Bioretention cells under cold climate conditions

Session: 43. - Climate Change Impacts on Ecohydrology of Urbanized Watersheds Draining into Large Lakes

Elodie Passeport, University of Toronto, [email protected]
Brenden Ding, University of Toronto, [email protected]
Fereidoun Rezanezhad, University of Waterloo, [email protected]
Behrad Gharedaghloo, University of Waterloo, [email protected]
Philippe Van Cappellen, University of Waterloo, [email protected]

Abstract

Bioretention cells are a popular stormwater control strategy, but their efficiency for water infiltration and nutrient removal under cold climate conditions has been poorly studied. In this work, bioretention soil column experiments were conducted to obtain a detailed characterization of the soil’s bioretention performance during six consecutive freeze – thaw cycles (FTCs). At the start of each FTC, the columns were supplied with artificial stormwater containing bromide, nitrate and phosphate. The results provided multiple lines of evidence that FTCs may increase the infiltration capacity of the soil. Upon thawing, infiltration rates and the saturated hydraulic conductivity increased. X-ray tomography imaging identified a key role of macro-pore formation in maintaining high infiltration rates. In addition, both aqueous nitrate and phosphate supplied to the columns were almost completely removed from solution. The high retention times and the presence of the internal water storage zone promoted anaerobic nitrate elimination despite the low temperatures. In addition, dissolved phosphate was efficiently trapped at all depths in the soil columns. These findings imply that, when designed properly, bioretention cells can perform effectively for both water flow and nutrient pollution mitigation in cold climate areas.

1. Keyword
water quality

2. Keyword
biogeochemistry

3. Keyword
hydrologic cycle

4. Additional Keyword
bioretention

5. Additional Keyword
freeze-thaw cycles