Sohzoh Suzuki

Growth and 137Cs uptake of four Brassica species influenced by inoculation with a plant growth-promoting rhizobacterium Bacillus pumilus in three contaminated farmlands in Fukushima prefecture, Japan

The effectiveness of the plant growth-promoting rhizobacterium Bacillus pumilus regarding growth promotion and radiocesium ((137)Cs) uptake was evaluated in four Brassica species grown on different (137)Cs contaminated farmlands at Fukushima prefecture in Japan from June to August 2012. B. pumilus inoculation did not enhance growth in any of the plants, although it resulted in a significant increase of (137)Cs concentration and higher (137)Cs transfer from the soil to plants. The Brassica species exhibited different (137)Cs uptake abilities in the order Komatsuna>turnip>mustard>radish. TF values of (137)Cs ranged from 0.018 to 0.069 for all vegetables. Komatsuna possessed the largest root surface area and root volume, and showed a higher (137)Cs concentration in plant tissue and higher (137)Cs TF values (0.060) than the other vegetables. Higher (137)Cs transfer to plants was prominent in soil with a high amount of organic matter and an Al-vermiculite clay mineral type.

Chemical Speciation of Heavy Metals in the Fractionated Rhizosphere Soils of Sunflower Cultivated in a Humic Andosol

Chemical speciation and bioaccumulation factor of iron (Fe), manganese (Mn), and zinc (Zn) were investigated in the fractionated rhizosphere soils and tissues of sunflower plants grown in a humic Andosol. The experiment was conducted for a period of 35 days in the greenhouse, and at harvest the soil system was differentiated into bulk, rhizosphere, and rhizoplane soils based on the collection of root-attaching soil aggregates. The chemical speciations of heavy metals in the soil samples were determined after extraction sequentially into fractions classified as exchangeable, carbonate bound, metal–organic complex bound, easily reducible metal oxide bound, hydrogen peroxide (H2O2)–extractable organically bound, amorphous mineral colloid bound, and crystalline Fe oxide bound. Iron and Zn were predominantly crystalline Fe oxide bound in the initial bulk soils whereas Mn was mainly organically bound. Heavy metals in the exchangeable form accumulated in the rhizosphere and rhizoplane soils, comprising <4% of the total content, suggesting their relatively low availability in humic Andosol. Concentrations of organically bound Fe and Mn in soils decreased with the proximity to roots, suggesting that organic fraction is the main source for plant uptake. Concentrations of Mn and Zn in the metal–organic complex also decreased, indicating a greater ability of sunflower to access Mn from more soil pools. Sunflower showed bioaccumulation factors for Zn, Fe, and Mn as large as 0.39, 0.05, and 0.04 respectively, defining the plant as a metal excluder species. This result suggests that access to multiple metal pools in soil is not necessarily a major factor that governs metal accumulation in the plant.

Determination of total aluminum concentration in soil solution using capillary electrophoresis

Abstract Determination of aluminum ion (Al3+) as total aluminum (Al) was performed using on-line pre concentration (field-amplified sample stacking) with a long sample injection time of 180 s in capillary electrophoresis (CE). A linear calibration curve of the Al concentration was obtained, ranging from 10 to 2,000 µg L −1, with a wide range and good determination coefficient of 0.999. This study suggests that the minimum detectable Al concentration can be increased 12 times and that this method is sensitive enough for soil solution analysis, compared with the results obtained by Gottlein and Blasek (Soil Sci., 161, 705–715, 1996). Determination method of total Al concentration in the soil solution was proposed using CE in this study. Soil solution sample collected from Andosols and buffer solution (p-methylaminophenol sulfate (metol)) were adjusted to pH 2.3 and 3.0, respectively, by the addition of HNO3 as a pretreatment for the determination of the total Al concentration. A capillary 40 cm in length × 75 µm in inner diameter was used in order to determine the total Al concentration and shorten the electrophoresis time. This method provides certain advantages such as a very small total sample volume requirement (< 100 µL) and rapid analysis in soil solutions.