The geochemistry of lead in rivers,estuaries and the continental shelf of the Southeastern United States     

Herbert L Windom  Ralph G Smith  Masaru Maeda 《Marine Chemistry》1985,17(1):43-56

Transport by southeastern rivers has insignificant influence on the lead concentration of southeastern shelf waters. If the rate of mobilization and transport of lead by these rivers is representative of uncontaminated fluvial transport during the Pleistocene, only about 5% of the prehistoric output of lead to the North Atlantic can be accounted for by river input.Lead concentrations in southeastern shelf waters are similar to those of North Atlantic Water from the upper 1000 m, which is probably similar to the intrusion source water for the shelf. Atmospheric inputs to the shelf of the same magnitude as observed for the Western North Atlantic are difficult to reconcile given the residence time of shelf waters and their lead concentration unless the rate of loss of lead to shelf sediments is about the same as the atmospheric flux.  相似文献   

Microboudin structures of piemontite along the Sambagawa metamorphic belt, Japan: implications for lateral variation of differential stress during regional metamorphism     

T. Masuda  T. Shibutani  T. Ochiai  S. Akagi  H. Yamaguchi  Y. Kugimiya  N. Kimura  T. Miyake 《Journal of Metamorphic Geology》2004,22(3):199-205

Evidence is presented of a lateral variation in differential stress during metamorphism along a regional metamorphic belt on the basis of the proportion of microboudinaged piemontite grains (p) in a quartz matrix in metacherts. It is proposed that p is a practical indicator of relative differential stress. Analysis of 123 metacherts from the 800 km long Sambagawa metamorphic belt, Japan, reveals that p‐values range from < 0.01 to 0.7 in this region. Most samples from Wakayama in the mid‐belt area have p‐values of 0.4–0.6, whereas those from western Shikoku have p‐values of < 0.1. This difference cannot be explained by variations in metamorphic temperature, and is instead attributed to a regional, lateral variation in differential stress during metamorphism.  相似文献   

Photo-inhibition of phytoplankton photosynthesis as a function of exposure time     

Masayuki Takahashi  Sooji Shimura  Yukuya Yamaguchi  Yoshihiko Fujita 《Journal of Oceanography》1971,27(2):43-50

The photo-inhibition of phytoplankton photosynthesis at higher intensities was examined with a cultured marine diatom,Phaeodactylum tricornutum, and natural samples. The question was to determine whether photo-inhibition results from excretion of photosynthetic products from cell or from an actual decrease in photosynthetic rate. P. tricornutum cultured at 15 klux showed very little photo-inhibition up to 70 klux, and, in the sample cultured at 1 klux, most marked photo-inhibition was observed in 3 hours experiment. Extracellular release was less than 30% of particulate fixation, and did not show any extreme increase to supplement photosynthesis depression at higher light intensities. When the photosynthesis was measured during 10 minutes, both samples showed no photo-inhibition. The photosynthesis by low light sample lost the linearity of time-course with prolonged exposure at high light intensity. Observed photo-inhibition, therefore, we explained with the actual decrease in photosynthetic rate. Similar photo-inhibition could be seen in marine phytoplankton samples concentrated by filtration.  相似文献   

Transport of copper from the Bering Sea to the northwestern North Pacific     

Masaru Maeda 《Journal of Oceanography》1986,42(5):333-346

Dissolved copper concentrations in surface waters of the Bering Sea ranged from 106 to 882 ngl^–1. Higher concentrations were found in continental shelf waters. In the northwestern North Pacific dissolved copper ranged from 54 to 140 ngl^–1. Particulate copper concentrations varied regionally and seasonally from 6 to 79 ngl^–1. Regionally averaged particulate copper concentrations decreased from 175 to 33g g^–1 against an increase in suspended materials because of the dilution effects of biological fractions. Apparent sporadic increases in copper concentrations were found in the mixing area of the Kuroshio and the Oyashio waters. The feature is attributed to the lateral distribution of different water types rather than to the upwelling of deeper waters by eddies. In the same area west of 160E, waters with high concentrations of dissolved copper (96±9 ngl^–1) were found. Their origin appears to be the continental shelf of the Bering Sea. In spite of intensive biological activity, a considerable fraction of copper added to shelf waters was transported to the area off Japan via the circulation in the Bering Sea and the Oyashio current.  相似文献   

Bacteria on petroleum globules in the Philippine sea in January, 1973     

Humitake Seki  Hideshi Abe  Yukuya Yamaguchi  Shun-ei Ichimura 《Journal of Oceanography》1974,30(3):151-156

About 10⁶ of total bacteria (direct microscopic count) or heterotrophic bacteria (colony count with Medium 2216E) and about 10⁴ of petroleumlytic bacteria (oil-oxidizing bacteria) were enumerated per square centimeter of the surface of petroleum globules suspended in the topmost 10 meters of water from a station (22°00.2N, 125°51.9E) in the western North Pacific central water, where about 10⁷ of total bacteria, about 10³ of heterotrophic bacteria and about 10 of petroleumlytic bacteria were enumerated per liter of seawater.  相似文献   

Changing anthropogenic influence on the Santa Monica Bay watershed     

Dojiri M  Yamaguchi M  Weisberg SB  Lee HJ 《Marine environmental research》2003,56(1-2):1-14

Santa Monica Bay is an open coastal embayment located directly seaward of Los Angeles, California. The Bay provides vital economic value through its water-dependent activities, such as swimming, diving, boating, and fishing. An increase from 100,000 residents in 1900 to 10 million in 2000 has imposed numerous environmental stressors on the Bay, including urbanization of the watershed. Pollutant discharges into the Bay increased throughout the early part of the century, but declined following passage of the Clean Water Act in 1972. Since that time, the predominant source of pollutant inputs has changed from point sources to non-point urban runoff. To assess how present-day and historical pollution interact to affect the environmental quality of Santa Monica Bay, three organizations collaborated on a multi-disciplinary study in 1997, towards which this volume is focused. This paper details the temporal patterns of anthropogenic influence on Santa Monica Bay to provide context for the papers that follow.  相似文献   

Basalt platforms in Inner Mongolia and Hebei Province, northeastern China: New K–Ar ages, geochemistries, and revision of palaeomagnetic results     

Zhong Zheng  Hidefumi Tanaka  Yoshiyuki Tatsumi  Masaru Kono 《Geophysical Journal International》2002,151(2):654-662

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Report of the International Symposium of IGCP-440 and LEGENDS Proposal in Sri Lanka, March-April 2003     

Masaru Yoshida  Yasuhito Osanai  Masaaki Owada  Nobuhiko Nakano  Wilbert K.W. Kehelpannala 《Gondwana Research》2003,6(4):939-941

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Corrections to Vesicle layering in solidified intrusive magma bodies: a newly recognized type of igneous structure     

Atsushi Toramaru  Akira Ishiwatari  Maki Matsuzawa  Masaru Nakamura  Shoji Arai 《Bulletin of Volcanology》1997,58(8):655-656

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Paleogeographic maps of the Japanese Islands: Plate tectonic synthesis from 750 Ma to the present   总被引：73，自引：1，他引：73  

Shigenori  Maruyama  Yukio  Isozaki  Gaku  Kimura Masaru  Terabayashi 《Island Arc》1997,6(1):121-142

Abstract A series of paleogeographic maps of the Japanese Islands, from their birth at ca 750–700 Ma to the present, is newly compiled from the viewpoint of plate tectonics. This series consists of 20 maps that cover all of the major events in the geotectonic evolution of Japan. These include the birth of Japan at the rifted continental margin of the Yangtze craton ( ca 750-700 Ma), the tectonic inversion of the continental margin from passive to active ( ca 500 Ma), the Paleozoic accretionary growth incorporating fragments from seamounts and oceanic plateaux ( ca 480-250 Ma), the collision between Sino-Korea and Yangtze (250–210 Ma), the Mesozoic to Cenozoic accretionary growth (210 Ma-present) including the formation of the Cretaceous paired metamorphic belts (90 Ma), and the Miocene back-arc opening of the Japan Sea that separated Japan as an island arc (25-15 Ma).  相似文献