Azimuthal dependence on amplifications for long-period ground motions propagating in the Kanto Basin,Japan

Journal of Seismology - In the Kanto Basin, Japan, it has been reported that the dominant periods of long-period ground motions vary depending on the areas where earthquakes occurred. This suggests...     

Nitrate-nitrogen isotopic patterns in surface waters of the western and central equatorial pacific

To understand the processes transporting nitrate to the surface layer of the western and central equatorial Pacific, we measured the nitrogen isotopic ratio of nitrate (δ ¹⁵NO ₃ ⁻ ), which is a very useful tracer of the source of nitrate, above 200 m depth in this region in December 1999. δ ¹⁵NO ₃ ⁻ is higher (about 13.0‰) in the surface water than in the subsurface water (where it is about 6.5‰) due to isotopic fractionation during nitrate uptake by phytoplankton. The δ ¹⁵NO ₃ ⁻ value has a roughly linear relationship with the natural logarithm of nitrate concentration (ln[NO ₃ ⁻ ]). However, for values above 150 m depth, the intercept of this linear relationship varies with position from east to west. On the other hand, the data at 200 m depth at all observation stations are concentrated around a single point (ln[NO ₃ ⁻ ] = 2.5 and δ ¹⁵NO ₃ ⁻ = 6.5‰) and do not fit the linear relationships for the shallower values. To examine the meaning of the observed distributions of δ ¹⁵NO ₃ ⁻ and nitrate concentration we developed a box model including nitrogen and nitrogen isotopic cycles. By reproducing the observed relationship between δ ¹⁵NO ₃ ⁻ and nitrate concentration using this model we found that most nitrate is transported horizontally from the eastern equatorial Pacific. We also conducted case studies and investigated the effects of differences in pathways of nitrate transport on the distributions of δ ¹⁵NO ₃ ⁻ and nitrate concentration. From these studies we concluded that the observed linear relationships between δ ¹⁵NO ₃ ⁻ and ln[NO ₃ ⁻ ], having a common slope around 6‰ but different intercepts at each station, are evidence of the significant horizontal transport of nitrate to the surface water in this area.     

亚太地区环境综合监测的研究方法--APEIS项目研究综述

为了对亚太地区的环境灾害、环境破坏和环境退化及其影响进行监测和评估,由日本环境省发起的亚太地区环境革新战略项日（APEIS)环境综合监测子项（IEM)自2001年开始,建立了一个以MODIS卫星数据和地面观测资料为基础的综合环境监视网络系统。该网络系统起初是由日本国立环境研究所(NIES)和中国科学院地理科学与资源研究所(IGSNRR)共同合作建成的。之后,新加坡国立大学和澳大利亚联邦科学产业研究组织(CSIRO)地球观测中心也正式宣布加入,该系统覆盖整个亚太地区。美国宇航局(NASA)提供了一套MCDIS的高级数据产品,然而,这些产品没能在亚洲地区利用当地的实测资料进行充分地比较和验证。APEIS项目旨在提供利用该地区精确地面观测数据进行了比较验证的高质量数据集。利用该数据集可以推导出水分亏缺指数、沙尘暴指数、地表面温度、土地覆盖变化,以及净第一性生产量等一系列生态环境指标,从而埘环境破坏、环境退化和生态脆弱区进行长期有效的监测。为了评价水资源、食物生产等生态系所提供的产品与服务的现状和变化特征,本研究还开发了一个可利用M0DIS数据的流域环境综合管理模型。该模型已经被用于对流域规模的水、热、碳循环、泥沙转移以及农业生产等生态要素的模拟和评估,并利用高精度的观测资料对其进行了验证。利用该模式可以对流域生态系统所提供的产品与服务的有效利用,以及流域的可持续发展提供一系列战略性的政策选项。     

Identification of Lower Pleistocene widespread tephras associated with large caldera-forming eruptions in the Tohoku area,north-east Japan

Tephra fingerprinting techniques contributing to volcanology and palaeoenvironmental studies have been developed using a combination of laser-ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). In particular, femtosecond LA-ICP-MS can determine major- and trace element abundances in individual glass shards. On the basis of the major oxide and trace element composition of the glass shards, using those methods, we re-examined the identification of four lower Pleistocene tephras originating from north-east Japan. All trace element abundances exhibited the typical pattern of tephras from the Hokkaido–Tohoku area, and major element concentrations were distinct. As a result, we re-examined the correlation of the widespread Tmg-R4 tephra (2.0 Ma), and newly defined the widespread Kd44-Naka tephra (1.968–1.781 Ma), both originating from the Sengan geothermal region. Furthermore, we re-examined identifications of Sr-Asn-Kd8 (1.219 Ma) and Sr-Kc-U8 (0.922–0.910 Ma) in central Japan, both derived from the Aizu volcanic region. The extensive distributions of the former two tephras suggest the occurrence of two large caldera-forming eruptions (Volcanic Explosivity Index 7) during a short period. Also, the distributions and volumes of the latter two tephras are broader and larger than those previously assumed. The results provide insight into large volcanic eruption history and terrestrial and marine palaeoenvironmental history.     

The role of Fischer-Tropsch catalysis in the origin of methane-rich Titan

Fischer-Tropsch catalysis, which converts CO and H₂ into CH₄ on the surface of iron catalyst, has been proposed to produce the CH₄ on Titan during its formation process in a circum-planetary subnebula. However, Fischer-Tropsch reaction rate under the conditions of subnebula have not been measured quantitatively yet. In this study, we conduct laboratory experiments to determine CH₄ formation rate and also conduct theoretical calculation of clathrate formation to clarify the significance of Fischer-Tropsch catalysis in a subnebula. Our experimental result indicates that the range of conditions where Fischer-Tropsch catalysis proceeds efficiently is narrow (T∼500-600 K) in a subnebula because the catalysts are poisoned at temperatures above 600 K under the condition of subnebula (i.e., H₂/CO = 1000). This suggests that an entire subnebula may not become rich in CH₄ but rather that only limited region of a subnebula may enriched in CH₄ (i.e., CH₄-rich band formation). Our experimental result also suggests that both CO and CO₂ are converted into CH₄ within time significantly shorter than the lifetime of the solar nebula at the optimal temperatures around 550 K. The calculation result of clathration shows that CO₂-rich satellitesimals are formed in the catalytically inactive outer region of subnebula. In the catalytically active inner region, CH₄-rich satellitesimals are formed. The resulting CH₄-rich satellitesimals formed in this region play an important role in the origin of CH₄ on Titan. When our experimental data are applied to a high-pressure model for subnebula evolution, it would predict that there should be CO₂ underneath the Iapetus subsurface and no thick CO₂ ice layer on Titan's icy crust. Such surface and subsurface composition, which may be observed by Cassini-Huygens mission, would provide crucial information on the origin of icy satellites.     

The default methods in the 2019 Refinement drastically reduce estimates of global carbon sinks of harvested wood products

With a lack of United States federal policy to address climate change, cities, the private sector, and universities have shouldered much of the work to reduce carbon dioxide (CO2) and other greenhouse gas emissions. This study aims to determine how landcover characteristics influence the amount of carbon (C) sequestered and respired via biological processes, evaluating the role of land management on the overall C budget of an urban university. Boston University published a comprehensive Climate Action Plan in 2017 with the goal of achieving C neutrality by 2040. In this study, we digitized and discretized each of Boston University’s three urban campuses into landcover types, with C sequestration and respiration rates measured and scaled to provide a University-wide estimate of biogenic C fluxes within the broader context of total University emissions. Each of Boston University’s three highly urban campuses were net sources of biogenic C to the atmosphere. While trees were estimated to sequester 0.6 ± 0.2 kg C m−2 canopy cover year−1, mulch and lawn areas in 2018 emitted C at rates of 1.7 ± 0.4 kg C m−2 year−1 and 1.4 ± 0.4 kg C m−2 year−1, respectively. C uptake by tree canopy cover, which can spatially overlap lawn and mulched landcovers, was not large enough to offset biogenic emissions. The proportion of biogenic emissions to Scope 1 anthropogenic emissions on each campus varied from 0.5% to 2%, and depended primarily on the total anthropogenic emissions on each campus. Our study quantifies the role of urban landcover in local C budgets, offering insights on how landscaping management strategies—such as decreasing mulch application rates and expanding tree canopy extent—can assist universities in minimizing biogenic C emissions and even potentially creating a small biogenic C sink. Although biogenic C fluxes represent a small fraction of overall anthropogenic emissions on urban university campuses, these biogenic fluxes are under active management by the university and should be included in climate action plans.     

An attempt to characterize phase Q: Noble gas, Raman spectroscopy and transmission electron microscopy in residues prepared from the Allende meteorite

We have prepared a HF-HCl residue and its oxidized residue of the Allende meteorite and have measured the elemental concentrations and the isotopic compositions of noble gases. In the HF-HCl reside, noble gases are enriched in colloidal fraction compared to the non-colloidal fraction by a factor of 2-4. The heavy noble gases were evidently lost after the oxidization, indicating that phase Q (carrier of planetary heavy noble gases) was removed by the oxidation. The Raman spectroscopic parameters show that the colloidal fraction of the HF-HCl residue is more amorphous compared to the non-colloidal fraction. As the ion irradiation converts carbon into a more amorphous form, our result indicates that the “plasma model” is more plausible than the “labyrinth model” as the origin of phase Q. TEM (Transmission Electron Microscope) observations also show such a trace of ion irradiation. While the TEM observations did not show any large difference between the HF-HCl residue and its oxidized residue, the Raman spectroscopic parameters changed discretely resulting from the oxidization. This observation indicates that the oxidization not only dissolved and removed oxidized carbon, but also changed the carbon structure itself to a more amorphous (disordered) state. The Raman spectroscopic results indicate the possibility that release of Q-gas during oxidation is not accompanied by mass loss and that the release of Q-gas simply resulted from rearrangement of carbon structure during oxidation.     

Monitoring and simulation of water, heat,and CO2 fluxes in terrestrial ecosystems based on the APEIS-FLUX system

1IntroductionInJune1992,theworldsummitorganizedbytheUnitedNations,withparticipantsincludingnationalleadersfromaroundtheworld,concludedwithAgenda21(UnitedNations,1992),theRioDeclarationonEnvironmentandDevelopment,inRiodeJaneiro.Thedeclarationpromptedcountr…     

Atmospheric Corrections Using MODTRAN for TOA and Surface BRDF Characteristics from High Resolution Spectroradiometric/Angular Measurements from a Helicopter Platform

High-resolution spectral radiance measurements were taken by a spectral radiometer on board a heli copter over the US Oklahoma Southern Great Plain near the Atmospheric Radiation Measurements (ARM) site during August 1998. The radiometer has a spectral range from 350 nm to 2500 nm at 1 nm resolution. The measurements covered several grass and cropland scene types at multiple solar zenith angles. Detailed atmospheric corrections using the Moderate Resolution Transmittance (MODTRAN) radiation model and in-situ sounding and aerosol measurements have been applied to the helicopter measurements in order to re trieve the surface and top of atmosphere (TOA) Bidirectional Reflectance Distribution Function (BRDF) characteristics. The atmospheric corrections are most significant in the visible wavelengths and in the strong water vapor absorption wavelengths in the near infrared region. Adjusting the BRDF to TOA requires a larger correction in the visible channels since Rayleigh scattering contributes significantly to the TOA reflectance. The opposite corrections to the visible and near infrarred wavelengths can alter the radiance dif ference and ratio that many remote sensing techniques are based on, such as the normalized difference vege tation index (NDVI). The data show that surface BRDFs and spectral albedos are highly sensitive to the veg etation type and solar zenith angle while BRDF at TOA depends more on atmospheric conditions and the vi ewing geometry. Comparison with the Clouds and the Earth＇s Radiant Energy System (CERES) derived clear sky Angular Distribution Model (ADM) for crop and grass scene type shows a standard deviation of 0.08 in broadband anisotropic function at 25° solar zenith angle and 0.15 at 50° solar zenith angle, respectively.