Seasonal and spatial variations in the partial pressure of carbon dioxide in a eutrophic brackish lake,Lake Hamana,Japan     

Kubo  Atsushi  Yoshida  Keisuke  Suzuki  Kei 《Journal of Oceanography》2022,78(1):15-23

The dissolved inorganic carbon and total alkalinity in the surface brackish waters of Lake Hamana were investigated monthly from October 2017 to September 2019 at 14 stations. The partial pressure of carbon dioxide (pCO₂) in the surface water ranged from 29 to 1476 μatm and was undersaturated for atmospheric CO₂ during the observation periods, although most coastal waters were net source areas because of the large amount of terrestrial organic and inorganic carbon input. Since there was a strong negative correlation between pCO₂ and the dissolved oxygen, seasonal and temporal variations in pCO₂ were mainly derived from phytoplankton activity. The high phytoplankton activity induced by the effluents from sewage treatment plants, which was low in carbon and high in nitrogen. Therefore, in urbanized coastal waters with sewage treatment plants, such as the coastal waters of Japan, there is a possibility of shifting from weaker carbon dioxide source areas to sink areas. However, pCO₂ was oversaturated at the polluted river mouth, especially after high precipitation events due to the large carbon supply.

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Occurrence of water ponding on soil surfaces depending on infiltration rates on Mongolian rangeland          下载免费PDF全文

Katori Miyasaka  Sho Shiozawa  Kazuhiro Nishida  Siilegmaa Batsukh  Shuichiro Yoshida  Undarmaa Jamsran 《水文研究》2017,31(22):3996-4005

The occurrence of water ponding on soil surfaces during and after heavy rainfall produces surface run‐off or surface water accumulation in low‐lying areas, which might reduce the water supply to soils and result in a reduction of the soil water that plants can use, especially in arid climates. On Mongolian rangeland, we observed ponded water on the surface of a specific soil condition subjected to a heavy rainfall of 30 mm/hr. By contrast, ponded water was not observed for the same type of soil where livestock grazing had been removed for 6–8 years via a fence or for nearby soil containing less clay. We measured the infiltration rate (the saturated hydraulic conductivity of the surface soil, K_s) of the three sites by applying ponded water on the soil surface (an intake rate test). The results showed that K_s in the rangeland was lower than the rainfall intensity in the site where water ponded on the soil surface; however, K_s of the soil inside of the fence has recovered to 3 times that of the soil outside of the fence to exceed the rainfall intensity. Heavy rainfall that exceeds the infiltration rate occurs several times a year at the livestock grazing site where we observed ponded water. Slight water repellency of the soil reduces rain infiltration to increase the possibility of surface ponding for the soil.  相似文献   

Relationships between Kuroko volcanogenic massive sulfide (VMS) deposits, felsic volcanism, and island arc development in the northeast Honshu arc, Japan     

Ryoichi Yamada  Takeyoshi Yoshida 《Mineralium Deposita》2011,46(5-6):431-448

The northeast (NE) Honshu arc was formed by three major volcano-tectonic events resulting from Late Cenozoic orogenic movement: continental margin volcanism (before 21?Ma), seafloor basaltic lava flows and subsequent bimodal volcanism accompanied by back-arc rifting (21 to 14?Ma), and felsic volcanism related to island arc uplift (12 to 2?Ma). Eight petrotectonic domains, parallel to the NE Honshu arc, were formed as a result of the eastward migration of volcanic activity with time. Major Kuroko volcanogenic massive sulfide (VMS) deposits are located within the eastern marginal rift zone (Kuroko rift) that formed in the final period of back-arc rifting (16 to 14?Ma). Volcanic activity in the NE Honshu arc is divided into six volcanic stages. The eruption volumes of volcanic rocks have gradually decreased from 4,600?km³ (per 1?my for a 200-km-long section along the arc) of basaltic lava flows in the back-arc spreading stage to 1,000?C2,000?km³ of bimodal hyaloclastites in the back-arc rift stage, and about 200?km³ of felsic pumice eruptions in the island arc stage. The Kuroko VMS deposits were formed at the time of abrupt decrease in the eruption volume and change in the mode of occurrence of the volcanic rocks during the final period of back-arc rifting. In the area of the Kuroko rift, felsic volcanism changed from aphyric or weakly plagioclase phyric (before 14?Ma), to quartz and plagioclase phyric with minor clinopyroxene (12 to 8?Ma), to hornblende phyric (after 8?Ma), and hornblende and biotite phyric (after 4?Ma). The Kuroko VMS deposits are closely related to the aphyric rhyolitic activity before 14?Ma. The rhyolite was generated at a relatively high temperature from a highly differentiated part of felsic magma seated at a relatively great depth and contains higher Nb, Ce, and Y contents than the post-Kuroko felsic volcanism. The Kuroko VMS deposits were formed within a specific tectonic setting, at a specific period, and associated with a particular volcanism of the arc evolution process. Therefore, detailed study of the evolutional process from rift opening to island arc tectonics is very important for the exploration of Kuroko-type VMS deposits.  相似文献   

2011年日本东北近海地震震源上方的位移     

M.Sato  T.Ishikawa  N.Ujihara  S.Yoshida  M.Fujita  M.Mochizuki  A.Asada  万永革 《世界地震译丛》2011,(3)

2011年3月11日,一次大的板间地震(MW9.0)发生在日本东北宫城县附近的板块交界处。根据余震分布推测的震源区为约500km长、200km宽的近海区(Japan Meteo-rological Agency,2011)。  相似文献   

Application of chemical tracers to an estimate of benthic denitrification in the Okhotsk Sea     

Masanori Ito  Yutaka W. Watanabe  Masahito Shigemitsu  Shinichi S. Tanaka  Jun Nishioka 《Journal of Oceanography》2014,70(5):415-424

To estimate benthic denitrification in a marginal sea, we assessed the usefulness of \({\text{N}}_{2}^{*}\) , a new tracer to measure the excess nitrogen gas (N₂) using dissolved N₂ and argon (Ar) with N* in the intermediate layer (26.6–27.4σ _θ ) of the Okhotsk Sea. The examined parameters capable of affecting \({\text{N}}_{2}^{*}\) are denitrification, air injection and rapid cooling. We investigated the relative proportions of these effects on \({\text{N}}_{2}^{*}\) using multiple linear regression analysis. The best model included two examined parameters of denitrification and air injection based on the Akaike information criterion as a measure of the model fit to data. More than 80 % of \({\text{N}}_{2}^{*}\) was derived from the denitrification, followed by air injection. Denitrification over the Okhotsk Sea shelf region was estimated to be 5.6 ± 2.4 μmol kg^?1. The distribution of \({\text{N}}_{2}^{*}\) was correlated with potential temperature (θ) between 26.6 and 27.4σ _θ (r = ?0.55). Therefore, we concluded that \({\text{N}}_{2}^{*}\) and N* can act complementarily as a quasi-conservative tracer of benthic denitrification in the Okhotsk Sea. Our findings suggest that \({\text{N}}_{2}^{*}\) in combination with N* is a useful chemical tracer to estimate benthic denitrification in a marginal sea.  相似文献   

Magmatism in North-Delhi Fold Belt, NW India: Evidence for Pre-Rodinia Tectonics     

S. Biju-Sekhar  M. Yoshida  M. Santosh  M.K. Pandit 《Gondwana Research》2001,4(2):149

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Effect of rock weathering,clay mineralogy,and geological structures in the formation of large landslide,a case study from Dumre Besei landslide,Lesser Himalaya Nepal   总被引：1，自引：1，他引：0  

Amar Deep Regmi  Kohki Yoshida  Megh Raj Dhital  Krishna Devkota 《Landslides》2013,10(1):1-13

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The design of diamond Compton telescope     

Kinya Hibino  Toshisuke Kashiwagi  Shoji Okuno  Kaori Yajima  Yukio Uchihori  Hisashi Kitamura  Takeshi Takashima  Mamoru Yokota  Kenji Yoshida 《Astrophysics and Space Science》2007,309(1-4):541-544

We have developed radiation detectors using the new synthetic diamonds. The diamond detector has an advantage for observations of “low/medium” energy gamma rays as a Compton telescope. The primary advantage of the diamond detector can reduce the photoelectric effect in the low energy range, which is background noise for tracking of the Compton recoil electron. A concept of the Diamond Compton Telescope (DCT) consists of position sensitive layers of diamond-striped detector and calorimeter layer of CdTe detector. The key part of the DCT is diamond-striped detectors with a higher positional resolution and a wider energy range from 10 keV to 10 MeV. However, the diamond-striped detector is under development. We describe the performance of prototype diamond detector and the design of a possible DCT evaluated by Monte Carlo simulations.   相似文献   

Searching for massive clusters in weak lensing surveys     

Takashi Hamana  Masahiro Takada  Naoki Yoshida 《Monthly notices of the Royal Astronomical Society》2004,350(3):893-913

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The Measurement of the Orientation of the Magnetic Field in Molecular Clouds     

Martin Houde  Ruisheng Peng  Hiroshige Yoshida  Roger H. Hildebrand  Thomas G. Phillips  C. Darren Dowell  Pierre Bastien  Jessie L. Dotson  John E. Vaillancourt 《Astrophysics and Space Science》2004,292(1-4):127-134

We discuss how the combination of polarimetry and ion-to-neutral molecular line width ratio measurements permits the determination of the magnitude and orientation of the magnetic field in the weakly ionized parts of molecular clouds. Polarimetry measurements give the field orientation in the plane of the sky and the ion-to-neutral molecular line width ratio determines the angle between the magnetic field and the line of sight. We show the first results obtained with this technique on the M17 and Orion A star-forming region using Hertz 350 μm polarimetry maps and HCO⁺-to-HCN molecular line width ratios to provide the first view of the spatial orientation of the magnetic field these molecular clouds.  相似文献