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排序方式: 共有371条查询结果,搜索用时 48 毫秒
91.
Resource Depletion and Sustainability in Small Open Economies 总被引:1,自引:0,他引:1
Jeffrey R. Vincent Theodore Panayotou John M. Hartwick 《Journal of Environmental Economics and Management》1997,33(3):274-286
Exogenous price changes affect the amount that a small country exporting natural resource commodities must invest to sustain its consumption level. The necessary amount is given by the difference between Hotelling rent and the discounted sum of future terms-of-trade effects (capital gains). The latter term is found to be large relative to the former in the case of petroleum depletion in Indonesia. This suggests that resource-rich countries will need to invest more than previously expected to sustain their consumption levels, if natural resource prices continue their long-term historical decline. 相似文献
92.
Summary. This study reports on the impact of insecticidal resistance on the diel periodicity of the calling behaviour and pheromone
production of different-aged virgin females of the obliquebanded leafroller (OBL), Choristoneura rosaceana. While both resistant (R) and susceptible (S) females initiated calling on the first night following emergence, the periodicity
of the calling behaviour, as determined by the mean onset time of calling (MOTC) and the mean time spent calling (MTSC) over
the first six nights of calling, differed between the two strains. R females started calling significantly later in the night.
However, as the MOTC of R females advanced with age but did not do so in S individuals, the difference between strains was
more pronounced in younger than older females. Furthermore, R females spent less time calling than S individuals. However,
the MTSC increased as a function of age in both R and S females, so the difference between strains remained fairly constant
for each night of calling. The major component of OBL sex pheromone, the Z11-14: Ac, determined at peak calling activity,
significantly declined with female age. Overall, pheromone production was lower in R females than in S females, with the difference
being more pronounced in younger than in older individuals. Thus, resistant females may have a lower mating success. The mating
success of both R and S strain males did not vary with the number of previous matings acquired. With regard to males, although
there was a significant decline in spermatophore size with successive matings, there was no significant difference between
strains. However, R males are smaller and may be disadvantaged through female choice and/or may respond differently to pheromone
source compared with S individuals. If the reproductive success of both sexes is affected, this may have a profound influence
on the dynamics of insecticidal resistance in the presence or absence of selection in OBL populations.
Received 4 July 2001; accepted 19 October 2001. 相似文献
93.
Amy M. Kahler Theresa L. Cromeans Maureen G. Metcalfe Charles D. Humphrey Vincent R. Hill 《Food and environmental virology》2016,8(2):148-155
It is generally accepted that viral particles in source water are likely to be found as aggregates attached to other particles. For this reason, it is important to investigate the disinfection efficacy of chlorine on aggregated viruses. A method to produce adenovirus particle aggregation was developed for this study. Negative stain electron microscopy was used to measure aggregation before and after addition of virus particles to surface water at different pH and specific conductance levels. The impact of aggregation on the efficacy of chlorine disinfection was also examined. Disinfection experiments with human adenovirus 2 (HAdV2) in source water were conducted using 0.2 mg/L free chlorine at 5 °C. Aggregation of HAdV2 in source water (≥3 aggregated particles) remained higher at higher specific conductance and pH levels. However, aggregation was highly variable, with the percentage of particles present in aggregates ranging from 43 to 71 %. Upon addition into source water, the aggregation percentage dropped dramatically. On average, chlorination CT values (chlorine concentration in mg/L × time in min) for 3-log10 inactivation of aggregated HAdV2 were up to three times higher than those for dispersed HAdV2, indicating that aggregation reduced the disinfection rate. This information can be used by water utilities and regulators to guide decision making regarding disinfection of viruses in water. 相似文献
94.
A.J. Khan Jianjun Li Vincent A. Dutkiewicz Liaquat Husain 《Atmospheric environment (Oxford, England : 1994)》2010,44(19):2364-2371
The effect of elemental carbon (EC) on global as well as regional climate forcing is potentially very important. However, the EC data for northeastern U.S. is sparse. Daily EC concentrations, [EC], and [SO4] were measured in the northeastern U.S. at a regionally representative rural site, Whiteface Mountain (WFM; 44.366°N, 73.903°W, 1.5 km amsl, above mean sea level), New York (NY), for 1997. The air mass origin was determined using 6-h backward in time air trajectories obtained from the Hybrid Single-Particle Lagrangian Integrated Trajectory Model (HYSPLIT 4). [EC] and [SO4] were highly variable and influenced by synoptic–scale meteorology (rainy vs dry periods). The maximum daily [EC] and [SO4] were 364 ± 55 and 28,800 ± 3000 ng m?3, respectively. [EC] and [SO4] also showed seasonal variations at WFM. Occurrences of high daily [EC] were mainly in spring months, while peak daily [SO4] concentrations occurred in summer months. This behavior of aerosols is due to the fact that the sources of EC and SO4 are not the same and also due to the enhanced photochemical activity during summer months that increased the production of SO4 from SO2. High [EC] and [SO4] values were associated with westerly air flow from the industrialized Midwestern U.S. Sector analysis using HYSPLIT 4 air trajectories showed that regions lying between the southwest and northwest of the WFM contributed 81% and 83% of the [EC] and [SO4], respectively. The monthly net direct radiative forcing for shortwave (SW) due to EC and SO4 aerosols at the top of the atmosphere (TOA) varied from ?0.05 to ?0.50 W m?2, with an annual average of ?0.20 ± 0.15 W m?2 that gives a net cooling effect. Average net radiative forcing at WFM for clear sky is lower than the global average radiative forcing reported by IPCC (Foster and Ramaswamy, 2007). 相似文献
95.
96.
Sebastien Humbert Yves Loerincik Vincent Rossi Manuele Margni Olivier Jolliet 《Journal of Cleaner Production》2009,17(15):1351-1358
This paper aims to evaluate the environmental burdens associated with spray dried soluble coffee over its entire life cycle and compare it with drip filter coffee and capsule espresso coffee. It particularly aims to identify critical environmental issues and responsibilities along the whole life cycle chain of spray dried coffee. This life cycle assessment (LCA) specifically uses foreground data obtained directly from coffee manufacturers and suppliers. Aside from energy consumption and greenhouse gases emissions, water footprint is also studied in detail, including regionalization of water impacts based on the ecological scarcity method 2006. Other impact categories are screened using the IMPACT 2002+ impact assessment method.The overall LCA results for a 1 dl cup of spray dried soluble coffee amounts approximately to 1 MJ of primary non-renewable energy consumption, to emissions of 0.07 kg of CO2-eq, and between 3 and 10 l of non-turbined water use, depending on whether or not the coffee cultivation is irrigated and wet treated. When considering turbined water, use can be up to 400 l of water per cup. Pouch – and to a lesser extent metal can packaging alternatives – show lower environmental burdens than glass or sticks.On average, about one half of the environmental footprint occurs at a life cycle stage under the control of the coffee producer or its suppliers (i.e., during cultivation, treatment, processing, packaging up to distribution, along with advertising) and the other half at a stage controlled by the user (shopping, appliances manufacturing, use and waste disposal). Key environmental parameters of spray dried soluble coffee are the amount of extra water boiled and the efficiency of cup cleaning during use phase, whether the coffee is irrigated or not, as well as the type and amount of fertilizer used in the coffee field. The packaging contributes to 10% of the overall life cycle impacts.Compared to other coffee alternatives, spray dried soluble coffee uses less energy and has a lower environmental footprint than capsule espresso coffee or drip filter coffee, the latter having the highest environmental impacts on a per cup basis. This study shows that a broad LCA approach is needed to help industry to minimize the environmental burdens directly related to their products. Including all processes of the entire system is necessary i) to get a comprehensive environmental footprint of the product system with respect to sustainable production and consumption, ii) to share stakeholders responsibility along the entire product life cycle, and iii) to avoid problem shifting between different life cycle stages. 相似文献
97.
Collecting marine organisms for the discovery and development of pharmaceuticals has been perceived variously as sustaining and threatening conservation. Our initial expectations that marine bioprospecting might pose conservation challenges were largely not confirmed. Thousands of marine species have been collected for initial assessment, but usually only in very small amounts. Very few compounds are sufficiently promising to provoke re-collections, where volumes can be much larger. This is where conservation concerns may arise, particularly if the organism is rare, has a restricted distribution, or is targeted in one narrow area. However, industry generally seeks to avoid dependency on small populations, for economic as well as ecological reasons. Alternative supply strategies to wild capture include synthesis and culture. Mandatory collection protocols and environmental impact (stock) assessments are useful routes for management to achieve sustainable use where extraction is desirable. In general, the scanty information available suggests that marine bioprospecting for pharmaceuticals may have minimal impacts on the environment, particularly compared with those created by other pressures. 相似文献
98.
Large variations exist in the size, abundance and biota of the two principal categories of freshwater ecosystems, lotic (flowing water; e.g., rivers, streams, deltas and estuaries) and lentic (standing water; lakes, ponds and wetlands) found across the circumpolar Arctic. Arctic climate, many components of which exhibit strong variations along latitudinal gradients, directly affects a range of physical, chemical and biological processes in these aquatic systems. Furthermore, arctic climate creates additional indirect ecological effects through the control of terrestrial hydrologic systems and processes, particularly those associated with cryospheric components such as permafrost, freshwater ice and snow accumulation/ablation. The ecological structure and function of arctic freshwater systems are also controlled by external processes and conditions, particularly those in the headwaters of the major arctic rivers and in the adjacent marine environment. The movement of physical, chemical and biotic components through the interlinked lentic and lotic freshwater systems are major determinants of arctic freshwater ecology. 相似文献
99.
Various types of ecosystem-based climate proxies have been used to assess past arctic change. Although lotic records are relatively poor because of the constant reworking of riverine material, high-quality lentic data have been assembled back to the end of the Pleistocene and deglaciation of the circumpolar Arctic. In general, climatic variations in the Holocene, partly due to changes in the shrinking effect of glacier coverage, produced significant temporal and spatial variations in arctic hydrology and freshwater ecosystems. Of particular note were the vast expansions of northern peatlands during major protracted periods of wetting. More recent lake biota and sedimentiological data reflect the general warming trend that has occurred over the last one to two centuries and indicate major changes to freshwater characteristics such as ice-cover duration and thermal stratification. Such data provide an excellent baseline against which future effects of climate change can be both projected and measured. 相似文献