Northern wild rice (Zizania palustris L.) as a phytoremediation species in eutrophic wetlands - investigation of root-sediment interactions

Abstract

The causes of anthropogenic eutrophication in water bodies are multi-faceted and multigenerational, presenting an ever increasing need for effective and sustainable solutions.Phytoremediation presents a cost-effective strategy to improve water body nutrient retention and removal, contributing to eutrophication mitigation efforts. This thesis examines the potential for northern wild rice (Zizania palustris L.) to be used as a phytoremediation species in eutrophic wetlands. An investigation into root-sediment interactions was undertaken to determine how northern wild rice affects water and sediment pore water chemistry. Northern wild rice growth was found to alter sediment pore water chemistry, contributing directly to nutrient retention during the summer growing season through nutrient assimilation in its tissues, and indirectly through increasing pore water Fe and Mn in the fall. The majority of P and N within the plant was found to be contained in the stems and leaves (44-53%), followed by the inflorescence (22-28%). Harvesting northern wild rice vegetation (including the seeds) at the end of the growing season would present a permanent nutrient removal mechanism. Substantial iron plaque forms on the roots of northern wild rice, visible as an orangebrown coating that ranges structurally from <1 μm to 14 μm thick. Iron plaques were found to be composed mainly of Fe, O, Al and K, with Fe found within and on root epidermal cells. P was not found to be associated with iron root plaques. With proper harvesting and management techniques, northern wild rice grown in eutrophic water bodies could present a viable phytoremediation method for nutrient removal.