Masatsugu Kubota

Composition of storage carbohydrate in tubers of yacon (Polymnia sonchifolia)

Abstract Yacon (Polymnia sonchifolia or P. edulis; Compositae or Asteraceae) plants originating from the Andean highlands have large (100-500 g FW) subterranean tubers, and the fresh, boiled or fried tubers are edible. The appearance of the yacon tubers is similar to that of the dahlia or sweet potato tubers, but the fresh yacon tubers are juicy and sweet like fruits such as pears. Recently, yacon cultivation has been introduced to Japan.

Distribution of different fractions of cadmium, zinc, lead, and copper in unpolluted and polluted soils

McLaren and Crawfords method for fractionating soil Cu was modified, and used to fractionate soil Cd, Zn, Pb, and Cu in 38 soil samples from 11 soil profiles from industrially polluted and nearby unpolluted areas. Pollutant metals, especially Cd and Zn, were more soluble than the native soil metals. On average, approximately 45% of Cd was present in the CaCl2 soluble (CA) fraction, whereas corresponding values for the other metals were below 10%. The percentages of each metal in the CA fraction followed the order Cd > Zn > Pb > Cu. The same order was observed for the acetic acid soluble (AAC) fraction. Approximately 30% of total Pb and Cu were present in the pyrophosphate soluble (PYR) fraction, and only 10% of total Cd and Zn. Approximately 20% of total Zn or Pb and 10% of Cd or Cu were present in the free oxide (OX) fraction. Only 20% of Cd and between 40–50% of the other 3 metals were present in the residual (RES) fraction. The results show that Cd is more labile than the other 3 metals.

Isolation and partial characterization of endophytic diazotrophs associated with Japanese sugarcane cultivar

Abstract Endophytic bacteria were isolated from the juice of a 6 month-old sugarcane cv. NiF-8, which was collected from Miyako, Okinawa and planted in a field lysimeter in Tsukuba, Ibaraki, Japan. The most probable number of N2-fixing endophytes was 4.5 × 105 cells per gram of fresh weight sample and 21 isolates have a positive reaction for ARA in an N2-free semi-solid medium with 10% crystallized sugarcane sugar and 0.5% sugarcane juice. Analyses of some of the biochemical properties of the N2-fixing isolates indicated that 13 isolates were putative strains of Acetobacter diazotrophicus, 4 isolates showed similar characteristics to those of Herbaspirillum seropedicae, and 4 isolates consisted of Herbaspirillum rubribalbicans-like strains. This study confirmed the existence of N2-fixing endophytic bacteria in the Japanese sugarcane cv. NiF-8.

Simultaneous determination of antimony and bismuth in soils by continuous hydride generation—atomic absorption spectrometry

A method for the simultaneous determination of Sb and Bi in soils using an automated hydride generation system with an electrically heated quartz cell atomizer, and an atomic absorption spectrophotometer is described. Five g of the air-dried soil was placed in a 100 mL Erlenmyer flask fitted with a Liebig condenser and boiled gently with 20 mL 6 M HCl for 1 hr on a sand bath. The extract was then filtered into a 100 mL volumetric flask. The two elements in the sample solution (<30 mL) placed in a 50 mL volumetric flask are prereduced by potassium iodide and ascorbic acid solutions. Reduction of Sb and Bi ions to stibine and bismuthine is obtained by sodium tetrahydroborate solution. Detection limits (S/N = 2) are 7 ng g−1 dry soil for Sb and 0.7 ng g−1 dry soil for Bi. The effects of 19 diverse ions on the absorbances of Sb and Bi were investigasted, and it was found that the errors by these ions will be within 5% in the ordinary unpolluted or even polluted soils. In order to examine the accuracy of the proposed method, Sb and Bi in the four Canadian reference soils and NBS-4355 from the National Bureau of Standards in the USA were determined. The values obtained in this work are close to the recommended or the not-certified values. The amounts of Sb, Bi and the related elements in the soils near a smelter were also analyzed.

Evaluation of a sequential extraction procedure for the fractionation of thallium in soils and determination of the content by flame atomic absorption spectrometry

Abstract To evaluate the existing forms of thallium in soils, a slightly modified and reliable procedure of sequential extraction was developed based on the method described by Tessier et al. (Anal. Chem., 51, 844–851, 1979) using samples of Andosols to which a certain amount of thallium was added and cultivated with rice seedlings during 4 months under water-logging conditions in a pot experiment. Five different thallium fractions extracted in soils by this procedure were identified and the amount of thallium was determined using the method of Asami et al. (Fresenius J. Anal. Chem., 356, 348–351, 1996). A preliminary study showed that the detection limit of the amount of thallium determined by flame atomic absorption spectrometry (FAAS) was 0.2 mg L−1, The MgCl2 , CH3COONa, and CH3COONH4 extractants exerted significant effects on the extraction of the thallium fractions that were exchangeable and bound to Fe-Mn oxides, but did not affect the extraction of the other thallium fractions, namely the weak acid-soluble fraction, the fraction bound to organic matter and the residual fraction. It was suggested that the chemical behavior of thallium in soils was characterized by ionic and coordination properties, and that soluble thallium added to soil was mainly bound to Fe-Mn oxides. Moreover, the sequential extraction procedure in the present study showed a good recovery ranging from 85 to 101% in relation to the total amount of thallium determined.

Estimation of the nitrogen fixation by sugarcane cultivar NiF-8 using 15N dilution and natural 15N abundance techniques

Abstract The high population of endophytic diazotrophs in the stalk of the Japanese sugarcane cultivar NiF-8 described in our previous report suggests the possible significant contribution of biological nitrogen fixation (BNF) to the crop nitrogen nutrition. To estimate the amount of BNF in this cultivar, the proportion of biologically fixed nitrogen (%Ndfa) to the plant total nitrogen uptake was determined by 15N dilution and natural 15N abundance (δ15N) techniques. Using the δ15N method, the estimated %Ndfa by the sugarcane cv. NiF-8 under field lysimeter conditions ranged from 32 to 38% at 6 months after planting (MAP) and from 27 to 34% at 7 MAP. With the 15N dilution method, the estimated %Ndfa by the sugarcane plants was 26.0% for the roots, 14.1% for the stem, and 20.5% for the leaves. These results indicate that the sugarcane cv. NiF-8 obtained part of its nitrogen requirements from BNF.

Determination of silver in soils by atomic absorption spectrometry

A method for the determination of Ag in soils using atomic absorption spectrometry is described. The method involves the extraction of Ag from soil by boiling with 6 M HC1 followed by separation of the extracted Ag into methylisobutylketone (MIBK) using sodium N, N-diethyldithiocarbamate (DDTC) as a complexing agent. Silver is determined in the MIBK by direct aspiration into a flame atomic absorption spectrophotometer. The detection limit (S/N=2) for this method is 0.0001 mg L−1 for aqueous solution and 0.002 mg kg−1 for soil. The Ag content of even unpolluted soils can be determined by this method.The determination of Ag using this method was shown to be unaffected by the presence of various ions in the soil. The method was able to recover nearly 100% of Ag added to soil and approximately the same amounts of soil Ag were determined using this method as with HF-H2SO4 decomposition. For 3 reference soils of the Canadian Certified Reference Materials Project (CCRMP), the Ag values obtained by this method were the same as the values determined by Ebarvia et al. (1988).The amounts of Ag in the soils sampled in the Ichi River basin and the Ichi River sediments were determined using this method. This area has been polluted by Cd, Cu, Pb, and Zn discharged from the Ikuno Mine and Smelter. The Ag values ranged from 0.27 to 6.89 mg kg−1 which were much higher than the values of the unpolluted soils.

Heavy metal accumulations in a semi-enclosed hypereutrophic system: Lake Teganuma, Japan: Part 2. Heavy metal accumulations in sediments

Heavy metal concentrations and other physical and chemical properties were studied so as to assess the heavy metal accumulation process in the sediments of a hypereutrophic lake, Lake Teganuma, Japan. The accumulations were most evident near the inflow inlets of two main inflow rivers in Kaminuma (the west part of Lake Teganuma) with the significant Zn accumulation. Except for Fe, the vertical distributions of heavy metals showed the highest concentrations in the surface 10 cm and decreased gradually with the sediment depth. The high concentrations in the upper layer was caused by an increase in the non-residual fractions. The large influx of heavy metal to Lake Teganuma seems to be due to the domestic effluents via the two rivers in last decades.

SOURCE OF NITROUS ACID VOLATILIZED FROM UPLAND SOILS

In order to identify the source of nitrous acid volatilized from upland soils, two experiments were carried out: a 15N tracer experiment and an experiment on the effect of a nitrification inhibitor (thiourea) on nitrous acid volatilization. The following results were obtained. 1) The contribution rate of ammonium-N to the total nitrite-N volatilized was 63–64% in the Taki soil and 61–69% in the Matsuzawa soil, and that of nitrate-N was 23–26% in the Taki soil and 15–18% in the Matsuzawa soil. Recovery of 15N was about 92–96% in both soils. 2) In both soils, the amounts of nitrous acid volatilized decreased by the addition of thiourea. The addition of thiourea-N at a concentration of 10% of the added ammonium-N almost completely suppressed the oxidation of ammonium-N to nitrite-N and nitrate-N in both soils. From these results, it is concluded that a large part of the volatilized nitrous acid originated from ammonium-N.

Background levels of soil beryllium in several countries

Beryllium and aluminium contents in uncontaminated soils from six countries are reported. The means and ranges of beryllium in the surface soils were as follows: 1.43(0.20–5.50)μg g−1 in Thailand (n=28), 0.7 (0.31–1.03) μg g−1 in Indonesia (n=12), 0.99(0.82–1.32) μg g−1 in New Zealand (n=3), 0.58(0.08-1.68)μg g−1 in Brazil (n=16), 3.52(2.49–4.97)μg g−1 in the former Yugoslavia (n=10), and 1.56(1.01–2.73) μg g−1 in the former USSR (n=8). The mean and range of beryllium contents of the surface soils in Japan (1.17(0.27–1.95)μg g−1n=27) are situated within the values of the soils from these countries except for the Yugoslav soils derived from limestones. The mean of the mean beryllium contents of the surface soils in all these countries is 1.42 μg g−1 which will be used as a tentative average content of beryllium in uncontaminated surface soils, except for the soils derived from parent materials high in beryllium content. The beryllium contents of the subsoils were higher than those of the surface soils in New Zealand and Yugoslavia as is the case with Japan. The correlation coefficient between the contents of beryllium and aluminium in all the soil samples (n=113) including surface soils and subsoils was 0.505 (p < 0.001).