Aqueous selenium removal and distribution in cattail and duckweed in constructed wetland microcosms

Abstract

Abstract Selenium (Se)‐affected stormwater runoff raises concerns about potential downstream impact of Se on aquatic ecosystems. Unplanted (UNP) detention ponds augmented with cattail (Typha angustifolia L.; CAT) and duckweed (Lemna minor L.; DWD) may provide a solution for continuous, rapid abatement of Se‐affected runoff. This research was conducted to evaluate the efficacy of CAT or DWD and determining the distribution of Se within a continually flooded detain and drain system. Microcosms containing 3 kg of soil planted to either one CAT, 25 g fresh DWD, or left unplanted (UNP, control) were flooded with a 3‐L solution at 40 μg Se L−1, as sodium selenate (Na2SeO4), or a zero Se control. Over two 10‐d flood–discharge cycles (FDCs), plants in microcosms were evaluated in growth chambers maintained at 30 °C under a 12‐h photoperiod with 400 μmol m−2 s−1 irradiance. Initial and final water, soil, plant, and granular activated charcoal (GAC) were analyzed for total [Se] with inductively coupled plasma–mass spectroscopy (ICP–MS). Data were analyzed with PROC GLM (SAS EG 7.1) at α = .05. Within 10 d after Se application, CAT and DWD decreased aqueous Se from 40 μg Se L−1 to below the 11.8 μg Se L−1 threshold. Selenium recovery ranged between 75 and 100% of the applied Se. In continually flooded systems, the primary elimination pathway appears to be associated with the soil solid phase. Cattail and DWD are suitable species for constructed wetland phytoremediation of Se‐affected runoff. The microcosm design presented may be useful for future evaluations.