Trace metal concentrations in the sediments and plants of the Danube Delta, Romania

Wetlands systems generally are considered as filters, retaining allochthonous metals that can have toxic effects on biota. We investigated patterns of spatial variability in trace metal concentrations in sediments and tissues of Phragmites australis in the marshes of the Danube Delta, Romania in 1993 and 1994. Mean concentrations (+/- s.e.) of Ni, Cr, and Pb in roots were 10.0 +/- 0.7, 3.7 +/- 0.2, and 11.3 +/- 0.5 mu g g(-1) dry we, respectively, and in leaves were 0.3 +/- 0.1, 0.1 +/- 0.0, 0.2 +/- 0.0 mu g g(-1) dry wt, respectively. Mean concentrations (+/- s.e.) of Ni, Cr, Zn, and Cu extracted (0.5 M HCl) from sediments were 16.4 +/- 0.8, 3.0 +/- 0.2, 45.4 +/- 1.7, and 29.2 +/- 2.3 mu g g(-1) dry wt, respectively. Sediment metal concentrations decreased significantly (p < 0.01) with distance from the Delta origin, but concentrations in roots and sediments did not vary with distance into the marsh from lake edges nor with distance from main river channels in the Delta. Concentrations of extractable metals from marsh sediments were not correlated to concentrations in roots, suggesting that factors other than labile concentrations in sediments control metal uptake and storage in roots.