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51.
Seawater samples were collected in Sagami Bay, western Northwest Pacific Ocean, and their (239+240)Pu activities and (240)Pu/(239)Pu atom ratios were determined by alpha-spectrometry and sector field high-resolution ICP-MS. A few samples also were analyzed for (137)Cs activities. The (239+240)Pu inventory of 41.1 Bq m(-2) was equivalent to the expected cumulative deposition density of atmospheric global fallout at the same latitude and this inventory was considerably lower than inventories in the underlying sediment columns. This result indicated that a significant amount of (239+240)Pu has been removed into the underlying sediments through enhanced scavenging from the water column by the high fluxes of particles in this region. The atom ratio of (240)Pu/(239)Pu showed no notable variation from the surface to the bottom; the average value was 0.234+/-0.004. This atom ratio was significantly higher than the mean global fallout ratio of 0.18, proving the existence of close-in fallout plutonium originating from the Pacific Proving Grounds (PPG). The relative contributions of the global stratospheric fallout and the PPG close-in fallout were evaluated by using the two end-member mixing model. The contribution of the PPG close-in fallout was estimated to be 15.2 Bq m(-2), which corresponded to 37% of the (239+240)Pu inventory in the water column. Thus (239)Pu and (240)Pu from the two sources of global fallout and close-in fallout have been homogenized in the water masses in the western Northwest Pacific margin during the past three decades. 相似文献
52.
Effects of different mobilities of leaf and woody litters on litter carbon dynamics in arid ecosystems in Western Australia 总被引:1,自引:0,他引:1
Shungo Kumada Takuya Kawanishi Yoshishige Hayashi Hiroyuki Hamano Satoko Kawarasaki Shin-ichi Aikawa Nobuhide Takahashi Yasuyuki Egashira Hiroyuki Tanouchi Toshinori Kojima Adrianne Kinnear Koichi Yamada 《Ecological modelling》2009,220(20):2792-2801
Afforestation of arid land is a promising countermeasure against global warming. We had previously found, through modeling and mass balance analyses of an arid land afforestation experimental project in Western Australia, that a significant amount of litter could have been physically removed from the floors of natural forests. In order to analyze litter carbon dynamics in depth, we investigated the actual mobility of litter in several natural forests in Sturt Meadows in an arid region of Western Australia, and estimated the difference between the removal rate of leaf and woody (twigs and branches) litter on the forest floor. Then we redeveloped a litter carbon dynamics model by incorporating physical removal of litter to show the different mobilities of leaf and woody litters. We also analyzed carbon balances and the effect of differential litter mobility on litter carbon dynamics. Except for twigs in one plot in a high density forest, 29–100% of leaf litter and 10–100% of woody litter was removed annually, demonstrating the physical removal of litter in these natural forests. The main cause of litter removal was wind, not flooding. Decreases in leaf and woody litters could be approximated as first order decay functions in most plots; first order decay or disappearance rate constants were then determined. Estimated disappearance rate constants of leaf and woody litter ranged from 0.19 to 11 and 0.11–12 year−1, respectively; most of the constants ranged from 0.19 to 2.0 and 0.11–0.74 year−1, respectively. Based on the disappearance rate constant, the mobility of woody litter was estimated to be roughly 20% that of leaf litter, confirming that climatic factors move leaves more easily than twigs. The improved model, which took into account the different mobilities of leaf and woody litters, showed that annual physical removal of litter reached 70–82% of the annual litter fall in Acacia aneura forests, and that roughly 40–60% of the existing litter was removed annually from all sites. Incorporating into the model the difference in mobilities of leaf and woody litters showed that the ratio of annual litter removal to annual litter fall increased about 10% points compared with the assumption of that both litter types had equal mobility. 相似文献
53.
Takeshi Miyazaki Ryu Ohtani Taichi Ohno Tsuyoshi Takasugi Toshihiro Yamada 《Disasters》2019,43(1):181-205
This paper evaluates the mitigation effect of Tokai earthquake measures on housing damage using a counterfactual approach. It focuses on those measures that stimulate ex‐ante investment in disaster prevention in the supposedly affected area, including earthquake‐proof retrofitting and improved housing construction; the effect of the measures on housing losses is estimated monetarily. The study compares factual disaster damage computed using a real distribution of houses with counterfactual damage to a hypothetical housing distribution that would occur if the measures were not implemented. The key findings are: (i) the disaster mitigation effects of Tokai earthquake measures on housing amount to approximately JPY 18 billion (USD 0.18 billion) for Yamanashi Prefecture and JPY 0.26 trillion (USD 2.6 billion) for Shizuoka Prefecture, which would be at the centre of the event; (ii) a before–after comparison biases estimates of the mitigation effect; and (iii) statistically, the measures do not mitigate the housing damage predicted for an earthquake in Tokai. 相似文献
54.
Amelioration effect of humic acid extracted from solubilized excess sludge on saline-alkali soil 总被引:2,自引:0,他引:2
Hideko Motojima Parida Yamada Mitsuteru Irie Masuo Ozaki Hideyuki Shigemori Hiroko Isoda 《Journal of Material Cycles and Waste Management》2012,14(3):169-180
In this study, the main characteristics and soil amendment effects on the saline–alkali soil of humic acid extracted from solubilized excess sludge (SS-HA) were investigated. The excess sludge was solubilized prior to extraction to improve the humic acid recovery rate. The structural features of SS-HA were characterized by an elemental analysis, Fourier transform infrared spectroscopy, and 1H-nuclear magnetic resonance spectroscopy, and compared with those of HA extracted from non-solubilized excess sludge (ES-HA). The results showed that extraction efficiency of humic acid was enhanced by using solubilization, although structural properties of humic acid extracted from solubilized excess sludge were almost the same as those of ES-HA. To study a utilization method of SS-HA, the soil amendment effects on saline–alkali soil by mixture of SS-HA were investigated with a model soil-column experiment. SS-HA reduced the pH of the saline–alkali soil, and the effect was immediately observed or faster than the case in which only peat is added. Moreover, the cation exchangeable capacity of the saline–alkali soil was enhanced by addition of SS-HA. 相似文献
55.
Akio Kamimura Eisuke Konno Shigehiro Yamamoto Takeru Watanabe Kazuo Yamada Fumiaki Tomonaga 《Journal of Material Cycles and Waste Management》2009,11(2):133-137
The synthesis of recycled plastics from recovered monomeric materials obtained from the depolymerization reaction of fiber-reinforced
plastics (FRP) was examined. The depolymerization reaction of FRP in the presence of N,N-dimethylaminopyridine (DMAP) smoothly yielded the corresponding monomers, which mainly consisted of dimethyl phthalates.
The polymerization reaction with this monomer failed to form the corresponding unsaturated polyesters due to contamination
by N-methyl-4-pyridone, a decomposition product of DMAP. An efficient purification of the recovered monomer was achieved by washing
with water, and the purified monomer successfully yielded the corresponding polymers. A hardness test revealed that the polymers
were as hard as the polyester made from virgin materials. The present modification provides a practical method for the preparation
of recycled plastics from depolymerized plastics. 相似文献
56.
Yuichi Yamaura David Lindenmayer Yusuke Yamada Hao Gong Toshiya Matsuura Yasushi Mitsuda Takashi Masaki 《Conservation biology》2020,34(1):194-206
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
57.
Rumana Tasmin Yohei Shimasaki Michito Tsuyama Xuchun Qiu Fatma Khalil Nozomu Okino Naotaka Yamada Shinji Fukuda Ik-Joon Kang Yuji Oshima 《Environmental science and pollution research international》2014,21(2):1064-1070
In the actual environment, temperatures fluctuate drastically through season or global warming and are thought to affects risk of pollutants for aquatic biota; however, there is no report about the effect of water temperature on toxicity of widely used herbicide diuron to fresh water microalgae. The present research investigated inhibitory effect of diuron on growth and photosynthetic activity of a green alga Pseudokirchneriella subcapitata at five different temperatures (10, 15, 20, 25, and 30 °C) for 144 h of exposure. As a result, effective diuron concentrations at which a 50 % decrease in algal growth occurred was increased with increasing water temperature ranging from 9.2 to 20.1 μg L–1 for 72 h and 9.4–28.5 μg L–1 for 144 h. The photochemical efficiency of photosystem II (F v/F m ratio) was significantly reduced at all temperatures by diuron exposure at 32 μg L–1 after 72 h. Inhibition rates was significantly increased with decreased water temperature (P?<?0.01). Intracellular H2O2 levels as an indicator of oxidative stress were also decreased with increasing temperature in both control and diuron treatment groups and were about 2.5 times higher in diuron treatment groups than that of controls (P?<?0.01). Our results suggest water temperatures may affect the toxicokinetics of diuron in freshwater and should therefore be considered in environmental risk assessment. 相似文献
58.
Koji Yachiguchi Noriko Matsumoto Yuki Haga Motoharu Suzuki Chisato Matsumura Masahiro Tsurukawa Toshihiro Okuno Takeshi Nakano Kimi Kawabe Kei-ichiro Kitamura Akira Toriba Kazuichi Hayakawa Vishwajit S. Chowdhury Masato Endo Atsuhiko Chiba Toshio Sekiguchi Masaki Nakano Yoshiaki Tabuchi Takashi Kondo Shigehito Wada Hiroyuki Mishima Atsuhiko Hattori Nobuo Suzuki 《Environmental science and pollution research international》2014,21(10):6365-6372
To analyze the effect of polychlorinated biphenyl (PCB) 118 on fish bone metabolism, we examined osteoclastic and osteoblastic activities, as well as plasma calcium levels, in the scales of PCB (118)-injected goldfish. In addition, effect of PCB (118) on osteoclasts and osteoblasts was investigated in vitro. Immature goldfish, in which the endogenous effects of sex steroids are negligible, were used. PCB (118) was solubilized in dimethyl sulfoxide at a concentration of 10 ppm. At 1 and 2 days after PCB (118) injection (100 ng/g body weight), both osteoclastic and osteoblastic activities, and plasma calcium levels were measured. In an in vitro study, then, both osteoclastic and osteoblastic activities as well as each marker mRNA expression were examined. At 2 days, scale osteoclastic activity in PCB (118)-injected goldfish increased significantly, while osteoblastic activity did not change significantly. Corresponding to osteoclastic activity, plasma calcium levels increased significantly at 2 days after PCB (118) administration. Osteoclastic activation also occurred in the marker enzyme activities and mRNA expressions in vitro. Thus, we conclude that PCB (118) disrupts bone metabolism in goldfish both in vivo and in vitro experiments. 相似文献
59.
Kajiwara N Kamikawa S Amano M Hayano A Yamada TK Miyazaki N Tanabe S 《Environmental pollution (Barking, Essex : 1987)》2008,156(1):106-114
Polybrominated diphenyl ethers (PBDEs) and organochlorine compounds (OCs) were determined in the blubber of 55 melon-headed whales (Peponocephala electra) mass stranded along the Japanese coasts since 1982. DDTs and PCBs were predominant in all the specimens investigated. In whales that died during the latest event in 2006, concentrations of PBDEs (190–510 ng/g lipid wt) were approximately two orders of magnitude lower than DDTs and PCBs, but comparable with HCHs and HCB. Maternal transfer of PBDEs to offspring through the whole reproductive process was estimated to be 85% of the mother's body burden, while that occurring during gestation was much lower (2.6–3.5%). Concentrations of PCBs, DDTs, and HCB were lower in melon-headed whales stranded after the year 2000 than those stranded in 1982, whereas PBDE and CHL levels showed a temporal increase during the past 20 years, suggesting that the peak of their usage and contamination occurred after the year 1982. 相似文献
60.
cis-Chlordane, trans-chlordane, and heptachlor were photodegraded in ethanol, and their degradation fates and degradation products were determined by a computational chemical method. The most degradable material was heptachlor (first-order reaction constant k=0.13 min(-1)). Chlorine balances changed during UV irradiation, and the chlorine atoms in chlordane and heptachlor were eventually mineralized. cis-Chlordane, trans-chlordane and heptachlor each generated two di-dechlorinated products. Reactivities at various positions in these compounds were predicted on the basis of bond dissociation energies calculated by nonempirical molecular orbital calculation (Gaussian 98W). 相似文献