University of Vermont ScholarWorks @ UVM Graduate College Dissertations and Theses Dissertations and Theses 2018 Water Quality Performance And Greenhouse Gas Flux Dynamics From Compost-Amended Bioretention Systems & Potential Trade-Offs Between Phytoremediation And Water Quality Stemming From Compost Amendments Paliza Shrestha University of Vermont Follow this and additional works at: https://scholarworks.uvm.edu/graddis Part of the Environmental Sciences Commons, and the Soil Science Commons Recommended Citation Shrestha, Paliza, "Water Quality Performance And Greenhouse Gas Flux Dynamics From Compost-Amended Bioretention Systems & Potential Trade-Offs Between Phytoremediation And Water Quality Stemming From Compost Amendments" (2018). Graduate College Dissertations and Theses. 851. https://scholarworks.uvm.edu/graddis/851 This Dissertation is brought to you for free and open access by the Dissertations and Theses at ScholarWorks @ UVM. It has been accepted for inclusion in Graduate College Dissertations and Theses by an authorized administrator of ScholarWorks @ UVM. For more information, please contact [email protected]. WATER QUALITY PERFORMANCE AND GREENHOUSE GAS FLUX DYNAMICS FROM COMPOST-AMENDED BIORETENTION SYSTEMS & POTENTIAL TRADE-OFFS BETWEEN PHYTOREMEDIATION AND WATER QUALITY STEMMING FROM COMPOST AMENDMENTS A Dissertation Presented by Paliza Shrestha to The Faculty of the Graduate College of The University of Vermont In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Specializing in Plant and Soil Science May, 2018 Defense Date: December 06, 2017 Dissertation Examination Committee: Stephanie E. Hurley, D.Des, Advisor Beverley C. Wemple, Ph.D., Chairperson Elizabeth Carol Adair, Ph.D. Josef H. Görres, Ph.D. Cynthia J. Forehand, Ph.D., Dean of the Graduate College ABSTRACT Stormwater runoff from existing impervious surfaces needs to be managed to protect downstream waterbodies from hydrologic and water quality impacts associated with development. As urban expansion continues, increasing impervious cover, and climate change yields more frequent extreme precipitation events, this increases the need for improved stormwater management. Although green infrastructure such as bioretention has been implemented in urban areas for stormwater quantity and quality improvements, these systems are seldom monitored to validate their performance. Herein, we evaluate flow attenuation, stormwater quality performance, and nutrient cycling from eight roadside bioretention cells. Bioretention cells received varying treatments: (1) vegetation with high (7 species) and low-diversity (2 species) plant mixes; (2) proprietary SorbtiveMediaTM (SM) containing iron and aluminum oxide granules to enhance phosphorus sorption; and (3) enhanced rainfall and runoff (RR) to certain cells, mimicking anticipated precipitation increases from climate change. Bioretention water quality parameters monitored include total suspended solids (TSS), and dissolved and total nitrogen (N) and phosphorus (P) in the cells’ inflows and outflows across 121 storms. Simultaneous measurements of flow rates and volumes allowed for evaluation of the cells’ hydraulic performances and estimation of pollutant load and event mean concentration (EMC) removal. We also monitored soil CO2 and N2O fluxes and determined C and N stocks in the soil media, microbial and vegetation biomass to determine the overall C and N balances in these systems. Significant average reductions in effluent stormwater volumes and peak flows were reported, with 31% of the storms events completely captured. Influent TSS loads and EMCs were well retained by all cells irrespective of treatments, storm characteristics, or seasonality. Nutrient removal was treatment-dependent, where the SM treatments consistently removed P loads and EMCs, and sometimes N as well. The vegetation and RR treatments mostly exported nutrients to the effluent. We attribute observed nutrient exports to the presence of excess compost in the soil filter media. Rainfall depth and peak inflow rate undermined bioretention performance, likely by increasing pollutant mobilization through the filter media. While the bioretention cells were a source of CO2, they varied between being a sink and source of N2O. However, soil C and N, and plant C and N in biomass was seen to largely offset respiratory CO2-C and biochemical N2O-N losses from bioretention soil. The use of compost in bioretention soil media should be reduced or eliminated. If necessary, compost with low P content and high C: N ratio should be considered to minimize nutrients losses via leaching or gas fluxes. To understand trade-offs stemming from compost amendments, we conducted a laboratory pot study utilizing switchgrass and various organic soil amendments (e.g., different compost types and coir fiber) to heavy metal contaminated soils and studied potential nutrient leaching and pollutant uptake. Addition of organic amendments significantly reduced metal bioavailability, and improved switchgrass growth and metal uptake potential. While no differences in soil or plant metal uptake were observed among the amendments, significant differences in nutrient leaching were observed. CITATIONS Material from this dissertation has been published in the following form: Shrestha, P., Hurley, S., Wemple, B.C.. (2018). Effects of different soil media, vegetation, and hydrologic treatments on nutrient and sediment removal in roadside bioretention systems. Ecological Engineering 112: 116-131. Shrestha, P., Hurley, S., Adair, E.C.. In review. Soil media CO2 and N2O fluxes dynamics from sand-based roadside bioretention systems. Water. ii ACKNOWLEDGMENTS I am sincerely grateful towards my adviser, Stephanie Hurley, for giving me the opportunity to work on this project, for continually supporting me with positive feedback and encouragement, and for always believing in me. I thank you for always supporting me to present my work at conferences year after year and backing me up with funding to attend stormwater courses. These experiences have deepened my knowledge on stormwater research and enriched my experience as a graduate student. I could not have asked for a better adviser and mentor for my PhD study. I thank my committee members (Josef Görres, Beverley Wemple, and Carol Adair) for their continuous guidance, support and feedback. Thank you, Josef, for always showing care and warmth, and making me feel like home. Thank you, Josef, Beverley and Carol, for always being there to answer my queries, and help me make substantial progress in my work. I thank my army of interns who made the enormous water sampling effort possible. They are Anna Levine, Iliansherry Santiago, Sam Wooster, Lindsay Cotnoir, Danya AbdelHameid, Jelissa Reynoso, Hannah Klein, Lauren Jenness, Nichole Montero, Wileyshka M. Rivera, Maxwell Landsman-Gerjoi, Jacob Woodworth, Brad Hansen, Julie Stasiuk, Seren Bagcilar, and Page Cascio. Thank you to Joel Tilley for providing laboratory training, Alan Howard and Josef Görres for statistical counseling, as well as Don Ross, Gabriela Buccini, Vanesa Perillo, Anne-Marie Resnik, Mark Starrett, Scott Merrill, Erica Cummings, Joshua Faulkner, Sidney Bosworth, Jason Kokkinos, Amanda Cording, Lindsey Barbieri, and Stephanie Juice. iii Thank you is extended to various agencies for their funds and/or technical assistance towards this project: The Lake Champlain Sea Grant, Lintilhac Foundation, VT EPSCoR, Contech Engineering Solutions, Watershed Consulting Associates, and EcoSolutions. Lastly, I would like to thank my parents (Gayatri Shrestha and Bhola Shrestha) for being a constant source of stability in my life. Finally, I extend my love and gratitude to my beloved husband, Nelish Pradhan, for his unconditional support, endurance and positivity throughout this process. iv TABLE OF CONTENTS Page CITATIONS .................................................................................................................... ii ACKNOWLEDGMENTS .............................................................................................. iii LIST OF TABLES ........................................................................................................... x LIST OF FIGURES ....................................................................................................... xii DISSERTATION OVERVIEW....................................................................................... 1 CHAPTER 1: COMPREHENSIVE LITERATURE REVIEW ...................................... 6 1.1 Urbanization impact on watershed processes ..........................................................6 1.2 Climate change impacts on urban hydrology ..........................................................7 1.3 Importance of green stormwater management ........................................................8 1.4 Bioretention for urban stormwater management ...................................................10 1.5 Bioretention features ..............................................................................................11 1.6 Lake Champlain Research Context .......................................................................13 1.6.1 Climate change prediction for Northeast U.S. ................................................. 15 1.7 Stormwater pollutants in urbanized watersheds and their impacts ........................15 1.7.1 Total suspended solids ..................................................................................... 16 1.7.2 P sources, sinks, and cycling