Evaluation of the Impacts of De-Icing Salts on the Performance of Bioretention Media in Retaining Phosphorus From Urban Stormwater
Abstract
Bioretention systems are a low impact development system that can remove pollutants such as phosphorus (P) from urban stormwater. P retention in bioretention systems is complicated in cold climate regions due to factors such as inputs of road de-icing salts. This study evaluates the impact of prolonged and periodic salt inputs on P retention by conducting column experiments using three different bioretention media with and without an amendment added. Non-amended columns showed net P release, whereas amended columns showed net P retention. While some non-amended columns showed prolonged salt exposure increases P release, the largest P release for all columns occurred during the freshening period following the switch from high to low salt influent. High porewater pH (> 9) observed during the freshening period may be causing the high P release. This study provides new insights needed to improve year-round P retention in bioretention systems installed in cold climates.