Modelling contamination in an urban canal sediment: Some preliminary results from a phytoremediation project

Sediments in a derelict section of canal in a former industrial region of North-West England contain a wide range of elevated contaminants including Cu, Zn, Ni, As, Pb, Cd, Cr, mineral oils, TPHs, PAHs and sulphides. Associated costs of disposal have been a constraint to restoration of the canal, which has remained unused for navigation for 50 years or more. On-site phytoremediation is being used in the current project to investigate whether a healthy environment can be restored without extensive removal of the sediment from the site. A raised platform of dredged sediment has been created within the partially drained canal. As the sediment dries and becomes aerated, metal availability was markedly altered and volatilisation rates of organics appeared to increase. Decreasing sulphide/sulphate ratios, lowered pH and altered Fe mobility had differing effects on trace elements. Repeated wetting and drying mobilised a substantial proportion. The project is comprehensively modelling these processes, and aims to demonstrate that metals can be rendered immobile and non-hazardous in soils and biomass whilst plant roots and developing biota optimise conditions for the natural attenuation of organics.