Time filter

Source Type

Hamamoto H.,Center for Environmental Science in Saitama | Yamano M.,University of Tokyo | Goto S.,Japan National Institute of Advanced Industrial Science and Technology | Kinoshita M.,Japan Agency for Marine - Earth Science and Technology | And 3 more authors.
Geochemistry, Geophysics, Geosystems | Year: 2011

Detailed heat flow surveys were carried out in the central part of the Nankai Trough southeast of the Kii Peninsula (off Kumano) for investigation of the thermal structure of the subducting plate interface. At stations in the Kumano Trough (forearc basin) and its vicinity, long-term monitoring of temperature profiles in surface sediments was conducted because bottom water temperature variations (BTV) significantly disturb subbottom sediment temperatures. Heat flow values were successfully determined at seven stations by removing the influence of BTV from temperature records for 300 to 400 days. The surface heat flow data were combined with estimates from depths of methane hydrate bottom simulating reflectors to construct a heat flow profile across the subduction zone. Heat flow decreases from 90-110 mW/m2 on the floor of the Nankai Trough to 50-60 mW/m2 at around 30 km from the deformation front, while it is rather uniform, 40-60 mW/m2, in the Kumano Trough. The values measured on the Nankai Trough floor are concordant with the value estimated from the age of the subducting Philippine Sea plate, about 20 m.y., taking into account the effect of sedimentation. The obtained heat flow profile was used to constrain thermal models of the subduction zone. The subsurface thermal structure was calculated using a two-dimensional, steady state model, in which the frictional heating along the plate interface and the radioactive heat production are treated as unknown parameters. Comparison of the calculated surface heat flow in the Kumano Trough with the observed data indicates that the effective coefficient of friction is small, about 0.1 or less, and thus the shear stress on the plate interface is very low in this subduction zone. Copyright © 2011 by the American Geophysical Union. Source

Kishida N.,Japan National Institute of Public Health | Saeki G.,Waseda University | Tsuneda S.,Waseda University | Sudo R.,Center for Environmental Science in Saitama
Water Science and Technology | Year: 2012

In this study, the effectiveness of aerobic granular sludge as seed sludge for rapid start-up of nitrifying processes was investigated using a laboratory-scale continuous stirred-tank reactor (CSTR) fed with completely inorganic wastewater which contained a high concentration of ammonia. Even when a large amount of granular biomass was inoculated in the reactor, and the characteristics of influent wastewater were abruptly changed, excess biomass washout was not observed, and biomass concentration was kept high at the start-up period due to high settling ability of the aerobic granular sludge. As a result, an ammonia removal rate immediately increased and reached more than 1.0 kg N/m 3/d within 20 days and up to 1.8 kg N/m 3/d on day 39. Subsequently, high rate nitritation was stably attained during 100 days. However, nitrite accumulation had been observed for 140 days before attaining complete nitrification to nitrate. Fluorescence in situ hybridization analysis revealed the increase in amount of ammonia-oxidizing bacteria which existed in the outer edge of the granular sludge during the start-up period. This microbial ecological change would make it possible to attain high rate ammonia removal. © IWA Publishing 2012. Source

Ishihara T.,University of Tokyo | Sugai T.,University of Tokyo | Hachinohe S.,Center for Environmental Science in Saitama
Geomorphology | Year: 2012

This paper addresses the influence of sea level changes on the stratigraphy and basal topography of latest Pleistocene-Holocene incised valley fill of the Arakawa and Menuma Lowlands in central Japan by using sedimentary drill cores and columnar geologic sections. In the study area, four buried fluvial terrace surfaces (I to IV) formed in response to sea-level fall during the last glacial period. Surface III is covered with As-YP tephra (15-16.5. ka) and extends at least 65. km landward from the present mouth of the Arakawa River. A buried valley named surface V that extends from at least 85. km upstream from the present river mouth to about 120. m below present sea level on the continental slope was incised in response to the sea-level lowstand of the Last Glacial Maximum. The incised valley fill can be divided into three units: unit A (gravelly river channel sediments including valley-bottom gravels), unit B (fluvial sediments), and unit C (marine sediments), which intertongues within unit B and pinches out up to 60. km upstream from the present river mouth. Unit C marks the landward limit of Holocene transgression. The lower part of unit B is a fining-upward succession formed during rising sea level and indicates retrogressive aggradation of floodplain sediments during transgression, whereas the upper part of unit B was formed during a sea-level highstand. The floodplain migrated more than 85. km upstream from the modern shoreline in response to sea-level rise until the middle Holocene and extends over several tens of kilometers beyond the landward limit of the Holocene marine transgression. © 2011. Source

Kameda Y.,Center for Environmental Science in Saitama | Kimura K.,Saitama City Institute of Health Science and Research | Miyazaki M.,Saitama City Institute of Health Science and Research
Environmental Pollution | Year: 2011

Sun-blocking agents including eight UV filters (UVF) and 10 UV light stabilizers (UVLS) were measured in water and sediment collected from 22 rivers, four sewage treatment plant effluents (STPE) and three lakes in Japan. Total sun blocking agents levels ranged from N.D. to 4928 ng/L and from 2.0 to 3422 μg/kg dry wt in surface water and in sediment, respectively. Benzyl salicylate, benzophenone-3, 2-ethyl hexyl-4-methoxycinnamte (EHMC) and octyl salicylate were dominant in surface water receiving wastewater effluents and STPE, although UV-328, benzophenone and EHMC were dominant in other surface water except background sites. Three UVF and nine UVLS were observed from all sediment and their compositions showed similar patterns with UV-328 and UV-234 as the most prevalent compounds. Homosalate, octocrylene, UV-326, UV-327, UV-328 and UV-234 were significantly correlated with Galaxolide® in sediments. Concentrations of UV-327 and UV-328 also had strong correlation between those of UV-326 in sediment. © 2011 Elsevier Ltd. All rights reserved. Source

Ohura T.,Meijo University | Horii Y.,Center for Environmental Science in Saitama | Kojima M.,University of Shizuoka | Kamiya Y.,Meijo University
Atmospheric Environment | Year: 2013

Concentrations of 3- to 5-ring chlorinated polycyclic aromatic hydrocarbons (ClPAHs) and corresponding PAHs were quantified in 3-h integrated air samples, taken serially over 3-day periods in December 2009 (winter) and August 2010 (summer) in the urban area of Shizuoka, Japan. Twenty species of targeted ClPAHs were detected in both gas and particle phases throughout each campaign. Mean concentrations of total ClPAHs in the winter and summer campaigns were 133±53pgm-3 and 32±27pgm-3, respectively. Throughout the campaigns, diurnal variations of total ClPAHs concentrations did not have periodic fluctuation such as decreasing in daytime and increasing in nighttime, observed in PAHs. However, the mean concentrations of particulate ClPAHs trended to be slightly higher in nighttime than in daytime, but not for gaseous ClPAHs. Significant correlations were observed between the concentrations of total ClPAHs and total PAHs in particulate phase, but not in gaseous phase. In addition, for particulate phase, there were significant correlations between the concentrations of individual ClPAHs and corresponding parent PAHs, nitrate, and chlorine in summer, but not in winter. Considering these behaviors of ClPAHs in the air, the emission sources could have features of as follows: (i) specific emission sources emitted both ClPAHs and PAHs in particulate phase could be present in the area; (ii) particulate ClPAHs could be more strongly influenced by local sources and photochemical reactions rather than by transboundary air pollution; (iii) the possible sources could be combustion processes included biomass and fossil fuels. © 2013 Elsevier Ltd. Source

Discover hidden collaborations