Unravelling Nitrogen and Carbon Transformations in Constructed Wetlands Using Stable Isotope Tracers
Investigator:Dirk Erler, Bradley Eyre, Leigh Davison
Funding: ARC Linkage
Broad Objective
This project aims to improve our understanding of the nutrient transfer mechanisms that operate in constructed wetlands (CW's). This understanding will lead to better design and management of CW's, ultimately helping to improve the water quality in our waterways.
Specific Objective:
We aim to use stable isotope tracers to quantify the major processes regulating carbon and nitrogen in CW's used to remediate sewage treatment plant (STP) effluent.
Background:
Nutrient discharge from sewage treatment plants is of major environmental concern worldwide. STP discharge into waterways can lead to persistent eutrophication and therefore loss of recreational and commercial value. Constructed wetlands (CW's) can efficiently remove nutrients from an effluent stream and are becoming increasingly popular as a tertiary treatment option for STP's.
The removal and transformation of nutrients in constructed wetlands occur through a complex range of chemical, biological and physical interactions between water, plants, macro-invertebrates, micro-organisms, sediments, substrate, and the atmosphere. Despite this inherent complexity, the majority of constructed wetland research to date has adopted a simplistic "black box" approach, focusing on wastewater inflows and outflows, with little insight being gained into the actual processes and pathways responsible for nutrient cycling and removal. Thus, information on the relative rates and interdependency of component pollutant removal processes occurring within constructed wetlands is needed to improve performance predictions and design.The relatively new approach of whole system additions of stable isotope has significantly advanced our understanding of nutrient cycling in rivers, estuaries, salt marshes, and mangroves. The technique involves the addition of a suitable isotope (usually in ionic form) at an appropriate concentration to the inflow water of a particular aquatic ecosystem. The fate of the nutrients can then be tracked as they spiral through the ecosystem. Whole system isotope addition allows ecosystems to be quantified in terms of nutrient transformation, uptake and turnover rates. In addition to whole system additions, stable isotopes can be used for smaller scale incubations to quantify specific nutrient transfer processes in CW's. Together the 2 techniques offer a powerful method of studying ecosystem processes.
Publications:
Erler, D. V., Tait, D., Eyre, B. D. and Bingham, M. 2011. Observations of nitrogen and phosphorus biogeochemistry in a surface flow constructed wetland. Science of the Total Environment (in press). JIF= 3.19. (ERA Rank A).
Erler, D. V. and Eyre, B. D. 2010. Combining Natural Abundance Stable Isotope Signatures and Stable Isotope Tracer Experiments to Quantify Nitrogen Dynamics in a Constructed Wetland. Journal of Environmental Quality 39, 2191-2199.
Erler D.V., B.D. Eyre, L. Davison. 2008. The contribution of anammox and denitrification to sediment N2 production in a surface flow constructed wetland. Environmental Science & Technology 42: 9144-9150.
Erler D.V., B.D. Eyre, L. Davison. 2010. Temporal and spatial variability in the processing of nitrogen in a constructed wetland: a whole system stable isotope addition experiment. Limnology and Oceanography 55: 1172-1187. www.aslo.org/lo/toc/vol_55/issue_3/1172.pdf
Updated: 18 October 2011