Ariel Lisogorksy, Elodie Passeport, Philippe Van Cappellen, University of Waterloo, Chris Parsons, Mahyar Shafii, Bowen Zhou, Fereidoun Rezanezhad (2022). A detailed look at Phosphorous accumulation in a 12-year old multi-cell bioretention system using sequential extractions. Proceedings of the GWF Annual Open Science Meeting, May 16-18, 2022.

Bioretention cells are an increasingly popular family of urban stormwater management structures that intercept runoff from impervious surfaces. When incorporated into urban catchments, they have been shown to favorably reduce the ‘flashiness’ and overall volume of flow resulting from storm events by promoting storage, groundwater infiltration and evapotranspiration. Studies looking at their impact on Phosphorus (P) have produced varied and conflicting outcomes. Studies looking at more detailed P geochemistry of bioretention systems are necessary to identify the processes that are most likely to be responsible for the divergences in behavior. The SEDEX sequential extraction technique was used to analyze concentrations of six phosphorous fractions in samples collected from a set of12-year-old bioretention cells in Mississauga, ON. P variation in the system was best explained in terms of changes within the redox sensitive (Fe/Mn associated) and organic matter associated ( organic P, humic bound and extractable p) systems which were further corroborated similar trends in Fe/Mn and organic carbon concentrations in the samples. Comparatively, Ca associated P fractions appear to have remained invariant spatially despite evidence for increased Ca concentrations within the media. These results, in addition to the heavy surface bias in concentrations and estimated accumulation rates observed suggest that the system has potential to continue accumulating P for some time and that surface dredging or biomass removal from the surface may be effective for system maintenance. On the other hand, increased concentrations within redox-sensitive pools suggest that anoxic conditions such as those produced during severe flooding may cause this system and others like it to undergo intense leaching events.

AOSM2022 Managing Urban Eutrophication Risks under Climate Change First Author: Ariel Lisogorksy, University of Waterloo Additional Authors: Elodie Passeport, University of Toronto; Philippe Van Cappellen, University of Waterloo; Chris Parsons, Environment and Climate Change Canada; Mahyar Shafii, University of Waterloo; Bowen Zhou, University of Waterloo; Fereidoun Rezanezhad, University of Waterloo