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Environmental/life science


1. Study on Carbon Cycle in Forest by Using Isotopic Information


2. Study on long-range atmospheric transport in East Asian region with radon isotopes as tracers


3. All element analysis of one biological cell and their chemical speciation for metallomics


4. Application of PIXON image restoration technique to spectroscopic and medical imaging data


5. Sulfur K-edge NEXAFS study on L-cysteine/transition metal (TM=Ni, Cu) under isotope water environment

 


1. Study on Carbon Cycle in Forest by Using Isotopic Information


Development of method has been conducted to evaluate carbon cycle in forests which play an important role by absorbing carbon dioxide (CO2) from the atmosphere. The method uses isotopic ratios of carbon-13 and carbon-14 in atmospheric CO2, soil-respired CO2, soil gas CO2 and soil organic matter (SOM). The method has been tested in a larch forest which represents boreal forest in the Asian continent. A schematic illustration of the observation is shown in Fig.1.

carbon cycle
Fig.1 Schematic diagram of carbon cycle observation in a larch forest.

Observation results showed that the carbon isotopic ratios in the soil-respired CO2 and the atmospheric CO2 in the canopy layer varied diurnally and seasonally reflecting carbon cycle in the forest. A typical example obtained in this series of observation is shown in Fig.2, in which δ13C has maxima before noon and smaller diurnal variations in the warm seasons than in the winter.

Carbon Isotopic ratios of soil-respired CO2
Fig.2 Carbon Isotopic ratios of soil-respired CO2.

It was also shown by the measurements and numerical simulations that these variations in the isotopic ratios were determined by relative contributions of root respiration and SOM decomposition. This is because each component of CO2 source has its own isotopic ratios as shown in Fig.3. SOM in the top several-centimeter layer in the experimental forest has a pronounced peak of δ14C, which resulted in the larger δ14C values in the mornings of the warm seasons when relative contribution from the top soil layer was large due to temperature profile in soil.

carbon-14 in soil organic matter
Fig.3 Isotopic ratio of carbon-14 in soil organic matter.

Fig.4 shows contributions of sources to the soil respiration evaluated by using the isotopic features in the soil-respired CO2. The root respiration was analyzed to be largest in the early summer while the SOM decomposition in late summer when the soil temperature was highest in the year.

Soil respiration components
Fig.4 Soil respiration components evaluated from isotopic ratio of carbon-14.

[Published papers]
  1. W. Liu, J. Moriizumi, H. Yamazawa and T. Iida, "Depth Profiles of Radiocarbon and Carbon Isotopic Compositions of Organic Matter and CO2 in a Forest Soil," J. Enviro. Radioactivity 90 (2006) 210-223.

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2. Study on long-range atmospheric transport in East Asian region with radon isotopes as tracers


The naturally occurring radon isotopes are good tracers of atmospheric contaminants in some aspects. First, radon isotopes have a similarity with man-made contaminants in source geometry in the sense that both are area sources at the surface level. Second, 222Rn has a half-life of 3.8 days, which is suitable in focusing on inter-regional transport phenomena. Third, due to its chemical inertness and low solubility in water, radon can clearly depicts advection and diffusion processes in the atmosphere without additional uncertainty by physical and chemical transformation. The COE program has supported to deploy and run the East Asian atmospheric radon concentration observation network (Fig.5), to which several institutions in Korea, China and Japan have contributed. The observation points are aligned on a line approximately parallel with the wind direction of the winter monsoon in this region.

Radon Network
Fig.5 East Asian atmospheric radon concentration observation network.

A backward trajectory analysis of the radon concentration observed by this network showed clear seasonal variations in the concentration level which correspond to routes of air masses as shown in Fig.6. In winter the observation points in Japan are located in direct downwind of the Asian continent and experience passage of air masses having the radon concentration more than 3 Bqm-3.

A long-range atmospheric transport model was developed. Its performance was examined by using radon observation data from the network. Although the early version of the model was proved to be capable of calculating large concentration variation due to passage of synoptic systems, it tended to underestimate absolute value of surface concentration especially in winter. By analyzing the calculated results in comparison with observed aerological data, that the model performance for surface concentration depends on accuracy of the model in calculating the boundary layer depth and the model tends to overestimate the depth. The short point was resolved by use of a more sophisticated turbulence model and improvements in the numerical schemes for advection-diffusion calculation and in the lateral boundary conditions (Fig.6). We still have substantial uncertainty in the spatial distribution of radon source strength used in the model calculations, which weaken our confidence in the model performance. Development of radon source model is also a topic in this study although details are not presented here.

back trajectory analysis

Fig.6 Results of back trajectory analysis for Hachijo Is. Each panel depicts frequency distribution of concentration classes for the cases of which backward trajectories were analysed to be from the sector in which the panel is shown.

According to a long-term simulation by the model, radon originating from the Asian continent forms a relatively high concentration layer aloft which substantially contribute to high environmental gamma dose rate episodes to occur (Fig.7). It is also shown by the simulation that a cold sector behind a frontal system tends to have high radon concentration and moves eastward to cover Japan (Fig.8: CG animation).

Comparison of surface air radon concentration between model calculation and observation
Fig.7 Comparison of surface air radon concentration between model calculation and observation.

Horizontal distribution of surface air radon concentration
Fig.8 Horizontal distribution of surface air radon concentration.
(A CG animation is available.).

[Published papers]

  1. W. Zhuo, T. Iida and M. Furukawa, "Modeling Radon Flux Density from the Earth's Surface," J. Nucl. Sci. Technol. 43(4) (2006) 479-482.
  2. K. Yoshioka and T. Iida, "The Diurnal Change in the Vertical Distribution of Atmospheric 222Rn Due to the Growth and Rise of the Stable Stratification Height in the Atmospheric Boundary Layer," Radioactivity in the Environment 7 (2005) 489-496.

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3. All element analysis of one biological cell and their chemical speciation for metallomics


Bio-sciences concerned with metallic elements and their applied sciences have been studied independently in many scientific fields such as biochemistry, bioinorganic chemistry, nutritional science, pharmacy, medicine, toxicology, agriculture, environmental science and so forth. All such scientific fields have a deep interrelationship, with the common factor of "metals", from the viewpoint of biological science. Therefore, it is desirable that biometal science is promoted as the interdisciplinary field to integrate the metal-related scientific fields. Thus, H. Haraguchi is newly proposing the academic nomenclature of ''metallomics'' for biometal science. In the study of metallomics, elucidation of the physiological roles and functions of biomolecules binding with metallic ions in the biological systems should be the most important research target. Then, metallomics may be called, in another word, "metal-assisted function biochemistry".

♦All element analysis of one biological cell
In the study on all element analysis of one biological cell chose salmon egg cells as the research objective. In the quantitative experiment, first salmon egg cells were decomposed by the microwave-assisted acid digestion method, and heated almost to dryness. Then, the residue was dissolved with 1 M HNO3 solution to prepare the analysis solution. The analysis solution was subjected to the determination of major and minor elements by ICP-AES and of trace and ultratrace elements by ICP-MS. The concentrations of the elements determined or detected in salmon egg cells are shown in the periodic table of Figure. As is seen in Figure, 72 elements among 78 elements except for radioactive and rare gas elements have been determined in salmon egg cells. It is conclusively stated here that the analytical results shown in Figure indicate the existence of almost elements in one biological cell.

♦Arsenic speciation and distribution in salmon egg cell cytoplasm and cell membrane
Speciation of arsenic in the extracts from salmon egg cell cytoplasm and cell membrane was carried out by an ion-pair HPLC/ICP-MS hyphenated system. The different distributions of arsenic species in egg cell cytoplasm and egg cell membrane may also be interesting to elucidate the physiological functions of arsenic species in egg cell.

elements in salmon egg cell
Fig.9 Concentrations of the elements determined or detected in salmon egg cell.

HPLC chromatograms
Fig.10 HPLC chromatograms for arsenic species in egg cell cytoplasm and membrane.

[Published papers]

  1. H. Haraguchi, "Metallomics as Integrated Biometal Science," J. Anal. At. Spectrom. 19 (2004) 5-14.
  2. H. Matsuura, T. Kuroiwa, K. Inagaki, A Takatsu, and H. Haraguchi, "Arsenic Speciation and Distribution in the Extracts from Salmon Egg Cell Cytoplasm and Cell Membrane by HPLC/ICP-MS," Biomed. Res. Trace Elem. 15 (2004) 37-41.

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4. Application of PIXON image restoration technique to spectroscopic and medical imaging data


It has been developed in a field of statistic to extract minute signals embedded in the sea of quantum noise. Pixon method, a powerful image processing algorithm, has been applied to electron spectroscopic analysis medical imaging data using radioisotopes.

The PIXON method, based on the Baysian theorem, is particularly superior to other similar methods in distinguishing between signal and noise. We thus applied this method to restore the images of the thyroid gland phantom filled with a Na125I aqueous solution, recorded on imaging plates (IP). A representative example is shown in Fig. 11.

PIXON image
Fig.11 (left) Raw IP data. (right)Restored by PIXON method.

The faint and blurred image was impressively restored in the right hand image.
A present problem is that it is difficult to set the correct point-spread-function for the deconvolution. But in future we are planning to develop the method to tomography, for reconstructing a three-dimensional concentration map from the raw data.

[Published papers]

  1. S. Muto, R. C. Puetter and K. Tatsumi: Spectral restoration and energy resolution improvement of electron energy-loss spectra by Pixon reconstruction: I. Principle and test examples, J.Electron Microsc. 55 (2006) 215-223.
  2. S. Muto, K. Tatsumi, R. C. Puetter, T. Yoshida, Y. Yamamoto and Y. Sasano: Spectral restoration and energy resolution improvement of electron energy-loss spectra by Pixon reconstruction: II. Application to practical ELNES analysis of low SNR, J. Electron Microsc. 55 (2006) 225-230.
  3. K. Tatsumi, S. Muto and T. Yoshida: Detection of hydrogen at localized regions by unoccupied electronic states in iron carbides: Towards high spatial resolution mapping of hydrogen distributions, J. Appl. Phys. 101 (2007) 023523-1-7.

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5. Sulfur K-edge NEXAFS study on L-cysteine/transition metal (TM=Ni, Cu) under isotope water environment


For the application to medical materials, it is important to study a mechanism of reaction at interface between an amino acid, which is a component of protein, and a metal surface. An adsorption reaction between sulfur-including molecule, especially thiol group molecule, and transition metal surface shows some unique behaviors. It has a great importance to clarify the changing for the chemical state about the adsorption behavior, chemical state and adsorption structure about a sulfur-including amino acid molecule, such as L-cysteine [HSCH2CH(NH2)COOH]. The L-cysteine molecules are a free amino acid. Though those molecules are existing in our body, many functions are not cleared. When we pay attention to the isotope water molecules, an ionizing level of the heavy water (D2O) is about 1/7 of the light water (H2O). It is thought that the difference of the ionizing level has some influences upon the adsorption reaction of the L-cysteine under the isotope water environment. It aims to clarify the co-adsorption reaction of the L-cysteine and the isotope water molecule on Ni or Cu surfaces, which are familiar transition metal in our living.

NEXAFS spectra

Fig.12 Sulfur K-edge NEXAFS spectra for multilayer, aqueous solution, /Ni or /Cu under light water environment.

Figure shows the sulfur K-edge NEXAFS spectra for L-cysteine multilayer film, L-cysteine aqueous solution, L-cysteine/Ni or /Cu under light water environment from the top. A peak for L-cysteine aqueous solution can observe at 2471.9 eV, and the peak shifts to lower photon energy side of about 0.9 eV in comparison with that of the multilayer film. The peak is assigned to the transition from sulfur 1s to δ*(S-C) orbital. This result indicates that the S-C bond length is elongated, due to the interaction between L-cysteine and light water molecules. The peaks of δ*(S-C) for L-cystine/Ni or /Cu are located at 2472.2eV and 2472.5 eV, respectively. These peaks show that the S-H bonding decomposes on the metal substrates and the adsorbed molecule becomes a thiolate state. There is a large peak with a wide FWHM at around 2481 eV. Because the peak position is almost same as that of SO32- or SO42-, it seems that the peak is associated with the chemical state of oxidized sulfur. Therefore, it assumes that there are three or four water molecules around the sulfur atom of L-cysteine adsorbed on Ni or Cu surface under the light water environment. The peak around 2481 eV disappears after drying process, not shown here, and the peak around 2470 eV is clearly observed on both sutfaces. Those results indicate that the L-cysteine dissociates into the atomic sulfur. It is assumed that the light water molecules prevent the L-cysteine from the decomposition under the water environment, and it stabilize the molecularly adsorption behavior.

[Published papaers]

  1. S. Yagi, Y. Matsumura, T. Nomoto, K. Soda, E. Hashimoto, H. Namatame and M. Taniguchi: Liquid-solid interface of L-cysteine/TM (TM = Ni and Cu) in aqueous solution by means of sulfur K-edge NEXAFS, Surf. Sci. in press (2007).
  2. Shinya Yagi, Toyokazu Nomoto, Takaki Ashida, Kazuya Miura, Kazuo Soda, Kazue Yamagishi, Noriyasu Hosoya, Ghalif Kutluk, Hirofumi Namatame and Masaki Taniguchi: XAFS Measurement System for Nano, Bio and Catalytic Materials in Soft X-ray Energy Region, AIP Conference Proceedings 879 (2007) 1638-1641.

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