Growing Salix spp. on heavy metal contaminated sediment (Oskarshamn, Sweden) as a joint phytoremediation and circular economy approach

Abstract

The sediments of rivers or harbours have always been considered sinks for numerous heavy metals, pesticides, chemicals and contaminants of anthropogenic origin. The eco-friendly management of contaminated sediment have received attention due to their large-scale presence in harbour areas. Application of bioenergy crop species, such as Salix spp., have shown a strong potential for reducing heavy metals from the contaminated sediment. The aim of this study was to investigate the application of Salix spp. on contaminated dredged sediment and heavy metal accumulation and translocation patterns in different parts of plants. Two Salix cultivars (Wilhelm and Ester; commercially available in Sweden) were cultivated in contaminated sediment for 5 weeks in a field setting. Heavy metals (Cd, Cu, Pb, Ni and Zn) content in different plant parts (root, cutting, shoot and leaves) were analysed by using atomic absorption spectrophotometer (AAS). The result indicated that the root biomass production was negatively affected for both cultivars due to the contaminated sediment medium, even though no morphological symptoms were present. Both Cd and Cu net accumulation were found to be significantly higher in Ester cultivars. The low translocation of heavy metals in Salix spp. hints that accumulated heavy metals are stored in the root parts. Low translocation of heavy metals from contaminated sediments gives a strong potential for using a growth medium to utilize phosphorus (P) in the sediment from a circular economy and bioeconomy perspective.