共查询到20条相似文献,搜索用时 15 毫秒
1.
Kaye Nigel B. Robinson Dylan M. Akhter Romana Ahsanullah Md Safwan Jordan TaJon A. Martinez Oscar E. 《Environmental Fluid Mechanics》2022,22(4):763-787
Environmental Fluid Mechanics - Buoyant turbulent plumes are often categorized by their geometry and described as either round plumes, issuing from a point source, or line/planar plumes, issuing... 相似文献
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Dandan ZHOU Shuangshi DONG Keyu LI Huizhong JIANG Dandan SHANG 《Frontiers of Environmental Science & Engineering》2013,7(1):127-134
With the random movement of silica gel beads in a conical fluidized bed, micro-vortices resulting from the fluidization promoted the collision and aggregation of suspended fine kaolin powders. The abatement efficiencies of the suspended fine solids under several hydrodynamic conditions were studied, and a suitable control strategy for operating the conical fluidized bed flocculators was identified. The suspended solids abatement efficiency was found to increase with increasing Camp Number and flocculation time (T ), but decreased with the increase of velocity gradient (G ) within the range studied in this research (165.1–189.6 s-1). The abatement efficiencies were all more than 60% at the range of G = 165–180 s-1 and T = 15–33 s at an initial kaolin solid concentration of 150 mg·L-1, polymer aluminum chloride dosage of 60 mg·L-1 and sedimentation time of 20 min. However, the formation of flocs was influenced by the liquid backmixing. Excessive backmixing caused the breakup of flocs and resulted in difficulty for the fine powders to aggregate and sediment to the reactor bottom. The results of the calculated fractal dimension and measured free sedimentation velocity of flocs obtained at different runs showed similar flocs properties, and indicated an easy control strategy for sedimentation of the flocs. 相似文献
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Environmental Chemistry Letters - Pillared interlayered clays have interesting properties such as high surface area, pore volume and extended pore size, high thermal stability, strong surface... 相似文献
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Despite proliferation of the use of air pollution models for regulatory application, major discrepancies still occur between models and also between models and observations, especially when oversimplistic models are used. The problem of predicting plume rise (and subsequently ground level concentrations) from a single source is evaluated here in terms of an integral plume rise and dispersion model (USPR) which encompasses both bouyant rise and turbulent spreading; thus avoiding the problems of the concatenation of separate plume rise and dispersion models. The wide range of validity of the USPR model is demonstrated is terms of plume rise by comparison with the highly buoyant GCOS and Kincaid plumes as well as with dense effluents. It is also shown to be in agreement with Briggs' two-thirds law when the restrictions applicable to the latter model are imposed. 相似文献
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The benthic response to a plume front was studied in two areas of the northern Adriatic (Mediterranean Sea) differently influenced
by the Po River freshwater input. Sediment samples were collected in June 1996 and February 1997 from 12 stations. The adopted
sampling strategy was able to identify the front line in real time by satellite images and to locate sampling stations along
an inner–outer plume gradient in order to cover the benthic area beneath the river plume, where enhanced biological production
was expected, and open-sea sediments not directly influenced by freshwater inputs. Meiofaunal parameters were compared to
the physical conditions and to phytodetritus inputs, organic matter accumulation and bacterial secondary production. The sediments
of the Adriatic Sea were characterised by high concentrations of phytopigments (0.6 to 13.9 μg g−1 for chlorophyll a and 1.2 to 17.7 μg g−1 for phaeopigments) and biopolymeric organic carbon (0.15 to 3.02 mg g−1). The plume system extended for a large sector of the northern Adriatic. In the northern area, a large and highly dynamic
plume area was coupled with a sediment organic matter concentration significantly higher than in open-sea sediments. In the
southern sector, where the plume area and the front line did not change markedly during the year, plume–benthic coupling was
evident only in the sediments beneath the front, and corresponded to phaeopigment accumulation. Bacterial parameters and secondary
production were high and significantly higher in the frontal area than at open-sea stations. Meiofauna density (1342 to 8541
ind. 10 cm−2) did not change either by season or between areas and was significantly correlated with phaeopigments and bacterial secondary
production. Meiofauna displayed different responses to plume inputs in the two sampling areas. In the northern sector, meiofauna
density was coupled with organic matter distribution and displayed highest values beneath the plume. In the southern sector,
the densities of copepods, turbellarians and kinorhynchs displayed highest values under the front in summer, and the same
applied to total meiofauna density in winter. Juvenile decapods and copepod nauplii significantly increased their densities
in sediments beneath the front. Data presented in the present study suggest that plume inputs and frontal systems, enhancing
phytodetritus accumulation and benthic bacterial response, might influence density, composition and distribution of meiofaunal
assemblages. As river plumes are highly variable systems affecting the trophic characteristics of the sediments underneath,
their dynamics should be considered when analysing mesoscale spatial changes of meiofaunal assemblages.
Received: 30 November 1999 / Accepted: 24 May 2000 相似文献
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Environmental Fluid Mechanics - A series of experiments were conducted to quantify the dynamics of a filling box driven by a line plume that spans the full width of the enclosure. Three... 相似文献
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Wenjing Lu Yawar Abbas Muhammad Farooq Mustafa Chao Pan Hongtao Wang 《Frontiers of Environmental Science & Engineering》2019,13(2):30
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Composition of a deep scattering layer overlying a mid-ocean ridge hydrothermal plume 总被引:1,自引:0,他引:1
Three sets of zooplankton trawls with multiple nets were deployed in June 1990 within a deep (2000 m) scattering layer overlying the central hydrothermal vent field on the Endeavour segment of Juan de Fuca Ridge in the northeast Pacific. Trawl data were collected concurrently with temperature, salinity, light attenuation and acoustic (150 kHz) backscatter profiles. We describe the composition, size distribution and biomass of zooplankton collected in the net samples, and compare biomass distributions with physical characteristics of the hydrothermal plume. The nine discrete trawl samples (1 mm mesh) contained zooplankton biomass of between 0.3 and 21 mg dry wt m-3 with the highest biomass samples coincident with large and positive (+20 dB) acoustic backscatter anomalies observed above the top of the hydrothermal plume. Lowest biomass samples were coincident with small, negative (-5 dB) backscatter anomalies within the core of the plume. Results suggest that the region within a hundred meters of the top of the plume was a zone of enhanced zooplankton concentration associated with nutrition enrichment related to the plume. In contrast, the plume core was a zone of faunal depletion, presumably linked to adverse plume chemistry. The species composition and size distribution profiles from net samples revealed that the epi-plume assemblage contained several trophic levels of bathypelagic fauna, but did not contain benthic larvae or vent-related benthopelagic fauna. 相似文献
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This paper provides a first analysis of a “policy bloc” of fossil fuel importers which implements an optimal climate policy, faces a (non-policy) fringe of other fuel importers, and an exporter bloc, and purchases offset from the fringe. We compare a carbon tax and a cap-and-trade scheme for the policy bloc, in either case accompanied by an efficient offset mechanism for reducing emissions in the fringe. The policy bloc is shown to prefer a tax over a cap, since only a tax reduces the fuel export price and by more when the policy bloc is larger. Offsets are also more favorable to the policy bloc under a tax than under a cap. The optimal offset price under a carbon tax is below the tax rate, while under a cap and free quota trading the offset price must equal the quota price. The domestic carbon and offset prices are both higher under a tax than under a cap when the policy bloc is small. When the policy bloc is larger, the offset price can be higher under a cap. Fringe countries gain by mitigation in the policy bloc, more under a carbon tax since the fuel import price is lower. 相似文献
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Environmental Fluid Mechanics - Two recently reported models, the Virtual Variance Sources (VVS) model and the Volumetric Particle Approach (VPA), both predicting the second moment of passive... 相似文献
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Gut fullness of larval fishes was used to determine the nutritional significance of an estuarine plume front off Botany Bay, SE Australia, on three days in March/April 1990. Fishes were captured in three different water masses (estuarine plume, front and shelf water), each separated by 200 m, using a 260 m mesh purse-seine net. Overall, the gut-fullness index (GFI) of 260 fish larvae combined from eight families (Gerreidae, Mugilidae, Mullidae, Sparidae, Blenniidae, Kyphosidae, Monodactylidae, Pomacentridae), was significantly greater in the plume and front water on two of the sampling occasions, but no difference was detected on the third occasion. Trends in GFI among families were inconsistent with respect to the front. The mugilid (Liza argentea) fed equally and abundantly in all water masses (gut fullness>90%), while the kyphosid (Kyphosus spp.) had a significantly greater GFI in the plume compared to the shelf water. In general, the response of GFI to the front varied between dates and amongst taxa. Diet analysis showed that mugilids selected for copepod nauplii within the plume and shelf water [alpha selectivity index (ASI) of (0.22 to 0.98)] and for harpacticoid copepods within the front (ASI=0.92), representing characteristic diets identified by canonical discriminant analysis. Kyphosids selected positively for copepod nauplii in all three water masses on both occasions (ASI>0.96). In general, diets of larval fish were taxon-specific, and responded variably to the three habitats. Comparison of diets across water masses was complicated by the large number of families, which rarely occurred in all water masses. The nutritional significance of an estuarine plume front varies between species of larval fish, and there are no obvious trends that can be applied to the larval fish community in general. 相似文献
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This paper extends earlier work on the standards and prices approach to pollution control by considering simultaneously spatial considerations, interactive pollutants, and joint abatement costs. The form of environmental constraints appropriate to water pollution problems is discussed in detail and the implications for the standards and prices approach to water pollution control are assessed. The presence of interactive pollutants and joint abatement costs is shown to have important implications for both the theoretical properties and the implementation of the standards and prices approach. 相似文献
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Environmental Fluid Mechanics - Analytical solutions are developed for the flow induced by a vertically distributed turbulent plume in an otherwise quiescent uniform environment. The plume... 相似文献
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生态系统服务研究的问题与展望 总被引:1,自引:0,他引:1
生态系统服务的研究是当前资源经济学和生态经济学的研究热点之一。通过分析生态系统服务的概念辨析,认为从生态系统功能的定义过渡到生态系统服务定义的过程中,在关注生态系统整体性的同时忽略了生态系统要素之间的相互作用,导致生态系统服务的评估中可能存在着重复估值或者估值不全面等风险。针对目前的很多生态系统的评估对生态系统的耗损贬值和环境退化所造成的负效益的忽略,以及对人类活动的干扰和气候变化等对生态系统服务产生影响研究不足,提出在今后的研究中应该在深入理解生态系统的复杂生态学机制的基础上,结合数学模型模拟在不确定性下的各种风险损失,加强对生态系统服务的时空动态分析,重视在气候变化、经济发展、环境污染、城市化以及人类活动的过度放牧和过度开垦引起的水土流失、环境退化、荒漠化等土地利用变化的干扰时生态系统服务的变化和反馈,更进一步分析和预测生态系统服务的损益和响应研究;通过长期的试验监测揭示生物多样性和生态系统的关系,测度出土地利用和环境变化对生物多样性的影响和边际效益,及其对生态系统服务的影响的弹性值,实现生态系统服务的精确估值;关注生态系统服务对人类福利的影响,尤其重视贫困地区和生态脆弱区的生态系统服务对减小贫困的研究,建立科学的生态补偿机制,实现可持续发展。 相似文献
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Environmental Chemistry Letters - Microwave irradiation has been intensively studied for environmental remediation, e.g., for wastewater treatment, and for synthesis, to take advantages of the... 相似文献
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Organophosphorous compounds (OP) have largely been used as pesticides globally. These chemicals induce oxidative stress as a possible mechanism of action, which has been a focus of toxicological research for the last decade. This review evaluated the presence of oxidative stress, balance between total antioxidant capacity, and oxygen free radicals associated with OP compound exposure. Oxidative stress induced by OP leads to disturbances in function of different organs and tissues. Evidence indicates that stimulation of free radical production, induction of lipid peroxidation, and disturbance of the total antioxidant capacity are mechanisms of toxicity induced by most OP. Thus, use of antioxidants may be beneficial in treatment of OP poisoning, which remains to be elucidated with further clinical trials. 相似文献
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Industrial SO2 is the most important air pollutant in China. This paper outlines the technological impacts on industrial SO2 emissions in China in terms of: amount, intensity, structure of energy consumption and structure of energy-intensive industries. It shows that industrial SO2 emissions have linear growth alongside increases in energy consumption, particularly the rise in coal consumption. The contribution of technological factors to decreases in the intensity of energy consumption is 25%, while the structural factor is 75%. The power industry accounts for 52.6% of total industrial SO2. Optimisation of the structure of energy consumption can reduce SO2 emissions by 1.98 million tonnes per year. We propose the following technological strategies for industrial SO2 abatement: adjustment of the system and structure of thermal power generating units, acceleration of flue gas desulphurisation projects, transformation of industrial structures, development of eco-industries and a reduction in energy consumption per unit product. In addition, an effective way to abate industrial SO2 emissions is to promote governance strategies to stricly enforce SO2 emission standards, conduct emission trading, and formulate incentives for encouraging cleaner production and clean energy development. 相似文献