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排序方式: 共有661条查询结果,搜索用时 15 毫秒
101.
Morita T Ohtsuka Y Fujimoto K Minamisako Y Iida R Nakamura M Kayama T 《Marine pollution bulletin》2010,60(12):2311-2322
The anthropogenic radionuclides, 137Cs, 90Sr, 108mAg, 239+240Pu, were measured in two Chionoecetes species, red queen crab (Chionoecetes japonicus) and snow crab (Chionoecetes opilio) collected around Japan during 1996–2007. There was no increase in the concentrations of these radionuclides and no large variation of the atom ratio of 240Pu/239Pu during this research period. These results indicated that the source of the radionuclides was not the radioactive wastes dumped by the former USSR and Russia and originated from past nuclear weapon tests. The higher atom ratio in the crab species than that from global fallout would be contributed by the Pacific Proving Grounds close-in fallout. The variability of the concentration of radionuclides in the crab species would result from the variability of the composition and quantity in the diet. However, the decrease in the concentration of radionuclides with sampling depth would depend on the concentration in the seawater and diet. 相似文献
102.
103.
In this paper, we present a method to quantify the effectiveness of carbon mitigation options taking into account the `permanence' of the emissions reduction. While the issue of permanence is most commonly associated with a `leaky' carbon sequestration reservoir, we argue that this is an issue that applies to just about all carbon mitigation options. The appropriate formulation of this problem is to ask `what is the value of temporary storage?' Valuing temporary storage can be represented as a familiar economic problem, with explicitly stated assumptions about carbon prices and the discount rate. To illustrate the methodology, we calculate the sequestration effectiveness for injecting CO2 at various depths in the ocean. Analysis is performed for three limiting carbon price assumptions: constant carbon prices (assumes constant marginal damages), carbon prices rise at the discount rate (assumes efficient allocation of a cumulative emissions cap without a backstop technology), and carbon prices first rise at the discount rate but become constant after a given time (assumes introduction of a backstop technology). Our results show that the value of relatively deep ocean carbon sequestration can be nearly equivalent to permanent sequestration if marginal damages (i.e., carbon prices) remain constant or if there is a backstop technology that caps the abatement cost in the not too distant future. On the other hand, if climate damages are such as to require a fixed cumulative emissions limit and there is no backstop, then a storage option with even very slow leakage has limited value relative to a permanent storage option. 相似文献
104.
Coastal lagoons are ubiquitous along coastlines worldwide. Here, we compare the abundance of epifauna, seagrass-associated macroinvertebrates, and small fish across a gradient of seagrass cover in shallow coastal lagoons of the northern Gulf of Mexico. Two of the lagoons had little or no seagrass cover (0–18.8 %), and four had high cover (83.8–97.5 %). All of the lagoons were partially covered with fringing marsh. We hypothesized that, due to habitat redundancy between seagrass beds and fringing marshes, seagrass-associated fish and macroinvertebrates would not be largely reduced despite the large differences in seagrass cover among the lagoons. Our results support this hypothesis. For most sampling dates, we did not find significant differences in fish and macroinvertebrate abundance among the lagoons and, when we did, several highly vegetated lagoons did not have larger abundances than sparsely vegetated lagoons. The extreme shallowness of the lagoons studied (<1 m) may also provide further protection from large predatory fishes in the absence of seagrasses. Our results also suggest that marsh detritus, by providing habitat for epifauna and helping maintain prey availability, may further temper reductions in seagrass-associated fishes and macroinvertebrates following seagrass decline. The results highlight the importance of marsh-bordered, shallow lagoons as habitat for small fish and macroinvertebrates regardless of seagrass cover. This study contributes to the characterization of habitat redundancy in coastal ecosystems and pinpoints the importance of considering all habitats in concert for the proper understanding and management of coastal ecosystems. 相似文献
105.
Shark interactions in pelagic longline fisheries 总被引:1,自引:0,他引:1
Eric Gilman Shelley Clarke Nigel Brothers Joanna Alfaro-Shigueto John Mandelman Jeff Mangel Samantha Petersen Susanna Piovano Nicola Thomson Paul Dalzell Miguel Donoso Meidad Goren Tim Werner 《Marine Policy》2008
Substantial ecological, economic and social problems result from shark interactions in pelagic longline fisheries. Improved understanding of industry attitudes and practices towards shark interactions assists with managing these problems. Information on fisher knowledge and new strategies for shark avoidance may benefit sharks and fishers. A study of 12 pelagic longline fisheries from eight countries shows that incentives to avoid sharks vary along a continuum, based on whether sharks represent an economic disadvantage or advantage. Shark avoidance practices are limited, including avoiding certain areas, moving when shark interaction rates are high, using fish instead of squid for bait and deeper setting. Some conventionally employed fishing gear and methods used to target non-shark species contribute to shark avoidance. Shark repellents hold promise; more research and development is needed. Development of specifically designed equipment to discard sharks could improve shark post release survival prospects, reduce gear loss and improve crew safety. With expanding exploitation of sharks for fins and meat, improved data collection, monitoring and precautionary shark management measures are needed to ensure that shark fishing mortality levels are sustainable. 相似文献
106.
A proposal for a new scenario framework to support research and assessment in different climate research communities 总被引:1,自引:0,他引:1
Detlef P. van Vuuren Keywan Riahi Richard Moss Jae Edmonds Allison Thomson Nebojsa Nakicenovic Tom Kram Frans Berkhout Rob Swart Anthony Janetos Steven K. Rose Nigel Arnell 《Global Environmental Change》2012,22(1):21-35
In this paper, we propose a scenario framework that could provide a scenario “thread” through the different climate research communities (climate change – vulnerability, impact, and adaptation - and mitigation) in order to support assessment of mitigation and adaptation strategies and climate impacts. The scenario framework is organized around a matrix with two main axes: radiative forcing levels and socio-economic conditions. The radiative forcing levels (and the associated climate signal) are described by the new Representative Concentration Pathways. The second axis, socio-economic developments comprises elements that affect the capacity for mitigation and adaptation, as well as the exposure to climate impacts. The proposed scenarios derived from this framework are limited in number, allow for comparison across various mitigation and adaptation levels, address a range of vulnerability characteristics, provide information across climate forcing and vulnerability states and span a full century time scale. Assessments based on the proposed scenario framework would strengthen cooperation between integrated-assessment modelers, climate modelers and vulnerability, impact and adaptation researchers, and most importantly, facilitate the development of more consistent and comparable research within and across these research communities. 相似文献
107.
Wataru Takahashi Hiroshi Kawamura Takuo Omura Ken Furuya 《Journal of Oceanography》2009,65(5):647-656
A multi-spectral classification scheme is proposed to identify water with red tide(s) using satellite ocean color imagery
obtained by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). The study area was the eastern Seto Inland Sea in Japan,
where serious red tides frequently occur. “Background Ocean Colors” (BOCs hereafter), or colors of water around a red tide
or those of the water before/after a red tide, are calculated as the monthly climatological average of normalized water-leaving
radiances (nLw) with 0.01 degree spatial resolution with SeaWiFS imagery. Criteria for detecting red-tide pixels are established
from analyses of characteristics of the nLws (in the 443, 490, 510, and 555 nm bands) anomalies from BOCs and the nLw spectra
together with the red-tide records in Osaka Bay. The proposed scheme can efficiently indicate the presence or absence of red
tides for independent match-ups with 83% accuracy. Additional validations of specific events indicate that the algorithm performed
well in the study area. These results suggest that the scheme is appropriate to detect red tides in the optically complex
coastal water of the eastern Seto Inland Sea. 相似文献
108.
Abstract: Low sulphidation epithermal Au-Ag deposits constitute a major exploration target for many mining companies worldwide. These deposits are commonly characterized by quartz vein systems which formed at temperatures often in the range 150–250°C giving rise to major alteration halos. Accompanying mineralization and associated alteration is the destruction and redistribution of magnetite in the host rocks and the formation of various K-bearing minerals such as adularia, illite and alunite. These alteration halos can often cover an area of at least several square kilometres and as such have the potential to be detected during reconnaissance geological surveys utilizing high resolution airborne aeromagnetic and radiometric sensors.
Analysis of airborne magnetic and radiometric data recently acquired over the Hokusatsu Region of SW Kyushu indicates that major low sulphidation epithermal Au-Ag deposits are characterized by several distinct geophysical features varying with the degree of post-mineralization cover and level of erosion. Several deposits coincide with extensive magnetic "flat" and high radiometric K–counts. In addition, several workers have shown that a very close association exists between Bouguer gravity highs and epithermal Au mineralization in the Hokusatsu Region. The combined use of areomagnetics, radiometrics and gravity data therefore provides an exceptionally effective approach to exploration for low sulphidation epithermal Au–Ag deposits in the Hokusatsu Region of Japan. 相似文献
Analysis of airborne magnetic and radiometric data recently acquired over the Hokusatsu Region of SW Kyushu indicates that major low sulphidation epithermal Au-Ag deposits are characterized by several distinct geophysical features varying with the degree of post-mineralization cover and level of erosion. Several deposits coincide with extensive magnetic "flat" and high radiometric K–counts. In addition, several workers have shown that a very close association exists between Bouguer gravity highs and epithermal Au mineralization in the Hokusatsu Region. The combined use of areomagnetics, radiometrics and gravity data therefore provides an exceptionally effective approach to exploration for low sulphidation epithermal Au–Ag deposits in the Hokusatsu Region of Japan. 相似文献
109.
Katherine Calvin Marshall Wise Leon Clarke Jae Edmonds Page Kyle Patrick Luckow Allison Thomson 《Climatic change》2013,117(3):545-560
Most research on future climate change discusses mitigation and impacts/adaptation separately. However, mitigation will have implications for impacts and adaptation. Similarly, impacts and adaptation will affect mitigation. This paper begins to explore these two veins of research simultaneously using an integrated assessment model. We begin by discussing the types of interactions one might expect by impact sector. Then, we develop a numerical experiment in the agriculture sector to illustrate the importance of considering mitigation, impacts, and adaptation at the same time. In our experiment, we find that climate change can reduce crop yields, resulting in an expansion of cropland to feed a growing population and a reduction in bioenergy production. These two effects, in combination, result in an increase in the cost of mitigation. 相似文献
110.
The use of microstructures for discriminating turbiditic and hemipelagic muds and mudstones 下载免费PDF全文
The microstructures of turbiditic and hemipelagic muds and mudstones were investigated using a scanning electron microscope to determine whether there are microstructural features that can differentiate turbiditic from hemipelagic sedimentary processes. Both types of muddy deposits are, in general, characterized by randomly‐oriented clay particles. However, turbiditic muds and mudstones also characteristically contain aggregates of ‘edge‐to‐face’ contacts between clay particles with long‐axis lengths of up to 30 μm. Based on observations of the clay fabric of the experimentally‐formed muds settled from previously agitated muddy fluids, these types of aggregates, hereafter referred to as ‘aggregates of clay particles’, are interpreted as having been formed by the collision of component flocs in turbulent fluids. Furthermore, some aggregates of clay particles have ‘face‐to‐face’ contacts between clay particles; this is similar to face‐to‐face aggregates characteristically developed in fluid‐mud deposits that are commonly recognized only in turbiditic mudstones, indicating the possibility of a final stage of deposition under highly‐dense conditions, such as temporary fluid muds. In conjunction with earlier proposed lithofacies‐based and ichnofacies‐based criteria, aggregates of clay particles should be useful for the differentiation of turbiditic and hemipelagic muddy deposits, particularly with limited volumes of non‐oriented samples from deep‐water successions. 相似文献