Some unavoidable drawbacks of traditional technologies have made phytoremediation a promising alternative for removal of arsenic from contaminated soil and water. In the present study, the potential of an aquatic macrophyte Spirodela polyrhiza L. for phytofiltration of arsenic, and the mechanism of the arsenic uptake were investigated. The S. polyrhiza L. were grown in three test concentrations of arsenate and dimethylarsinic acid (DMAA) (i.e. 1.0, 2.0 and 4.0 µM) with 0 (control), 100 or 500 µM of phosphate. One control treatment was also set for each test concentrations of arsenic.

The iron uptake and growth of radish sprouts were related to the iron mobility produced by the chelating ligands. These results suggest that, in alkaline media, chelating ligands dissolve the hardly soluble iron hydroxide species, thus increasing iron mobility, iron uptake, and plant growth. HIDS, which is biodegradable, was one of the most effective ligands studied; therefore, this compound would be a good alternative to other environmentally persistent chelating ligands.

Microalgae have been regarded as potential and alternative next‐generation renewable energy sources because of high lipid content in their cell. An efficient light source is pre‐requisite for rapid production of microalgae biomass in photobioreactor in order to produce biofuel, and light emitting diodes (LEDs) have recently been identified as effective and low‐cost energy sources for microalgae cultivation. Green microalga Botryococcus braunii has relatively higher lipid content than other microalgae. In the present study, we investigated the effects of various LEDs with different light wavelengths and illumination intensities on the growth of B. braunii (strain NIES‐836) for the first time. High intensity blue LED was found to be the most effective light source for the growth of the microalga. Monochromatic blue and mixed red‐green‐blue LEDs produced the highest biomass (0.22 and 0.39 mg d wt mL−1, respectively) and relative growth rates (9.20 ± 2.16 and 9.47 ± 2.67 μg d wt mL−1 d−1, respectively) of the microalga. The growth efficiency, in terms of biomass production and energy consumption (mg d wt mL−1 w−1), of the microalga was the highest with blue‐green LED (5.07) followed by red‐green‐blue (4.00) and blue (3.91) LEDs. The highest economic efficiency in terms of power cost and biomass production (mg d wt mL−1 $−1) was obtained with blue‐green LED (182.54) followed by red‐green‐blue (144.74), blue (132.00), and blue‐red (125.83) LEDs indicating that these LEDs would be more cost‐effective than other LEDs for large‐scale cultivation of this microalga. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 269–275, 2015

To aid in the restoration of coastal barren ground areas, it is important to clarify the effects of chelated iron on the growth of seaweed. In particular, for the further development of practical methods to promote seaweed growth, Fe-binding organic ligands, such as humic substances (HSs) composed of humus materials, rather than Fe-binding inorganic ligands, such as ethylenediaminetetraacetic acid (EDTA), should be investigated. In this study, the effects of an Fe-fertilizer, made from HSs and steelmaking slag, on the growth of Sargassum horneri at the germling and immature stages were examined. The addition of the Fe-fertilizer eluate containing Fe-organic ligand complexes clearly promoted the growth of Sargassum horneri at the germling and immature stages. It was also clear that the effect of Fe concentration in the Fe-fertilizer eluate on the growth rate was almost the same as that of Fe-EDTA. Moreover, the addition of the Fe-fertilizer eluate had a great effect on the brown color of Sargassum horneri thalli and promoted the increased content of photosynthetic pigments, such as Chl. a. Based on these experimental results, the application of the Fe-fertilizer containing Fe-organic ligand complexes is expected to become an effective method for the restoration of the barren ground phenomenon in Fe-deficient coastal areas.

The effects of high concentrations of nitrogen sources on the germling growth of Sargassum horneri were investigated for the restoration of coastal barren ground using fertilization materials containing high concentrations of nitrogen. Moreover, the safekeeping period of fertilized eggs of S. horneri was studied to elucidate performance stability as an appropriate method using fertilized eggs. The fertilized eggs of S.horneri that had been preserved in a refrigerator for approximately 170 days were able to grow and demonstrate the same growth curve as those that had been preserved for shorter periods. This demonstrates that our culture method can be applied to examine the effects of nitrogen sources on the contain high concentrations of some nitrogen sources should be carefully considered before they are applied to restore barren ground in nutrient deficient coastal areas.