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排序方式: 共有185条查询结果,搜索用时 485 毫秒
41.
Diego Romero Jacqueline James Rodrigo Mora Carol D. Hays 《Waste management (New York, N.Y.)》2013,33(7):1659-1666
Cathode ray tube (CRT) glass is considered a hazardous material due to its lead toxicity. In addition, current disposal practices are being phased out due to their adverse environmental impacts. In this project, CRT glass was used as a fine aggregate replacement in concrete. Life-cycle material characterization was conducted by evaluating the durability and strength of the CRT-Concrete. Leaching tests were also conducted to investigate whether the material meets drinking water limits for Pb. Test results show that the plastic state of the CRT-Concrete was affected by the angularity of the glass particles. Moreover, the compressive strength of CRT-Concrete met and exceeded that of the control specimen. However, CRT-Concrete was susceptible to expansive alkali-silica reactions when more than 10% CRT replacement was used. Environmental leaching results show that lead concentrations from CRT-Concrete are below the drinking water limits depending on the CRT volume replacement and if biopolymers are used. 相似文献
42.
Foam extrusion of biodegradable polyester [poly(butylene adipate-co-terephthalate) (PBAT)] and its blends with maleated thermoplastic
starch (MTPS) using a chemical blowing agent was performed. The effect of MTPS and percentage of chemical blowing agent on
various foam properties is discussed. In general, an increased amount of PBAT in the foams improves the properties of the
foams. The foam samples were characterized by measurements of density, expansion ratio, specific length, compressive strength,
resiliency, moisture sorption, and imaging using digital light microscopy. Density, expansion ratio, and specific length measurements
show that the best characteristics of lowest density, highest expansion ratio, and highest specific length are exhibited by
the PBAT samples. The compressive strength and foam density exhibit a power-law relationship. Greater amounts of PBAT in the
samples increase the resiliency and decrease the steady state weight gain during moisture sorption. All samples show regions
of unfoamed material when only 3% chemical blowing agent is used, but when 5 and 7% chemical blowing agent is used, the samples
exhibit cells throughout the matrix. 相似文献
43.
Management of ecological reserve lands should rely on the best available science to achieve the goal of biodiversity conservation.
“Adaptive Resource Management” is the current template to ensure that management decisions are reasoned and that decisions
increase understanding of the system being managed. In systems with little human disturbance, certain management decisions
are clear; steps to protect native species usually include the removal of invasive species. In highly modified systems, however,
appropriate management steps to conserve biodiversity are not as readily evident. Managers must, more than ever, rely upon
the development and testing of hypotheses to make rational management decisions. We present a case study of modern reserve
management wherein beavers (Castor canadensis) were suspected of destroying habitat for endangered songbirds (least Bell’s vireo, Vireo bellii pusillus, and southwestern willow flycatcher, Empidonax traillii extimus) and for promoting the invasion of an exotic plant (tamarisk, Tamarix spp.) at an artificial reservoir in southern California. This case study documents the consequences of failing to follow
the process of Adaptive Resource Management. Managers made decisions that were unsupported by the scientific literature, and
actions taken were likely counterproductive. The opportunity to increase knowledge of the ecosystem was lost. Uninformed management
decisions, essentially “management by assertion,” undermine the long-term prospects for biodiversity conservation. 相似文献
44.
45.
46.
Tran D Massabuau JC Garnier-Laplace J 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):821-826
Multi-stress situations are a major question and low-oxygenated waters (hypoxia) are a growing problem. Importantly, hypoxia stimulates the ventilatory flow rate in aquatic animals and this increases gill exposure to contaminants. Surprisingly, in the freshwater clam Corbicula fluminea, this is associated with increased bioaccumulation of uranium in gills but not in deep tissues. We searched for an explanation by analyzing hemolymph U-transport in Corbicula exposed to 0.36 μM dissolved uranium at various O2-levels for 10 days. In hypoxia, one observed an increased U concentration in the arterial hemolymph flowing from gills to tissues but this was not associated with an increased U concentration in the venous hemolymph nor in the other tissues. We conclude that the cardiac flow rate must have decreased to explain this absence of over-accumulation. In addition to its already known deleterious effects, uranium can thus deeply impair cardiac flow rate in exposed aquatic animals during multi-stress exposures. 相似文献
47.
48.
Malaysia is facing an increase in the generation of waste and of accompanying problems with the disposal of this waste. In the last two decades, extensive building and infrastructure development projects have led to an increase in the generation of construction waste material. The construction industry has a substantial impact on the environment, and its environmental effects are in direct relation to the quality and quantity of the waste it generates. This paper discusses general characteristics of the construction contractors, the contractors' willingness to pay (WTP) for improved construction waste management, determining factors which affect the amount of their willingness to pay, and suggestions and policy implications in the perspective of construction waste management in Malaysia. The data in this study is based on contractors registered with the construction industry development board (CIDB) of Malaysia. Employing the open ended contingent valuation method, the study assessed the contractors' average maximum WTP for improved construction waste management to be RM69.88 (1US$=3.6 RM) per tonne of waste. The result shows that the average maximum WTP is higher for large contractors than for medium and small contractors. The highest average maximum WTP value is RM88.00 for Group A (large contractors) RM78.25 for Group B (medium-size contractors) and RM55.80 for Group C (small contractors). One of the contributions of this study is to highlight the difference of CIDB registration grade in the WTP for improved construction waste management. It is found that contractors' WTP for improved waste collection and disposal services increases with the increase in contractors' current paid up capital. The identified factors and determinants of the WTP will assist the formulation of appropriate policies in addressing the construction waste problem in Malaysia and indirectly improve the quality of construction in the country. 相似文献
49.
Diane Lefebvre Jacqueline Pierre Yannick Outreman Jean-Sébastien Pierre 《Behavioral ecology and sociobiology》2007,61(11):1707-1715
The patch living rules of a pollinator, the bumblebee Bombus terrestris L., are studied here in the framework of motivational models widely used for parasitoids: The rewarding events found during
the foraging process are supposed to increase or decrease suddenly the tendency of the insect to stay in the current patch
and therefore to adjust the patch residence time to the patch profitability. The foraging behaviour of these pollinators was
observed in two environment types to determine their patch-leaving decisions. The rich environment was composed of male-fertile
flowers, offering pollen and nectar, and the poor one of male-sterile flowers, offering little nectar and no pollen. The experimental
design consisted of a patch system in which inflorescences were evenly arranged in two rows (1 m distance). Residence times
of foragers inside inflorescences and rows were analysed by a Cox proportional hazards model, taking into account recent and
past experience acquired during the foraging bout. Most of the results showed a decremental motivational mechanism, that is,
a reduction in the residence time on the inflorescence or in the row related to exploitation of flowers within inflorescences
and inflorescences within rows These results indicate that bumblebees tend to leave the patch using departure rules similar
to those found in parasitoids. The results also provide information on the memory, learning and evaluating capabilities of
bumblebees especially when rich and poor environments were compared. The patch-leaving mechanism suggested by this study is
consistent with the central place foraging theory. 相似文献
50.
Phenology of mixed woody-herbaceous ecosystems following extreme events: net and differential responses 总被引:2,自引:0,他引:2
Ecosystem responses to key climate drivers are reflected in phenological dynamics such as the timing and degree of "green-up" that integrate responses over spatial scales from individual plants to ecosystems. This integration is clearest in ecosystems dominated by a single species or life form, such as seasonally dynamic grasslands or more temporally constant evergreen forests. Yet many ecosystems have substantial contribution of cover from both herbaceous and woody evergreen plants. Responses of mixed woody-herbaceous ecosystems to climate are of increasing concern due to their extensive nature, the potential for such systems to yield more complex responses than those dominated by a single life form, and projections that extreme climate and weather events will increase in frequency and intensity with global warming. We present responses of a mixed woody-herbaceous ecosystem type to an extreme event: regional-scale pi?on pine mortality following an extended drought and the subsequent herbaceous green-up following the first wet period after the drought. This example highlights how reductions in greenness of the slower, more stable evergreen woody component can rapidly be offset by increases associated with resources made available to the relatively more responsive herbaceous component. We hypothesize that such two-phase phenological responses to extreme events are characteristic of many mixed woody-herbaceous ecosystems. 相似文献