Suitability of Totora (Schoenoplectus californicus (C.A. Mey.) Soják) for Its Use in Constructed Wetlands in Areas Polluted with Heavy Metals

Juan Blanco

doi:10.3390/su11010019

Abstract

Schoenoplectus californicus subsp. tatora (totora) is an endemic plant from wetlands in South America’s Altiplano region. In the endorheic Titicaca-Desaguadero-Poopó-Salar de Coipasa system (TDPS), totora can be found along rivers, lakes, and shallow ponds. Lake Uru-Uru is a minor lake placed upstream of Lake Poopó, and it gets water inflows from the Desaguadero River, the city of Oruro and several mining and metallurgic complexes. Polluted waters from these origins, together with natural high salinity and high presence of As and Pb, make Lake Uru-Uru an ideal location to search for plant species suitable to be used in constructed and restored wetlands under pollution stress, particularly in systems with high pH and salty waters. To test if totora could meet such requirements, healthy plants were collected at two sites in Lake Uru-Uru with different exposure to polluted inflows. Chemical composition of different organs (leaves, rhizomes and roots) were compared. Results indicated totora’s capacity to withstand high concentrations of a cocktail of multiple pollutants and heavy metals. Particularly, this research showed totora as a multi-hyperaccumulator (concentrations in shoots higher than 1000 mg kg−1) for As, Fe and Ni. These results, combined with totora’s intrinsic high rates of biomass production, slow decomposition rates and its value as raw material for local craftwork and industrial uses, support the recommendation to use totora in constructed or restored wetlands, particularly in sites polluted with heavy metals, and in waters with high salinity.

Highlights

Wetlands are one of the most productive ecosystems on Earth, usually containing complex trophic webs and high biodiversity
Plants used in wetlands constructed for wastewater treatment should, have the capacity to grow in polluted sites, and even to be harvested as a way to remove pollutants stored in plant biomass
The particular objectives of this research were: 1) to provide the most detailed chemical composition of totora organs to date that could be used as a benchmark for future work; and 2) to test if totora is suitable for its use in construction or restoration of polluted wetlands, by testing if it can withstand significant differences in chemical composition in polluted sites compared to non-polluted sites

Summary

Introduction

Wetlands are one of the most productive ecosystems on Earth, usually containing complex trophic webs and high biodiversity. The situation is becoming worse as the effects of environmentally unfriendly activities, population increase, and urbanization are combined with a tradition of unsustainable management practices in wetlands [2,3]. In both developed and developing countries, the use of wetlands as disposal areas for untreated wastewater is troublesome. Plants ideal for such purposes should possess an intrinsic capacity to tolerate heavy metals and metalloids, concentrate them in harvestable aerial tissues, have high rates of biomass production, adsorb pollutants on the root surface, develop extensive and deep root systems, have wide distribution ranges allowing growth in many habitats, and should be easy to cultivate and harvest [4]

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