Influence of the Sea Rush Juncus maritimus on Metal Concentration and Speciation in Estuarine Sediment Colonized by the Plant

Abstract

Metal accumulation by Juncus maritimus and the role of this plant on the physical and chemical composition of sediments, from the Douro river estuary (NW Portugal), were investigated. The contents of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined (by atomic absorption spectrophotometry) in sediments, rhizosediments (those among plant roots and rhizomes), and different plant tissues (roots, rhizomes, leaves, and stems). Metal fractionation in sediments through sequential extraction was carried out and used for interpretation of sediment/J. maritimus interactions. Two estuarine sites with different characteristics were studied: site I displayed sandy sediment with lower organic matter and metals more weakly bound to it than site II sediment, which was muddy. At both sites, higher metal contents were observed in rhizosediments than in the surrounding sediment, but metals were more weakly bound to rhizosediment. Therefore, J. maritimus markedly influenced the sediments among its roots and rhizomes, changing metal distribution and speciation. Different patterns of both metal uptake and metal distribution among J. maritimus tissues were observed at the two sites. Plant bioaccumulation was only observed for Cd, Cu, and Zn, being similar for Cd atthe two sites and significantly higher for Cu and Zn (9 and 4 times higher, respectively) at site I. In conclusion, J. maritimus was shown to have potential for phytoextraction (or phytostabilization) of Cd, Cu, and Zn in estuarine environment. However, an eventual application of J. maritimus for this purpose will require a periodic removal of the plants together with their own rhizosediment.

The role of two Spartina species in phytostabilization and bioaccumulation of Co, Cr, and Ni in the Tinto–Odiel estuary (SW Spain)

“…Concentrations of Cr in plants vary widely according to tissue type and growth stage, and the pattern of Cr variation appears to be irregular (Mertz et al, 1974;Kabata-Pendias & Pendias, 2001). We found a high translocation of Cr from roots to shoots in both Spartina species, which concurs with various studies demonstrating that roots retain small quantities of Cr (Windham et al, 2003;Almeida et al, 2004). Luque et al (1999) found similar concentrations of Cr in S. densiflora and S. maritima at Odiel marshes.…”

Mobility of metals in salt marsh sediments colonised by Spartina maritima (Tagus estuary, Portugal)

“…Higher sedimentation rates in areas colonised by halophytes compared to unvegetated areas are likely to be related to the observed pattern in metal concentration (1 and 0.6 cm year -1 , respectively, at Corroios, according to Caçador et al (2004)). In addition, activity of roots liberates oxygen and organic matter to sediments, and thus it is able to modify characteristics as Eh, pH and microbial activity which will eventually modify metal retention capacity (Williams et al, 1994a;Doyle & Otte, 1997;Kamnev & van der Lelie, 2000;Almeida et al, 2004). Spartina maritima has a well-developed arenchyma and therefore presents the ability to oxidise the rhizosphere, being able to colonise anoxic environments.…”

“…Furthermore, speciation of Pb and Zn in sediments colonised by these two species has been found to be different, and such differences might be a result of both the type of colonising species and the location (own unpublished results). Studies made in several estuaries have shown that speciation of metals in salt marsh sediments depends greatly on local factors, such as sediment redox potential or grain size, in addition to metal nature or presence of roots (Allen et al, 1990;Caçador et al, 1996b;Mortimer & Rae, 2000;Otero et al, 2000;Sáenz et al, 2003;Almeida et al, 2004).…”

Hydrocarbon degradation potential of salt marsh plant–microorganisms associations

“…Estuaries are often considered sinks for contaminants, receiving important anthropogenic inputs from the upstream catchments and from metropolitan areas and industries located on or near those areas (Almeida et al 2004). Estuaries are dynamic, complex and unique systems that present both seasonal and spatial variability (Chapman and Wong 2001).…”