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1.
Tone River supplies most of the water requirements of the Tokyo Metropolitan Area (TMA). Lowering of Tone flow and yearly fluctuation, however, is causing water shortage along TMA nowadays. This study investigated the future water availability scenarios under climatic changes. A state-of-the-art approach to utilize the output of several GCM has been demonstrated to investigate the future water availability scenarios for TMA from the Tone River. An integrated modeling approach for water balance considering several hydrological risk indices was adopted to quantify the future changes in this case. It is observed that the future summer precipitation along the Tone basin is going to be increased considerably, while an almost constant or decreasing trend is observed for winter season. Natural flow availability for winter or spring seasons thus can be crucial under future scenarios. After reservoir routing, the hydrological risk indices estimated, however, were not found to be changed significantly due to the presence of a robust reservoir system at the upstream.  相似文献   
2.
Environmental Fluid Mechanics - The effects of obstacle-height variability on spatial characteristics of turbulent organized structures were investigated with the use of a large-eddy simulation...  相似文献   
3.
Stand structure develops with stand age. Old-growth forests with well-developed stand structure support many species. However, development rates of stand structure likely vary with climate and topography. We modeled structural development of 4 key stand variables and a composite old-growth index as functions of climatic and topographic covariates. We used a hierarchical Bayesian method for analysis of extensive snap-shot National Forest Inventory (NFI) data in Japan (n = 9244) to account for differences in stand age. Development rates of structural variables and the old-growth index exhibited curvilinear responses to environmental covariates. Flat sites were characterized by high rates of structural development. Approximately 150 years were generally required to attain high values (approximately 0.8) of the old-growth index. However, the predicted age to achieve specific values varied depending on environmental conditions. Spatial predictions highlighted regional variation in potential structural development rates. For example, sometimes there were differences of >100 years among sites, even in the same catchment, in attainment of a medium index value (0.5) after timber harvesting. The NFI data suggested that natural forests, especially old natural forests (>150 years), remain generally on unproductive ridges, steep slopes, or areas with low temperature and deep snow, where many structural variables show slow development rates. We suggest that maintenance and restoration of old natural forests on flat sites should be prioritized for conservation due to the likely rapid development of stand structure, although remaining natural forests on low-productivity sites are still important and should be protected.  相似文献   
4.
China has been the largest importer of secondary materials for recycling from Japan during the past decade. In this study, we analyzed the transfer of major secondary materials (plastic, steel, copper, and aluminum scrap) from Japan to China. We identified specific destinations for secondary materials, and the characteristics of secondary materials transferred to China. The major destination for the transfer of secondary materials to China is Guangdong province and part of the Huadong area (Shanghai, Zhejiang, and Jiangsu). Most scrap metal imported into China is of low quality. The destinations of most high-quality nonferrous scrap, imported as processed goods on consignment or through the transit improvement trade, are the northeast border provinces, especially Xinjiang Uighur province. The coefficients of specialization for Chinese cities were different from those for the provinces. Guangdong shows an average recycling structure for China. The structure gradually changes from south to north.  相似文献   
5.
Applying the threshold concept to rangeland management is an important challenge in semi-arid and arid regions. Threshold recognition and prediction is necessary to enable local pastoralists to prevent the occurrence of an undesirable state that would result from unsustainable grazing pressure, but this requires a better understanding of the pastoralists’ perception of vegetation threshold changes. We estimated plant species cover in survey plots along grazing gradients in steppe and desert-steppe areas of Mongolia. We also conducted interviews with local pastoralists and asked them to evaluate whether the plots were suitable for grazing. Floristic composition changed nonlinearly along the grazing gradient in both the desert-steppe and steppe areas. Pastoralists observed the floristic composition changes along the grazing gradients, but their evaluations of grazing suitability did not always decrease along the grazing gradients, both of which included areas in a post-threshold state. These results indicated that local pastoralists and scientists may have different perceptions of vegetation states, even though both of groups used plant species and coverage as indicators in their evaluations. Therefore, in future studies of rangeland management, researchers and pastoralists should exchange their knowledge and perceptions to successfully apply the threshold concept to rangeland management.  相似文献   
6.
To investigate seasonal variations of nutrient distribution in the mudflat–shallow water system, we conducted field surveys once a month from August 2007 to July 2008 in the inner area of Ariake Bay (IAB), Japan. The NH4 +–N concentration of the water column increased in autumn because of the high NH4 + release from the sediments, ranging from 850 to 3,001 μmol?m?2?day?1. The NO3 ?–N concentration was maximal in January, which was thought to be caused by NO3 ? release from the oxic sediments and by NO3 ? regeneration due to water column nitrification. The PO4 3?–P concentration of the water column was high in summer–autumn due to the high PO4 3? release from the reduced sediments, ranging from 22 to 164 μmol?m?2?day?1. We estimated the total amounts of DIN and PO4 3?–P release (R DIN and $ {R_{{\mathrm{P}{{\mathrm{O}}_4}}}} $ , respectively) from the muddy sediment area of the IAB. In summer–autumn, R DIN and $ {R_{{\mathrm{P}{{\mathrm{O}}_4}}}} $ corresponded to about 47.7 % of DIN input and about 116.6 % of PO4 3?–P input from the river, respectively. Thus, we concluded that the muddy sediments were an important source of nutrients for the water column of the IAB during summer–autumn. In addition, we found that phosphorus necessary for the growth of Porphyra (Porphyra yezoensis, Rhodophyceae) would be insufficient in the water column when phosphorus during the Porphyra aquaculture period is supplied only from the river. Therefore, the phosphorus release from the muddy sediments was thought to play an important role in the sustainable production of Porphyra in Ariake Bay.  相似文献   
7.
In this study, improvements of different types of environmental issues in Japan, (i) reduction of mortality risk due to exposure to suspended particulate matter (SPM), (ii) improvement of the water quality of an urban river, and (iii) protection of goshawks, were evaluated in monetary terms using choice experiments. It was found that the reduction of mortality risk and the improvement of the water quality were highly valued, while residents did not place high value on the protection of goshawks. However, scope sensitivity was not observed in the evaluation of each issue and the presence of moral satisfaction was revealed. Excluding the effect of lexicographic choices could partly solve the problem concerning scope sensitivity. The results suggested that non-scope sensitive values that were unrelated to or inconsistent with the level of environmental improvement could be estimated through choice experiments in this research.  相似文献   
8.
There is increasing concern about landfilling of biodegradable wastes. Therefore, biological treatment processes such as composting and biogasification have been considered as alternative strategies for managing those wastes. In this work, life cycle assessment was employed to compare the environmental impacts of landfilling, composting, and biological treatment of municipal solid waste in S?o Paulo City, Brazil. Energy consumption, recovered resources, and emissions to air and water were quantified and analyzed in terms of their potential contribution to global warming, acidification, and nutrient enrichment impact. The results demonstrated that processes that require high levels of energy consumption, such as wastewater treatment, play an important role in the outcome of environmental impact potentials. It was found that the landfilling of all waste is generally the worst strategy from an environmental point of view. However, significant reductions in the resulting impacts can be accomplished through biogasification and composting of the biodegradable fraction. Regarding composting, the application of a biofilter for gas treatment reduced significantly the gaseous emissions.  相似文献   
9.
In the gasification of biomass, it is necessary to limit the amount of by-product tar and increase the yields of hydrogen (H2) and carbon monoxide (CO) (syngas). Therefore, we conducted gasification and reforming experiments on woody biomass using an electric tubular furnace, to evaluate the gas reforming and tar decomposition performance of a NiO/SBA-15 catalyst. As a result, we found that this catalyst is effective for H2 production. It is believed that the increase in H2 volume due to the catalyst occurs through a steam reforming reaction involving hydrocarbons, including methane (CH4), and the water-gas shift reaction. With respect to the influence of the gasifying agent on the reforming effect of the catalyst, the amount of generated carbon dioxide (CO2) and hydrogen (H2) increases because the shift reaction is promoted by supplying steam. On the other hand, it was inferred that the shift reaction rarely occurred because it approaches equilibrium by supplying O2. Furthermore, it is suggested that light aromatic hydrocarbons are decomposed by the catalyst.

Implications: The mesoporous silica catalyst NiO/SBA-15 was highly effective for H2 production and decomposition of light aromatic compounds in the gasification of woody biomass. In the catalyst reaction, supplying steam promoted H2 production. From thermodynamic analysis and discussion, it was also inferred that supplying O2 might prevent the water gas shift reaction. The results are useful for designing a process needed for rich H2 production and gas refining process for further use of syngas.  相似文献   

10.
The amount of carbon dioxide (CO2) absorption and calcium ion (Ca^2+) concentration besides the pH of aqueous solution were observed during the COz absorption to precipitate calcium carbonate (CaCO3) from calcium hydroxide (Ca(OH)2). A reaction rate-limiting effect of an amount of CO2 absorption without any organic additives in the early stage of the precipitation was observed, which was attributed to an interruption effect of bicarbonate ion (HCO3) on the precipitation of CaCO3. The improvement for the reaction rate was achieved not only by amine additives but also by neutral additives such as ε-caprolactam or amine salt. When the hexamethylene diamine was dissolved in the solution, successive change of crystal forms of CaCO3 aragonite to calcite in aqueous suspensions, confirmed by Ca^2+ concentration change and X-ray diffraction, was concluded that a local environment around the amine group in aqueous solution and an interaction of the diamine with precipitated CaCO3 particles were important factors for these reactions.  相似文献   
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