Using stable isotopes to trace the flow of nitrogen and the role of denitrification in a restored prairie wetland complex receiving wastewater effluent

Wetlands play a crucial role in reducing nitrogen concentrations in wastewater effluent before it is discharged into public waterways. This study aims to trace the inorganic nitrogen input from treated industrial wastewater effluent into the Frank Lake wetland complex in southern Alberta, Canada, its uptake and subsequent movement through the Little Bow River to the Twin Valley Reservoir by analyzing the stable isotope composition of nitrogen in sediment and leaf tissue samples of Typha latifolia and Schoenoplectus acutus. In addition, this study analyzes the magnitude of denitrification, which removes nitrogen in the wastewater effluent as water moves through the wetland, using nitrogen isotopic compositions of nitrate molecules in the water. The study identified significant nitrogen uptake and processing within Basins of Frank Lake wetland, primarily due to emergent aquatic vegetation uptake and phytoplankton assimilation leading to sediment deposition and denitrification. Although the wetland effectively processed nitrogen, downstream effects on the Little Bow River system were observed, as evidenced by increased δ15N levels in T. latifolia samples. The Twin Valley reservoir also showed elevated δ15N values, likely due to wastewater discharge from Nanton through Mosquito Creek. Moreover, there was a substantial reduction in nitrate levels in the wastewater effluent within Basin 1, with denitrification removing 27.6 % to 43.7 % of nitrates in June, 12.6 % to 17.0 % in July, and 8.4 % to 14.0 % in August 2023. The study offers valuable insights into the ecosystem service of nutrient uptake provided by the wetland complex.

Authors

• Palle Rankoth Gedara, Kasuni Tharushika Rankoth
• University of Lethbridge. Faculty of Arts and Science

• wetland ecology
• nutrient cycling
• nitrogen removal
• nitrogen cycling
• Frank Lake wetland complex
• wetlands
• Little Bow River
• plant bioindicators

Identifier

hdl:10133/6907

OAI identifier oai:identifier

oai:opus.uleth.ca:10133/6907