Dependence of column ozone on future ODSs and GHGs in the variability of 500-ensemble members

Akiyoshi, Hideharu*; Kadowaki, Masanao; Yamashita, Yosuke*; Nagatomo, Toshiharu*

Scientific Reports (Internet), 13, p.320_1 - 320_12, 2023/01

https://doi.org/10.1038/s41598-023-27635-y

State-of-the-art chemistry climate models (CCMs) have indicated that a future decrease in ozone-depleting substances (ODSs) combined with an increase in greenhouse gases (GHGs) would increase the column ozone amount in most regions except the tropics and Antarctic. However, large Arctic ozone losses have occurred at a frequency of approximately once per decade since the 1990s, despite the ODS concentration peaking in the mid-1990s. To understand this, CCMs were used to conduct 24 experiments with ODS and GHG concentrations set based on predicted values for future years; each experiment consisted of 500-member ensembles. The 50 ensemble members with the lowest column ozone in the mid- and high latitudes of the Northern Hemisphere showed a clear ODS dependence associated with low temperatures and a strong westerly zonal mean zonal wind. Even with high GHG concentrations, several ensemble members showed extremely low spring column ozone in the Arctic when ODS concentration remained above the 1980-1985 level. Hence, ODS concentrations should be reduced to avoid large ozone losses in the presence of a stable Arctic polar vortex. The average of the lowest 50 members indicates that GHG increase towards the end of the twenty-first century will not cause worse Arctic ozone depletion.

Radiolysis of boiling water

Yang, S.*; Katsumura, Yosuke*; Yamashita, Shinichi*; Matsuura, Chihiro*; Hiroishi, Daisuke*; Lertnaisat, P.*; Taguchi, Mitsumasa

Radiation Physics and Chemistry, 123, p.14 - 19, 2016/06

https://doi.org/10.1016/j.radphyschem.2016.02.008

-radiolysis of boiling water has been investigated. The G-value of H evolution was found to be very sensitive to the purity of water. In high-purity water, both H and O gases were formed in the stoichiometric ratio of 2:1; a negligible amount of HO remained in the liquid phase. The G-values of H and O gas evolution depend on the dose rate: lower dose rates produce larger yields. To clarify the importance of the interface between liquid and gas phase for gas evolution, the gas evolution under Ar gas bubbling was measured. A large amount of H was detected, similar to the radiolysis of boiling water. The evolution of gas was enhanced in a 0.5 M NaCl aqueous solution. Deterministic chemical kinetics simulations elucidated the mechanism of radiolysis in boiling water.

Sequential radiation chemical reactions in aqueous bromide solutions; Pulse radiolysis experiment and spur model simulation

Yamashita, Shinichi*; Iwamatsu, Kazuhiro; Maehashi, Yuki*; Taguchi, Mitsumasa; Hata, Kuniki; Muroya, Yusa*; Katsumura, Yosuke*

RSC Advances (Internet), 5(33), p.25877 - 25886, 2015/02

https://doi.org/10.1039/C5RA03101J

Pulse radiolysis experiments were carried out to observe transient absorptions of reaction intermediates produced in NO and Ar-saturated aqueous solutions containing 0.9-900 mM NaBr. The most important species among the reaction intermediates are BrOH and Br , which commonly have absorption peaks around 360 nm. The experimental results were compared with the results of simulation based on a spur diffusion model. Each of several complicated sequential radiation-induced chemical reactions was carefully considered, optimizing its rate constant within a range of reported values. All the experimental results were able to be universally reproduced by the simulation, assuming a reaction not yet reported, 2BrOH Br + 2OH, with a rate constant of 3.8 10 M s, which is significant only within 10 micro-s for rather high bromide concentrations ( 10 mM). Primary values, which are yields after sufficient diffusion from the spur to the perimeter region during 100 ns, of major water decomposition products, as well as of the reaction intermediates, were calculated for NO and Ar-saturated conditions as a function of NaBr concentration.

Deposition kinetics and critical deposition concentrations of humic acids with different molecular weight

Yamashita, Yuji; Tanabe, Yosuke*; Adachi, Yasuhisa*

Nogyo Noson Kogakkai Rombunshu, 81(6), p.33 - 37, 2013/12

https://doi.org/10.11408/jsidre.81.521

We obtained breakthrough curves of humic acids with different molecular weight through the column packed with glass beads with various NaCl concentrations. Each breakthrough curve of each humic acid reached almost a stable plateau at which the relative concentration was less than unity. The relative concentrations at each plateau decreased with an increase in the NaCl concentration. Dimensionless deposition rate constants and collision efficiencies of humic acids were calculated. Collision efficiencies were plotted as a function of NaCl concentration to draw a colloidal stability curve. In both humic acids, the obvious boundary points, which were known as the critical deposition concentration (CDC), were obtained from the colloidal stability curve. The value of CDC of smaller molecular weight fraction was higher than that of larger one. In the slow deposition condition, the slope of the stability curve of larger molecular weight fraction was steeper than that of smaller one.

Mechanism of radiation-induced reactions in aqueous solution of coumarin-3-carboxylic acid; Effects of concentration, gas and additive on fluorescent product yield

Yamashita, Shinichi; Baldacchino, G.*; Maeyama, Takuya*; Taguchi, Mitsumasa; Muroya, Yusa*; Lin, M.*; Kimura, Atsushi; Murakami, Takeshi*; Katsumura, Yosuke

Free Radical Research, 46(7), p.861 - 871, 2012/07

https://doi.org/10.3109/10715762.2012.684879

Radiation-induced reactions in aqueous solutions of a water-soluble coumarin derivative, coumarin-3-carboxyl acid (C3CA), have been investigated by pulse radiolysis with 35-MeV electron beam, final product analysis after Co -irradiations, and deterministic model simulations. It was found that C3CA reacts with the hydroxyl radical (OH) as well as the hydrated electron at nearly diffusion-controlled rate constants: 6.810 and 2.110 Ms, respectively. Reactivity of C3CA toward O was not confirmed. Production of a fluorescent molecule 7-hydroxy-coumarin-3-carboxylic acid (7OH-C3CA) was detected by a fluorescence spectrometer coupled with high performance liquid chromatography. Production yields of 7OH-C3CA were in a range from 0.025 to 0.18 (100 eV), depending on irradiation conditions. A variety of the yield with saturating gas, additive, and C3CA concentration implied that there are at least two pathways from scavenging reaction of C3CA toward OH to 7OH-C3CA: peroxidation reaction followed by elimination of perhydroxyl radical and disproportionation reaction. A reaction mechanism involving the two pathways was proposed and incorporated into the simulations, showing good explanation of experimentally measured 7OH-C3CA yields with a constant conversion factor from OH scavenging to 7OH-C3CA production, 4.7%, unless -BuOH is not added.

Spin-trapping reactions of a novel gauchetype radical trapper G-CYPMPO

Oka, Toshitaka; Yamashita, Shinichi; Midorikawa, Masamichi*; Saiki, Seiichi; Muroya, Yusa*; Kamibayashi, Masato*; Yamashita, Masayuki*; Anzai, Kazunori*; Katsumura, Yosuke*

Analytical Chemistry, 83(24), p.9600 - 9604, 2011/10

https://doi.org/10.1021/ac2023926

Chemical reactions of a novel gauche-type spin trap, G-CYPMPO (-5-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-5-methy-1-pyrroline 1-oxide, torsion angle: O1-P1-C6-N1 of 52.8), with reactive oxygen species were examined by pulse radiolysis technique with 35 MeV electron beam and electron spin resonance spectroscopy after Co -ray irradiation. The spin trapping reaction rate constants of G-CYPMPO toward hydroxyl radical and hydrated electron were estimated to be (4.20.1)10 and (11.80.2)10 Ms, respectively. Half-lives of spin adducts, hydroxyl radical and perhydroxyl radical adducted G-CYPMPO were estimated to be 35 and 90 min, respectively. A comparison of the results with earlier reports using different radical sources suggests that the purity of the solution and/or the radical generation technique may influence the stability of spin adducts.

Pulse radiolysis study on free radical scavenger edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one), 2; A Comparative study on edaravone derivatives

Hata, Kuniki; Lin, M.; Katsumura, Yosuke*; Muroya, Yusa*; Fu, H. Y.*; Yamashita, Shinichi; Nakagawa, Hidehiko*

Journal of Radiation Research, 52(1), p.15 - 23, 2011/01

https://doi.org/10.1269/jrr.10060

Temperature and density effects on the absorption maximum of solvated electrons in sub- and super-critical methanol

Yan, Y.*; Lin, M.; Katsumura, Yosuke*; Muroya, Yusa*; Yamashita, Shinichi; Hata, Kuniki; Meesungnoen, J.*; Jay-Gerin, J.-P.*

Canadian Journal of Chemistry, 88(10), p.1026 - 1033, 2010/10

https://doi.org/10.1139/V10-120

The optical absorption spectra of the solvated electron (e) in sub- and super-critical methanol are measured by both electron pulse radiolysis and laser photolysis techniques, at temperatures in the range 220-270 C. Over the density range studied (0.45-0.59 g/cm), the position of the absorption maximum () of e is found to shift only slightly to the red with decreasing density. In agreement with our previous work in water, at a fixed pressure, decreases monotonically with increasing temperature in passing through the phase transition at (239.5 C). By contrast, at a fixed density, exhibits a minimum as the solvent passes above the critical point into the supercritical state. These behaviors are discussed in terms of microscopic arguments based on the changes that occur in the methanol properties and methanol structure in the sub- and supercritical regimes.

Current understanding on radiation chemistry of high temperature and supercritical water

Lin, M.; Katsumura, Yosuke; Muroya, Yusa*; Yamashita, Shinichi

Proceedings of Symposium on Water Chemistry and Corrosion in Nuclear Power Plants in Asia 2009 (CD-ROM), p.66 - 70, 2009/10

Supercritical water cooled reactor (SCWR) is expected to be one of the most promised next generation reactors (GenIV). Proper water chemistry control, in particular, the injection of H into the coolant to convert O and HO into HO by radiolytic processes, may represent the key to keep the integrity of the reactors. In recent years, studies on the radiolytic yields and rate constants up to supercritical conditions were performed. The experimental results show that the radiolytic yields at temperatures above 300C do not follow linear relationship with temperature and there is a very significant density effects under supercritical conditions, especially around . The rate constants of many reactions do not follow linear Arrhenius relationship and there is also strong density dependence under supercritical conditions.

Water radiolysis with heavy ions of energies up to 28 GeV, 2; Extension of primary yield measurements to very high LET values

Yamashita, Shinichi; Katsumura, Yosuke; Lin, M.; Muroya, Yusa*; Maeyama, Takuya*; Murakami, Takeshi*

Radiation Physics and Chemistry, 77(10-12), p.1224 - 1229, 2008/10

https://doi.org/10.1016/j.radphyschem.2008.05.037

Measurements of primary -values (at 10 s after the initial ionizing event) of e, OH and HO were extended to the very high linear energy transfer (LET) region ( 700 eV per nm) near the Bragg peak. Heavy ions (He, C, Ne, Si, Ar and Fe) of energies up to 28 GeV were provided by the Heavy Ion Medical Accelerator in Chiba (HIMAC) of the National Institute of Radiological Sciences (NIRS) in Chiba, Japan. Energies of the ions were decreased down to about 10 MeV per u for He using an energy absorber made of polymethylmethacrylate (PMMA) plates in order to vary the LET values. Beam was visualized after passing through the energy absorber using agarose gel of aqueous solution containing methyl viologen and sodium formate in order to determine how long ions can penetrate into water. Based on the information of the penetration depth of ions in samples, much attention was paid to dose correction and LET evaluation. The obtained data were plotted as a function of ( /) also instead of LET in order to discuss effects of physical track structures on product yields, resulted in better universality.