The Sea Empress oil spill (Wales, UK): effects on Common Scoter Melanitta nigra in Carmarthen Bay and status ten years later     

Banks AN  Sanderson WG  Hughes B  Cranswick PA  Smith LE  Whitehead S  Musgrove AJ  Haycock B  Fairney NP 《Marine pollution bulletin》2008,56(5):895-902

Carmarthen Bay, UK, regularly supports internationally important numbers (>16,000) of non-breeding Common Scoters Melanitta nigra. The spill of 72,000 tonnes of crude oil from the Sea Empress in 1996 affected birds both through direct mortality and likely pollution of key food resources. Numbers were greatly reduced following the spill, whilst changes in the distribution of birds within Carmarthen Bay suggested that potentially sub-optimal foraging zones were used. However, ten years after the incident, numbers of Common Scoter were no different to those recorded immediately before the spill. Compared to some other spills, rapid revival is evident. Numbers increased to pre-spill levels within three winters and distributional changes suggested a concurrent return to previously contaminated feeding areas, implying that the ecosystem had regenerated sufficiently to support its top predator. The importance of prolonged, standardised monitoring of bird numbers and distribution as indicators of ecological recovery from environmental damage is emphasised.  相似文献   

Intermediate-metallicity, high-velocity stars and Galactic chemical evolution   总被引：2，自引：0，他引：2  

S. G. Ryan  I. M. Smith 《Monthly notices of the Royal Astronomical Society》2003,341(1):199-212

High signal-to-noise ratio spectra were obtained of 10 high-proper-motion stars having  −1 ≲[Fe/H] < 0  , and a comparable number of disc stars. All but two of the high-proper-motion stars were confirmed to have  [Fe/H] > −1.0  , some approaching solar metallicity, but, even so, earlier measurements overestimated the metallicities and velocities of some of these stars. Models of stellar populations were used to assign membership probabilities to the Galactic components to which the high-velocity stars might belong. Many were found to be more probably thick-disc than halo objects, despite their large space motions, and two might be associated with the inner Galaxy. It may be necessary to reassess contamination of previous halo samples, such as those used to define the metallicity distribution, to account for contamination by high-velocity thick-disc stars, and to consider possible subcomponents of the halo.
The change in [α/Fe] ratios at  [Fe/H]≃−1.0  is often used to constrain the degree and timing of Type Ia supernova nucleosynthesis in Galactic chemical-evolution models. [Ti/Fe] values were measured for eight of the high-velocity stars. Both high- and low-[Ti/Fe] halo stars exist; likewise high- and low-[Ti/Fe] thick-disc stars exist. We conclude that the [Ti/Fe]'break' is not well defined for a given population; nor is there a simple, continuous evolutionary sequence through the break. Implications for the interpretation of the [α/Fe] break in terms of SN Ia time-scales and progenitors are discussed. The range of [Ti/Fe] found for high -velocity (low rotation) thick-disc stars contrasts with that for the low -velocity (high rotation) thick-disc sample studied by Prochaska et al.  相似文献   

Red giant branch in near-infrared colour–magnitude diagrams – I. Calibration of photometric indices     

E. Valenti  F. R. Ferraro  L. Origlia 《Monthly notices of the Royal Astronomical Society》2004,351(4):1204-1214

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The probability of detecting first generation stars of the Galaxy     

Cen Min-rui  Lu Ye  Zhao Gang 《Chinese Astronomy and Astrophysics》2001,25(4):432-438

First generation stars are the oldest stars that were formed in post-big bang, primitive gas, containing no elements heavier than carbon, with ages greater than 14 Gyr and having undergone no evolution so far. Observations over a long time have confirmed that, up to now, no stars with zero metallicity ([Fe/H]) or with [Fe/H]≤ −6 have been found in the Galaxy. To explain this absence, we shall make a theoretical calculation of the probability of detecting first generation stars using Tsuiimoto et al.'s model of chemical evolution of the galactic halo and assuming an initial mass function of the Miller-Scalo form. We use all the observational data on the halo stars to constrain the parameters. Our result is that, if the mass of the cloud that formed the stars is 10⁶–10⁷ M, then the probability of detecting first generation stars is 6.14×10⁻⁴–6.14×10⁻⁵.  相似文献   

Metrics for the comparative analysis of geospatial datasets with applications to high-resolution grid-based population data     

Aarthy Sabesan  Kathleen Abercrombie  Auroop R. Ganguly  Budhendra Bhaduri  Eddie A. Bright  Phillip R. Coleman 《GeoJournal》2007,69(1-2):81-91

Geospatial data sciences have emerged as critical requirements for high-priority application solutions in diverse areas, including, but not limited to, the mitigation of natural and man-made disasters. Three sets of metrics, adopted or customized from geo-statistics, applied meteorology and signal processing, are tested in terms of their ability to evaluate geospatial datasets, specifically two population databases commonly used for disaster preparedness and consequence management. The two high-resolution, grid-based population datasets are the following: The LandScan dataset available from the Geographic Information Science and Technology (GIST) group at the Oak Ridge National Laboratory (ORNL), and the Gridded Population of the World (GPW) dataset available from the Center for International Earth Science Information Network (CIESIN) group at Columbia University. Case studies evaluate population data across the globe, specifically, the metropolitan areas of Washington DC, USA, Los-Angeles, USA, and Houston, USA, and London, UK, as well as the country of Iran. The geospatial metrics confirm that the two population datasets have significant differences, especially in the context of their utility for disaster readiness and mitigation. While this paper primarily focuses on grid based population datasets and disaster management applications, the sets of metrics developed here can be generalized to other geospatial datasets and applications. Future research needs to develop metrics for geospatial and temporal risks and associated uncertainties in the context of disaster management. The U. S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.  相似文献   

Linguistic segregation in urban South Africa, 1996     

A.J. Christopher 《Geoforum》2004,35(2):145-156

South Africa is a multi-lingual country with 11 official languages and a recent history where language was frequently used as a political instrument, notably in the urban areas. Although the cities were initially colonial foundations, as a consequence of rural-urban migration, the speakers of the various national languages have come into close contact with one another. However, as a result of the inheritance of apartheid town planning and its emphasis on racial zoning, residential segregation levels between some linguistic groups have been extremely high. An analysis of the 1996 census results reveals that the uniformly high segregation levels between the speakers of indigenous African languages and the speakers of Afrikaans and English are the direct outcome of apartheid era town planning. Nevertheless, segregation between the speakers of different African languages may also on occasion be relatively high where homeland political policies were pursued, although this was the exception rather than the rule. Similarly segregation between English and Afrikaans speakers was locally high where home language coincided with former racial classification. Few immediate significant changes are anticipated in the present patterns of linguistic segregation, as the inherited apartheid city structure is proving to be remarkably resistant to transformation.  相似文献   

Population Growth of Zooplankton (Rotifers and Cladocerans) Fed Chlorella vulgaris and Scenedesmus acutus in Different Proportions     

J. Flores‐Burgos  S. S. S. Sarma  S. Nandini 《洁净——土壤、空气、水》2003,31(3):240-248

In the present work we tested the effect of Chlorella vulgaris and Scenedesmus acutus in different proportions on the population growth of Brachionus calyciflorus, Brachionus patulus, Ceriodaphnia dubia, and Moina macrocopa. In general, both rotifer species grew well on either type of algae. Regardless of algal mixture, B. calyciflorus had a shorter initial phase, while B. patulus needed more than a week to begin the exponential phase of growth. Both the rotifer species showed consistently better population growth with Chlorella than on Scenedesmus, or the mixture. At any given algal combination, B. patulus had higher peak values than B. calyciflorus. The rate of population increase (r) for both the rotifers varied from 0.18 to 0.48 d^—1 depending on the algal type and combination. Regardless of algal type and combination, B. calyciflorus had a much higher value of r than B. patulus. Both C. dubia and M. macrocopa grew on the algal types, whether offered separately or in mixture. Regardless of the treatment type, C. dubia needed a longer period (about 2 weeks) than M. macrocopa to reach peak abundances. Thus, our study did not support the view that Scenedesmus is consistently superior to Chlorella as a basic diet to the tested species of zooplankton.  相似文献   

Economics of Flood Protection in India     

Gupta  Sujata  Javed  Akram  Datt  Divya 《Natural Hazards》2003,28(1):199-210

The peculiar rainfall pattern in Indiarenders the country highly vulnerable to floods. Forty million hectares of land, roughlyone-eighth of the country's geographical area, is prone to floods. Each year, floods cause extensive damage to life and property, losses being exacerbated by rapid population growth, unplanned development and unchecked environmental degradation. The country has been tackling the problem through structural and non-structural measures. While non-structural measures like flood forecasting aim at improving the preparedness to floods by seeking to keep people away from floodwaters, structural measures involve the construction of physical structures like embankments, dams, drainage channels, and reservoirs that prevent floodwaters from reaching potential damage centres. Almost 48% of the vulnerable area has been provided with reasonable protection, though floods continue to cause widespread losses year after year. This paper examines the incidence of floods and the trends in consequent losses in the eastern region of the country – one of the most vulnerable – with the objective of studying the efficacy of flood protection measures in the region. Based on a simple regression exercise for three highly vulnerable states in the region, the paper argues that flood protection measures have been inadequate in controlling losses and reducing vulnerability. Regressions for the three states over the period 1971 to 1996 indicate that the level of protection is an insignificant explanatory variable in explaining the number of people (adjusted for increases in density) affected by floods; while area affected, as an indicator of the intensity of floods remains the main loss-determining factor.  相似文献   

Chemistry of springwater in Almora, Central Himalaya, India     

K. Kumar  D. S. Rawat  R. Joshi 《Environmental Geology》1997,31(3-4):150-156

 A field study was conducted to assess variations in physico-chemical characteristics of water of the springs located within the boundary of a Central Himalayan town where the springwater is used for drinking purposes. Monitoring of 12 springs was carried out for three seasons (winter, summer and monsoon). The results indicate direct influence of unplanned sewage disposal on the springwater quality as reflected by significant regional variations in the concentration of nitrates, chlorides, sulfates, sulfides and electrical conductivity. Population density varies within the town from 3110 to 14 137 persons/km^–2 and has direct relationship with water quality. Springs located in the densely populated area had higher concentrations of all these compounds. Concentrations of nitrates up to 60 ppm were observed in some springs, making water unsuitable for human consumption. No significant changes were observed in springwater quality during different seasons. Received: 3 February 1995 · Accepted: 27 February 1996  相似文献   

Modeling population density across major US cities: a polycentric spatial regression approach   总被引：3，自引：0，他引：3  

Daniel A. Griffith  David W. Wong 《Journal of Geographical Systems》2007,9(1):53-75

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