Morphological Response of Typha domingensis to an Industrial Effluent Containing Heavy Metals in a Constructed Wetland

Abstract

Typha domingensis became the dominant species after two years of operation of a wetland constructed for metallurgical effluent treatment. Therefore, the main purpose of this study was to investigate its response to tolerate the effluent and to maintain the contaminant removal efficiency of the constructed wetland. Plant, sediment and water at the inlet and outlet of the constructed wetland and in two natural wetlands were sampled. Metal concentration (Cr, Ni and Zn) and total phosphorus (TP) were significantly higher in tissues of the plants growing at the inlet in comparison with those of the outlet and natural wetlands. Even though chlorophyll concentration was sensitive to effluent toxicity, biomass and plant height at the inlet and outlet were significantly higher than those in the natural wetlands. The highest root and stele cross-sectional areas (CSA), number of vessels and biomass registered in inlet plants promoted the uptake, transport and accumulation of the contaminants in tissues. The modifications recorded accounted for the adaptability of T. domingensis to the conditions prevailing in the constructed wetland, which allowed this plant to become the dominant species and enabled the wetland to maintain a high contaminant retention capacity.