Effects of heavy oil in the developing spotted halibut, Verasper variegatus

It is well known that heavy oil (HO) on the sea surface causes serious problems in the aquatic environment. In particular, some species of teleosts which develop on the sea surface are thought to be affected by the HO which flows out from tankers or coastal industry. However, the toxicological effects of HO are not fully understood. We performed exposure experiments using the Pleuronectiformean fish, spotted halibut (Verasper variegatus), which is an important fishery resource in Japan. In course of the development, HO-exposed embryos showed remarkable delay in developmental processes including somite formation. We further observed abnormal development of the head morphology. Notably, treated embryos had relatively small eyes and craniofacial structures. These findings strongly suggest that HO seriously affects the cell proliferation and differentiation of the embryo. In addition, HO-exposed embryos showed abnormal neuronal development. We also performed the exposure in the larval stage. Treatment of post-hatching larvae with HO resulted in significantly greater mortality compared with controls. Through these observations, we finally conclude that HO is strongly toxic to halibut in their early life stages.     

Three-dimensional antidunes coexisting with alternate bars

Antidunes are fluvial bedforms that form in rivers with supercritical flows. The water surface over antidunes is strongly in phase with the bed surface, and the water surface is amplified to produce large surface waves. Many experimental studies have addressed antidunes; however, the shapes of three-dimensional antidunes in a wide channel with alternate bars have not yet been appropriately understood. In this study, we experimentally investigated the streamwise and transverse length scales of antidunes under conditions with a large width–depth ratio. Our experimental results provide evidence for the coevolution of antidunes and free alternate bars, and show for the first time that the development of free bars greatly alters the three-dimensional shape of water surface waves over antidunes. In the absence of free bars in a wide channel, multiple longitudinal wave trains form, and the number of wave trains counted in the transverse direction increases with increases in the width–depth ratio. However, the presence of free bars affects the local flow characteristics, resulting in a decrease of the number of wave trains in the transverse direction. Therefore, we propose a simple model for predicting the reduction in the number of wave trains by combining two previous theories for antidunes and free bars. Results obtained by the model were found to largely agree with experimental observations. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd     

Multiple‐indicator study of groundwater flow and chemistry and the impacts of river and paddy water on groundwater in the alluvial fan of the Tedori River,Japan

To investigate the source, flow paths, and chemistry of rich resources of high‐quality, shallow groundwater in the alluvial fan between the Tedori and Sai rivers in central Japan, we analysed stable isotope ratios of H, O, and Sr and concentrations of major dissolved ions and trace elements in groundwater, river water, and paddy water. The ⁸⁷Sr/⁸⁶Sr ratios of the groundwater are related to near‐surface geology: groundwater in sediment from the Tedori River has high ⁸⁷Sr/⁸⁶Sr ratios (>0.711), whereas that from the Sai River in the north of the fan has low ⁸⁷Sr/⁸⁶Sr ratios (<0.711). δ²H and δ¹⁸O values and ⁸⁷Sr/⁸⁶Sr ratios indicate that groundwater in the central and southern fans is recharged by the Tedori River, whereas recharge in the north is from the Sai River. Mg²⁺, Ca²⁺, Sr²⁺, HCO₃^?, and SO₄^2? concentrations and δ²H and δ¹⁸O values in the groundwater are high in the central fan and, except for the northern area, tend to increase with distance from the Tedori River. There are linear relationships between ⁸⁷Sr/⁸⁶Sr ratio and the reciprocal concentrations of Sr²⁺, Mg²⁺, and Ca²⁺. These geochemical characteristics suggest that as groundwater recharged from the Tedori River flows towards the central fan, it mixes with waters derived from precipitation and paddy water that have become enriched in these components during downward infiltration. These results are consistent with our hydrological analysis and numerical simulation of groundwater flow, thus verifying the validity of the model we used in our simulation of groundwater flow. Copyright © 2016 John Wiley & Sons, Ltd.     

Ocean Bottom Seismographs used in a crustal study of an area covered with flood-basalt off Lofoten,N. Norway

Seismic refraction measurements were made in August 1988 to study the crustal structure off Lofoten, Northern Norway. Twenty-four 3-component Ocean Bottom Seismographs (OBS) were used, of which seven were deployed in the area covered by landward-flowing basalt deposited during the early Eocene break-up between Norway and Greenland. The main purpose of the OBS survey was to investigate whether this method can be used to map structures below the basalt, which is not easy to penetrate with conventional seismic reflection techniques. The records obtained showed that the OBS data contain considerable information about structures below the flood-basalt; preopening sediments up to 4.0 km thick is indicated below the 1.0–2.5 km-thick landward-flowing basalt. The success of the OBS survey indicates that such measurements can become an important tool in investigations on passive volcanic margins and, potentially, in other areas where highly reflective boundaries make the reflection technique difficult to apply.     

A flare model deduced from Hinotori and millimeterwave interferometer observations

The -ray and white-light flare of 13 May, 1981 is used for a study of spatial distributions of energetic electrons and high-temperature plasma.     

乌鲁木齐天文站在月球探测同波束干涉测量中的作用

首先简要介绍同波束干涉测量技术,随后叙述中国科学院国家天文台乌鲁木齐天文站在2008年成功完成了约200 h日本月球卫星SELENE同波束较差甚长基线干涉测量,并阐述乌站在此次VLBI中的作用。给出利用SELENE的观测数据,分析、解算出乌站25 m天线与日本VERA网相关台站基线Rstar、Vstar的S1、S2、S3、X频段的较差相关相位、较差相关相位残差,以及对各频段的较差相关相位、较差相关相位残差比对,最后获得较差相位时延。结果显示,同波束甚长基线干涉测量比传统VLBI观测得到的群时延精度提高了1～2个量级。     

The spatial and temporal distributions of spheroidal carbonaceous particles from sediment core samples from industrial cities in Japan and China

Spheroidal carbonaceous particles (SCPs) are produced by the high-temperature combustion of fossil fuels and emitted in to the atmosphere. The distribution and concentration of SCPs in sediments have been used as a proxy for the distribution of pollutants emitted to the atmosphere. However, the effect on the distribution of SCPs due to industrial activity at nearby industrial cities is yet to be quantified. To clarify the origin of SCPs of ~20 μm in size that are preserved in sediments, we evaluated the abundance, surface morphology, and chemical composition of SCPs in sediment core samples recovered from industrial cities in Japan (Tokyo, Osaka, and Nagasaki) and China (Beijing), with the cities being located at least ~500 km away from each other. Vertical profiles of SCP concentration in sediment cores from the Japanese cities and Beijing are different, reflecting the contrasting industrial histories of the two countries. The SCPs from different cities show contrasting morphological and chemical characteristics, suggesting that ~20 μm SCPs in sediments from the industrial cities could represent the local combustion history in detail, as the influx of local SCPs is dominant at such sites.