Characterizing the Impact of Freshwater Salinization on Engineered Ecosystems: Implications for Performance, Resilience, and Self-Repair Through Phytoremediation

Stormwater detention basins are commonly used in the Eastern United States to temporarily store and attenuate stormwater runoff, and also serve as habitats for native and exotic plants. However, during winter, these basins receive saline runoff from road salt application, which contributes to Freshwater Salinization Syndrome (FSS). Since limited research has connected direct measurement of soil and stormwater salinities to biodiversity and phytoremediation potential of salt-tolerant plant species, this thesis aimed to fill this gap. We selected a set of detention basins draining mostly pervious areas, parking lots, or roads in Northern Virginia and measured temporal variations in stormwater and soil salinities, depth profiles of soil salinities, plant community composition, and plant tissue ion concentration. The results indicated elevated levels of sodium, chloride, electrical conductivity (EC), and exchangeable sodium percentage (ESP)/sodium adsorption ratio (SAR) in soil and stormwater after road salt application during winter, followed by a decrease during the growing season for basins draining parking lots and roads. A subsequent increase at the end of the season was observed for all site types. While some stormwater samples exceeded toxicity thresholds, most soil samples did not exceed their respective thresholds nor reach saline or sodic conditions, and native and exotic plant species of both salt-sensitive and salt-tolerant classifications were observed at almost all sites, although proportions of each varied by site type. Tissue analysis of select plants revealed ionic concentrations that generally coincided with observed soil and stormwater concentrations at each major site type. These findings have implications for future detention basin planting regimes to mitigate FSS, and the thesis discusses native plants found to provide the most benefit for phytoremediation.