Co-Authors: E. Brantley, T. Knappenberger, and J. Shaw
Bioretention cells are depressed landscape features filled with a permeable media designed to address stormwater toxicity in urban settings. A well designed bioretention soil media must consider aspects of both soil physics and soil chemistry to ensure proper infiltration rates are met while removing dissolved and particulate pollutants. Although bioretention cells are traditionally composed of sand, silt, clay, and organic matter, research on the incorporation of alternative materials has gained popularity. Ecolite is an aluminosilicate and microporous soil amendment with the potential to increase the infiltration rate and cation exchange capacity of soil. The purpose of this study was to determine the ability of Ecolite to improve the pollutant removal and infiltration rate of bioretention media. One mixture of 85% sand, 11% fines, and 4% organic matter (ALMIX) by volume was included and modified by replacing the sand with zeolite at 2% (AUMIX2), 10% (AUMIX10), and 20% (AUMIX20) volume. A control of 100% sand was included. Each mixture was placed in four columns, resulting in a total of 20 columns arranged in a randomized complete block design. Synthetic stormwater with known concentrations of zinc, copper, nitrate, ammonium, and phosphorus was applied to the columns in four simulated storm events and the effluent was collected. Metal and phosphorus concentrations of the effluent were measured by inductively coupled plasma mass spectrometry, and nitrogen concentrations were measured by spectrophotometry. The effluent pollutant concentrations were log-transformed and analyzed by analysis of variance in R statistical software. ALMIX had the highest mean removal of phosphorus across all storm events with 97.27% removal, but the outflow concentrations were not significantly different from any mixtures amended with Ecolite. All mixtures had significantly lower outflow phosphorus concentrations than the control (p< 0.001). AUMIX10 and ALMIX had the highest mean removal of copper with 85.95% removal, but there was no significant difference between any of the mixtures’ mean outflow copper concentrations (p= 0.96). ALMIX had the highest mean removal of zinc with 98.13% removal, but there was no significant difference between any of the mixtures’ mean outflow zinc concentrations (p= 0.94). Infiltration and nitrogen data are being analyzed and will be included on the poster. Conclusions drawn from this project will increase the available knowledge of alternative materials in bioretention media and their potential for targeted pollutant removal.