Uranium accumulation in aquatic macrophlites in an uraniferous region: Relevance to natural attenuation

Phytoremediation potential of uranium (U) was investigated by submerged, free-floating and rooted emergent native aquatic macrophytes inhabiting along the streams of Horta da Vilarica, a uraniferous geochemical region of NE Portugal. The work has been undertaken with the following objectives: (i) to relate the U concentrations in water sediment plant system; and (ii) to identify the potentialities of aquatic plants to remediate U-contaminated waters based on accumulation pattern. A total of 25 plant species culminating 233 samples was collected from 15 study points along with surface water and contiguous sediments. Concentrations of U showed wide range of variations both in waters (0.61 -5.56 mu g L-1, mean value 1.98 mu g L-1) and sediments (124-23,910 mu g kg(-1), mean value 3929 mu g kg(-1)) and this is also reflected in plant species examined. The plant species exhibited the ability to accumulate U several orders of magnitude higher than the surrounding water. Maximum U concentrations was recorded in the bryophyte Scorpiurium deflexifolium (49,639 mu g kg(-1)) followed by Fontinalis antipyretica (35,771 mu g kg(-1)), shoots of Rorippa sylvestris (33,837 mu g kg(-1)), roots of Oenanthe crocata (17,807 mu g kg(-1)) as well as in Nasturtium officinale (10,995 mu g kg(-1)). Scorpiurium deflexifolium displayed a high bio-concentration factor (BF) of similar to 2.5 x 10(4) (mean value). The species Fontinalis antipyretica, Nasturtium officinale (roots) and Rorippa sylvestris (shoots) exhibited the mean BFs of 1.7 x 10(4), 5 x 10(3) and 4.8 x 10(3) respectively. Maximum translocation factor (TF) was very much pronounced in the rooted perennial herb Rorippa sylvestris showing extreme ability to transport U for the shoots and seems to be promising candidate to be used as bioindicator species. (C) 2016 Elsevier Ltd. All rights reserved.