Distribution of high Zn concentration in unvegetated and Typha domingensis vegetated sediments.

Abstract

A greenhouse experiment was conducted to determine if the presence of Typha domingensis affects the accumulation and speciation of high concentrations of Zn in sediments of aquatic systems. Reactors containing sediment and 2 plants of T. domingensis were disposed by triplicate. The treatments were: 1) 100 mg L-1 Zn (Zn100); 2) 500 mg L-1 Zn (Zn500) and 3) Control, without Zn. The same treatments without plants were disposed. The experiment lasted 30 days. Zn was efficiently removed from water in all treatments (greater than 75%). In Zn500 treatments, Zn removal was significantly high in vegetated reactors. Zn accumulation was significantly high in the superficial sediment layer (0-3 cm). T. domingensis influenced Zn accumulation and its distribution in sediments. The unvegetated sediment accumulated higher Zn concentrations than vegetated sediments. Zn was accumulated in less available fractions in unvegetated than vegetated sediments. Submerged parts of leaves accumulated higher Zn concentration than the other plant organs. Plants did not show toxic symptoms, so it could be assumed that they would continue taking up Zn. In the case of a dump of high concentrations of Zn, constructed wetlands could retain it, minimizing environmental impact. Further investigation is needed to evaluate the role of plants in the sustainability of Zn retention in constructed wetlands.