PHYTOREMEDIATION OF SELENIUM-IMPACTED WATER BY AQUATIC MACROPHYTES

Abstract. Stormwater runoff raises concern over potential downstream impacts of selenium (Se) on aquatic ecosystems. Constructed wetland phytoremediation is a sustainable, inexpensive, eco-friendly technology with potential to remove Se from stormwater. The objectives of this study were to: 1) evaluate the bioavailability of Se chemical form and concentration on plant uptake and 2) determine the potential of aquatic macrophytes to improve water quality in a constructed wetland. The experiment was arranged as a 2 X 2 factorial nested within a split-split plot design replicated three times. Cattail (CT; Typha angustifolia L.), duckweed (DWD; Lemna minor L.), fanwort (CAB; Cabomba caroliniana A. Gray), soft rush (SR; Juncus effuses L.), muskgrass (MG; Chara spp.), and unplanted controls (UNP) were acclimatized 14 d in 115-L microcosms containing 0.035 m of Catalpa silty clay loam with 26 L of water supplemented with 0.1 N Hoagland’s solution. Selenium treatments were applied as a 4-L solution of either sodium selenite (SeO3 ) or sodium selenate (SeO4 ) to a total volume of 30 L at 0, 500, or 1000 μg Se L. Water samples were collected daily for six days. Plant and soil samples were collected prior to Se application and at three-day intervals post Se application. Water, plant, and soil samples were analyzed for total [Se] by inductively coupled plasma-mass spectrometry. Data were analyzed with PROC GLM at α=0.05. After six days, CT and MG-planted microcosms significantly decreased aqueous [Se] by 75 and 74%, respectively, compared to 61% for UNP. The aqueous fraction of microcosms planted to CAB, DWD, and SR were similar to UNP controls. Plant tissue Se content in CT was significantly less than CAB, DWD, or MG, suggesting CT has the potential to volatilize Se. Given its abundance and efficacy, CT is likely a suitable species for Se removal in constructed wetlands supplied with either selenite or selenate-impacted waters. Additional