Seasonal variation of Zn, Ph, Cu and Cd concentrations in the root-sediment system of Spartina maritima and Halimione portulacoides from Tagus estuary salt marshes

Concentrations of Zn, Pb, Cu and Cd have been determined in leaves, stems a nd roots of Spartina maritima Bad Halimione portulacoides from the Tagus es tuary salt mash (Corroios) and in the sediments between their roots. Biolog ical materials and sediments were sampled every 2 months, between July 1991 and July 1992. Root biomass increased from July to September and from Janu ary to March. The greatest metal concentrations occurred in the roots, with lowest levels in January and increasing levels during the growth periods. Zn, Pb and Cu in sediments exhibited a corresponding change in concentratio ns, reaching maximum in January and subsequently decreasing in spring. The ratios between metal concentrations in the root and in sediments were highe r for H. portulacoides when compared to S. maritima, whose roots are surrou nded by a more acidic and reduced sediment environment. It was concluded, t herefore, that H. portulacoides is a more effective accumulator of metals t han S. maritima, and both root-sediment systems exhibited a seasonal variat ion of metal concentrations. (C) 2000 Elsevier Science Ltd. All rights rese rved.