Phytoremediation of contaminated sediments: evaluation of agronomic properties and risk assessment

Abstract

This study evaluates the possibility of reusing marine sediments in land management. The sediments, dredged from Livorno port (Italy), had previously been phytotreated, using a salt-tolerant plant cover and earthworms, with the aim of reducing the salt level and improving the texture and microbiology. In this study, sediments were investigated in order to: (1) test their capability to be used as a revitalised soil-like substrate (techno-soil), and (2) assess the human exposure risks associated with sediment management. Results obtained after 6 months of experiments performed with biological indicators composed of an association of graminae grass (Paspalum vaginatum), legumes (Trifolium alexandrinum) and earthworms (Eisenia foetida), showed that the substrate behaves like a natural soil capable of supporting biological life (total N=0.2%; total P=0.7%; EC=1.5 mS·cm ⁻¹; β−glucosidase=20 μ g PNP·g *h ⁻¹). It was also found that plants accumulate small amounts of heavy metals in shoot tissues (120 mg Zn·kg⁻¹; 25 mg Cu·kg⁻¹). In detail, risk analysis was performed considering: (1) sediment storage in a sealed disposal basin inside the Livorno port area, and (2) off-site phyto-remediation. The maximum hazard index was found for workers inside the port area, with values of 1.7 and 25 for dermal contact and vapour inhalation risks, respectively.

Keywords:

• marine sediments
• heavy metals
• phytoremediation
• risk assessment

Acknowledgements

The study was funded by MIUR (PRIN 06): ‘Definition of a protocol on an experimental basis for the setup of a methodology of phytoremediation of soils and sediments with contaminants of different nature’. The authors thank Eng. Arianna Orsucci for her help in the production of the work.