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Land damaged by boron (B) mining should be restored to its natural state with a zero net impact on biodiversity. In an earlier study (Environ. Sci. Technol.2010,44, 7089-7095), we characterized a Turkish ecotype of the grass, Puccinellia distans, which exhibited extreme tolerance to B. Here we evaluated the use of a US ecotype of P. distans as an initial vegetative cover for the phytorestoration of a B mine in southern California. Hydroponic studies revealed that this P. distans ecotype tolerated B concentrations >100 mg B/L and could be germinated and grown in B-contaminated soils taken from the sites to be restored. P. distans grew well in moderately B-contaminated soil (∼88 mg B/L saturated extract) amended with added organic matter (peat moss); other soil treatments such as gypsum addition or pH correction were not needed. P. distans also grew in severely B-contaminated soil (∼1506 mg B/L) provided that toxic levels of soil B were diluted by the addition of sand and/or organic matter. Our results provide evidence in support of the concept of using the US ecotype of P. distans as an initial vegetative cover for the phytorestoration of B-contaminated soil. [ABSTRACT FROM AUTHOR]

The physiological characteristics of the extremely boron (B)-tolerant plant species, Puccinellia distans, were compared with those of the moderately tolerant Gypsophila arrostil, two species collected from a B-mining area of Eskiehir, Turkey. Boron was supplied to plants hydroponically at B concentrations ranging from 0.5 to 50 mg B/L for G. arrostil, and from 0.5 to 2000 mg B/L for P. distans. The results show that P. distans has a strikingly greater tolerance to B than G. arrostil. While G. arrostil was unable to survive B supply concentrations greater than 50 mg B/L, P. distans grew at B supply concentrations exceeding 1250 mg B/L. Our research supports the conclusion that from 0.5 to 50 mg B/L, P. distans is better able to restrict the accumulation of B in the whole plant, and the transport of B from root to shoot, than G. arrostil. We propose that P. distans uses several strategies to achieve B tolerance including the ability to restrict the accumulation of B relative to its accumulation of biomass, the ability to restrict the transport of B from root to shoot, and, to a lesser extent, the ability to tolerate high concentrations of B in its shoot and root tissues. [ABSTRACT FROM AUTHOR]

Magnetic flocculant was synthesized for the highly efficient recovery of microalgal cells. The highest flocculation was achieved using the magnetic flocculant synthesized with iron oxide and 0.1 mg/mL cationic polyacrylamide (CPAM). This resulted in a recovery efficiency of more than 95% within 10 min using a dosage of 25 mg/L for Botryococcus braunii and 120 mg/L for Chlorella ellipsoidea. For both species, the adsorption isotherm data fit the Freundlich model better than the Langmuir model, indicating that the adsorption process was a heterogeneous multilayer. The maximum adsorption capacity was 114.8 and 21.4 mg dry cells/mg-particles at pH 7 for B. braunii and C. ellipsoidea, respectively. The primary flocculation mechanism was bridging, which was assisted by the electrostatic interactions between the microalgal cells and the magnetic flocculant under acidic conditions. These results provide new opportunities and challenges for understanding and improving the harvesting of microalgae using magnetic separation.