sites. Addition of organic matter and planting strategically selected vegetation islands could facilitate the spontaneous recovery of such highly degraded environments.