Accumulation of uranium by aquatic plants in field conditions: Prospects for phytoremediation

Abstract

A study was undertaken to determine Uranium concentrations in water and aquatic plants in the uraniferous region of Beiras, Central Portugal. Samples were collected from running water (n=200) at places where aquatic species were observed. Plant samples were collected from 28 species of submerged, free-floating and rooted emergent plants including 2 bryophytes and 1 pteridophyte. Uranium concentrations in surface waters ranged from 0.23 to 1217μgL−1. The aquatic plant species studied, including several previously untested species, exhibited the ability to accumulate U in concentrations many times that of the ambient water. In general submerged plants exhibited higher U content followed by rooted emergent and free floating species. The highest U concentrations were observed in the bryophyte Fontinalis antipyretica (up to 4979mgkg−1) followed by Callitriche stagnalis (1963mgkg−1), Callitriche hamulata (379mgkg−1), Ranunculus peltatus subsp. saniculifolius (243mgkg−1), Callitriche lusitanica (218mgkg−1), and Ranunculus trichophyllus (65.8mgkg−1). In two out of three rooted emergent species U seemed to be preferentially partitioned in rhizome/roots with highest rhizome U content recorded in Typha latifolia (380mgkg−1). Among the free-floating species, the highest U content (42.5mgkg−1) was seen in Lemna minor. The bryophyte F. antipyretica and Callitrichaceae members seem to be promising candidates for the development of phytofiltration methodologies based on U accumulation, abundance and biomass production.