Phytoremediation of two types of sediment contaminated with Zn by Schoenoplectus americanus

Abstract

The effect of different sediments on growth, Zn uptake, Zn plant distribution, and morphometric variables of Schoenoplectus americanus were investigated under controlled conditions. Two types of sediments were assayed: from a large natural levee (LS) and alluvial sediments (AS), the former with lower organic matter (OM) and nutrients content than AS, without and with added Zn (2500 μg Zn/g air-dry sediment). Zinc partition in sediment was determined. Increases in water conductivity and Zn concentrations in water and sediments were observed in artificially contaminated treatments. Plants showed a lower aboveground growth rate, height, and width of shoots, and a higher Zn concentration in shoots and rhizomes. In the contaminated treatments, AS treatment showed lower Zn concentration in water and higher Zn concentration in sediments (total, exchangeable, and OM fractions) than LS treatment, due to Zn displacement from floodwater to sediments. The presence of a high level of OM and nutrients also increased aboveground biomass growth, whereas it decreased Zn concentration in shoots. Although the translocation factor increased with Zn addition, it was lower in AS treatment. Sediments of AS treatments are a suitable environment for growth of S. americanus, which partially compensates the toxic effects of Zn. Our results provide an encouraging basis for planning larger scale experiments to test the role of OM and nutrients in improving phytoremediation.