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531.
Gilles Billen Vincent Thieu Josette Garnier Marie Silvestre 《Agriculture, ecosystems & environment》2009,133(3-4):234
The watersheds of the Seine, Somme and Scheldt rivers (France, Belgium, the Netherlands), flowing into the continental coastal zone of the English Channel and Southern North Sea, are among the regions of the world with the highest anthropogenic inputs of reactive nitrogen through fertilizer use, legume fixation and deposition of atmospheric nitrogen. They also represent examples of widely open systems, either exporting a large fraction of their N inputs under the form of agricultural products (case of the Seine basin) or importing high amounts of nitrogen as feed for livestock nutrition (case of the Scheldt basin), and delivering up to 2000 kg N km−2 yr−1 at river outlet into the sea. Taking these three watersheds as a case study, we review the different approaches developed so far for describing and predicting the fate of reactive nitrogen inputs to regional systems and its cascade from soils to sea. These approaches range from simple lumped input–output budget, to detailed process-based, spatially distributed models of nutrient transfers. The merits and the limits of these approaches are discussed. Their combination allows to establish a reasonably consistent budget for the three basins, emphasizing the various ‘retention’ terms linked to both landscape and in-stream processes, including storage in long residence time compartments (soil organic matter, vadose zone, aquifers, etc.), denitrification (in soil, riparian zones or river benthos) or sediment burial. Root-zone and riparian denitrification processes appear as major terms of landscape retention in all three investigated watersheds. Retention of nitrogen associated with collection and treatment of urban wastewater is also a major term in the two most populated watersheds. 相似文献
532.
New Zealand has over 500 offshore islands. Many consist of relatively pristine wilderness and contain a disproportionately large amount of New Zealand's biological wealth. Increased demand for recreation has increased the pressure to develop these areas. Although the New Zealand public has shown widespread support for the preservation and safeguarding of both wilderness areas and endangered species, economic values attached to the benefits of preservation are not known. Using a telephone survey, we found evidence that the public attaches significant value to the conservation of Little Barrier Island. The results show that these values are influenced by different levels and sources of prior information. 相似文献
533.
F. Lynn Carpenter Mark A. Hixon Robert W. Russell David C. Paton Ethan J. Temeles 《Behavioral ecology and sociobiology》1993,33(5):297-304
Summary Three age-sex classes of rufous hummingbirds (Selasphorus rufus) overlap temporally and defend feeding territories during migratory stopovers in the Sierra Nevada of California. We demonstrate that these classes differ in their ability to secure and maintain high-quality feeding territories for refueling, and that these differences result in differences in resource use. Data on acquisition of territories, territory characteristics, and responses of territory owners to intruders suggest that several mechanisms are involved in determining dominance, involving sex- and age-related differences in wing disc loading, coloration, and experience. We discuss the implications of these results for understanding intraspecific variation in migration strategies.
Correspondence to: F.L. Carpenter 相似文献
534.
Clifford S Russell William J Vaughan 《Journal of Environmental Economics and Management》1974,1(1):17-42
This paper briefly describes a linear programming model designed to allow the exploration of questions surrounding the management of the environmental impacts of integrated iron and steel facilities. In particular, the model can show how plant discharges will change in the absence of specific legal restrictions or effluent charges, with such variables as product mix, steel-furnace type, casting technology, and the scrap-ore price ratio. In addition, the costs implied by placing restrictions on discharges of specific residuals (e.g., BOD, oil, suspended solids, particulates) may be estimated, or response to proposed effluent charges may be predicted. 相似文献
535.
Carty T. Chiou Rodger L. Kohnert Virgil H. Freed Russell G. Tonkyn 《Environment international》1983,9(1):13-17
A previously published kinetic model for evaporative rates of substances into air leads to the estimation of the dependence of solute transfer coefficients on turbulence to the system. The ratios of the transfer coefficients of all solutes become insensitive to air turbulence and to water mixing either when they have comparable Henry's law constants or when their Henry's law constants are sufficiently low, but not otherwise. Confirming data are presented and methods for simplifying the estimation of transfer coefficients are discussed. 相似文献
536.
Amy Pruden Marie A Sedran Makram T Suidan Albert D Venosa 《Water environment research》2005,77(3):297-303
The feasibility of biodegradation of the fuel oxygenate methyl tert-butyl ether (MTBE) under iron-reducing conditions was explored in batch and continuous-flow systems. A porous pot completely-mixed reactor was seeded with diverse cultures and operated under iron-reducing conditions. For batch studies, culture from the reactor was transferred anaerobically to serum bottles containing either MTBE alone or MTBE with ethanol (EtOH) and excess electron acceptor. In the continuous-flow reactor, MTBE conversion to tert-butyl alcohol (TBA) was observed after 181 days of operation, and stable removal was achieved throughout the remainder of the study. Simultaneously, both the MTBE only and the MTBE and EtOH iron-reducing batch serum bottles also began to degrade MTBE. Bottles were respiked and the degradation rate was determined to be 2.36 +/- 0.10 x 10(-4) mmol MTBE/min-kgVSS. The EtOH present with MTBE degraded faster (7.76 +/- 0.08 x 10(-3) mmol EtOH/min-kg VSS) but did not have a noticeable effect on the rate of MTBE degradation. No evidence of TBA degradation was observed by the iron-reducing cultures. Stoichiometry of iron utilization was determined from the iron balance of the continuous-flow reactor, and it was found that the bulk of the electron acceptor was required for energy and maintenance with little remaining for cell synthesis. This is consistent with a yield coefficient of less than 0.1. Molecular analysis of the iron-reducing culture by denaturing gradient gel electrophoresis indicated that uncultured strains of delta-Proteobacteria were dominant in the reactor. 相似文献
537.
Stickler syndrome or hereditary progressive arthro-ophthalmopathy, is an autosomal dominant condition characterized by ocular manifestations, arthritic changes, orofacial features and deafness, in variable degrees. We report the first case of prenatal diagnosis of Stickler syndrome in a child with a Pierre–Robin sequence (PRS) causing a polyhydramnios. When isolated polyhydramnios is not explained by immunological, metabolic or infectious causes, swallowing difficulty due to PRS must be considered. As PRS is aetiologically heterogenous, the prognosis depends on the cause. Genetic investigations and familial history must be taken into account. Here, in a context of familial Stickler syndrome, making the prenatal diagnosis of PRS as part of Stickler syndrome allowed us to reassure the parents and to anticipate airway trouble at the child's birth. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
538.
Ju-Chang Huang Russell L. Smith 《Journal of the American Water Resources Association》1974,10(5):942-951
ABSTRACT: Up to date there are still not many instances that can be found on the practice of a totally closed system of water supply, treatment, and reuse. In the United States, this is partly because the Public Health Service has discouraged such a practice. However, are there sound scientific reasons to support such a decision or is it purely a matter of psychological reason? Are the treatment technologies available today able to achieve the integrated closed system at a reasonable cost, yet without risking the public health? Are there some extra precautions that must be taken in practicing the direct reuse for the drinking purpose? These questions are discussed in this article. Current available technologies for advanced waste treatment are briefly reviewed and the treated effluent qualities obtained by the authors and others are used as a focal point of discussion on the feasibility of practicing the closed system. For this purpose, the treated effluent qualities are compared to the “Ranges of Promulgated Standards for Raw Water Sources of Domestic Water Supply” which have been used by the Public Health Service and several state regulatory agencies. 相似文献
539.
Russell Schoof 《Journal of the American Water Resources Association》1980,16(4):697-701
ABSTRACT: The purpose of this literature review is to identify and quantify the effects of channelization and to examine the feasibility and acceptability of alternative methods of flood control. In the past 150 years, over 200,000 miles of stream channels have been modified. Channelization can affect the environment by draining wetland, cutting off oxbows and meanders, clearing floodplain hardwoods, lowering ground water levels, reducing ground water recharge from stream flow, and increasing erosion sedimentation, channel maintenance, and downstream flooding. Channelization reduces the size, number, and species diversity of fish in streams. In a wet climate, the fishery requires less than 10 years to fully recover. However, in the drier climates, the fishery may never fully recover. In general, channel modifications have performed as designed for flood abatement. The Arthur D. Little Study (1973) reported that direct benefits estimated during channelization planning have been conservative and that damage reduction has been impressive. Diking seems to be a viable alternative to channel dredging. Dikes minimize destruction of wetland and eliminate the need for removing vegetation from the existing stream banks. 相似文献
540.
P. J. C. Russell 《Marine Biology》1972,16(4):290-296
The recent separation of Cardium glaucum Bruguière from C. edule L. and the scarcity of reports of populations containing both species has necessitated further ecological study to demonstrate differences in habitat preferences. Some mixed and unispecific populations of the cockles Cardium edule and C. glaucum, situated in fjords around the Kattegat and Baltic coasts of Denmark were studied; it was demonstrated that some degree of tidal influece was essential for the survival of C. edule, and that C. glaucum was being restricted by the exposure of the site. A study of the cockle populations of some étangs on the Mediterranean coast of France demonstrated that, despite earlier reports of its presence, C. edule was not present in that area. A brief survey of the Bassin d'Arcachon (France) showed that it contained a mixed cockle population. It was concluded that C. edule was unable to occupy localities having a tidal amplitude of less than 0.2 m, and that high temperatures also restricted occupation of semitidal habitats; similarly, the exposure of the site restricted colonisation by C. glaucum. 相似文献