Selenium volatilization and accumulation by twenty aquatic plant species

Aquatic plants can remove selenium (Se) from agricultural or industrial wastewater through Se accumulation and volatilization, that is, the conversion of selenate or selenite to volatile forms of Se. To identify aquatic plant species that will be good at removing Se from contaminated water, 20 plant species were screened for their ability to accumulate and volatilize Se when supplied with 20 μM selenate or selenite under controlled conditions. There was at least a 50-fold variation in Se accumulation and volatilization capacity among the plant species tested, regardless of the form of Se supplied. The best plant species for Se volatilization from selenate were also the best species for selenite volatilization. Selenium volatilization rates were twofold higher from selenite than from selenate but more selenate-Se was translocated into harvestable plant tissues than selenite-Se. Several aquatic plant species showed Se volatilization and accumulation rates (per unit surface area) that were comparable with Indian mustard [Brassica juncea (L.)], the best-known terrestrial plant species for Se phytoremediation. Therefore, many wetland species identified in this study, for example, parrot's feather (Myriophyllum brasiliense Camb.), iris-leaved rush (Juncus xiphioides), cattail (Typha latifolia L.), saltmarsh bulrush (Scirpus robustus), etc., have a great potential for Se phytoremediation in wetlands.