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141.
Interaction of acid mine drainage with waters and sediments at the Corona stream, Lousal mine (Iberian Pyrite Belt, Southern Portugal) 总被引:1,自引:0,他引:1
E. Ferreira da Silva C. Patinha P. Reis E. Cardoso Fonseca J. X. Matos J. Barrosinho J. M. Santos Oliveira 《Environmental Geology》2006,50(7):1001-1013
This study investigates the geochemical characteristics of the acid mine drainage discharged from the abandoned mine adits and tailing piles in the vicinity of the Lousal mine and evaluates the extent of pollution on water and on the stream sediments of the Corona stream. Atmospheric precipitation interacting with sulphide minerals in exposed tailings produces runoff water with pH values as low as 1.9–2.9 and high concentrations of
(9,249–20,700 mg l−1), Fe (959–4,830 mg l−1) and Al (136–624 mg l−1). The acidic effluents and mixed stream water carry elevated Cu, Pb, Zn, Cd and As concentrations that exceed the water quality standards. However, the severity of contamination generally decreases 4 km downstream of the source due to mixing with fresh waters, which causes the dilution of dissolved toxic metals and neutralization of acidity. Some natural attenuation of the contaminants also occurs due to the general reduced solubility of most trace metals, which may be removed from solution, by either co-precipitation or adsorption to the iron and aluminium precipitates. 相似文献
142.
Rogrio L. Ferreira Filipe R. Ceia Teresa C. Borges Jaime A. Ramos Alan B. Bolten 《Marine Ecology》2021,42(1):e12636
Within the same population, nesting green turtles (Chelonia mydas) might exploit different niches by exhibiting polymorphic foraging strategies and/or inhabiting geographically distinct foraging areas. This is crucial information for the conservation of this species. Here, we used stable carbon and nitrogen isotope ratios (δ13C and δ15N) to test for differences in a population of green turtles nesting on Príncipe Island (1°37′N; 7°24?′E), Central Africa. A total of 60 nesting females were sampled on the two main nesting beaches of the island in December 2012. Minimum curved carapace length (CCL) was recorded, and δ13C and δ15N values were measured in the epidermis of each individual. Overall, CCL varied from 87.0 to 108.0 cm (mean ± SD =100.0 ± 5.1), δ13C values from ?19.4 to ?8.6‰ (?17.3 ± 1.8) and δ15N values from 7.9 to 17.3‰ (13.6 ± 1.5). Despite the large variation in both isotopic ratios, their distributions were unimodal, showing an absence of polymorphic foraging strategies and isotopically distinct foraging areas. However, smaller females (< median, 100.8 cm) occupied a much larger isotopic niche (i.e., four times greater) than larger females. These results suggest that nesting green turtles may forage opportunistically on the resources available in each of their foraging home ranges, with smaller females venturing to more isotopic‐diversified areas and/or exhibiting broader foraging strategies than larger females. In addition, and in accordance with other studies, findings suggest that the foraging grounds used by the Príncipe green turtle nesting females are distributed mainly throughout the Gulf of Guinea. 相似文献
143.
Siby Kurian Rajesh Agnihotri D. V. Borole S. Wajih A. Naqvi Ana M. Ferreira Carlos Vale 《第四纪科学杂志》2009,24(2):109-116
Using multiple geochemical proxies including specific biomarkers (dinosterol, phytol, stigmasterol and β‐sitosterol) measured in a high‐sedimentation rate core collected from the inner shelf (depth ~45 m) off Goa (India), we reconstruct surface productivity, which is mainly controlled by the monsoon upwelling in this region, during the last ca. 700 a. Surface productivity appears to have varied in tandem with the Konkan–Goa rainfall and sunspot activity during the instrumental period (last 250 a). The productivity proxies also covary with the total solar irradiance reconstructed for the period beyond the instrumental era, within the considerable uncertainty of the age model. This suggests that solar forcing may control coastal upwelling intensity and biological productivity in the eastern Arabian Sea on decadal to centennial timescales. During the late Anthropocene (last ca. 50 a), steep increases in all four biomarkers indicate greatly enhanced productivity in response to high solar irradiance as well as anthropogenic inputs of nutrients. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
144.
Darren M. O'Brien Paulo J.V. Garcia Jonathan Ferreira Sylvie Cabrit Luc Binette 《Astrophysics and Space Science》2004,292(1-4):609-617
The effects of phenomenological heating functions on the flow thermodynamics of cold T-Tauri disk winds are examined. Turbulent dissipation (mechanical) heating and a warm disk corona are invoked to heat the wind. The temperature and ionization evolution are solved for along the flow. The results allow the construction of synthetic observations; emission maps, forbidden line ratios, line fluxes and line profiles; and successfully reproduce a number of observed trends. Mechanical heating produces line ratios and fluxes that fit very well with observations. Invoking a warm disk corona successfully reproduces forbidden line profile low velocity components. 相似文献
145.
In this contribution, we first review the theory of self-collimated jets launched from magnetized accretion disks (disk-winds originating from the first AUs). We show why it is crucial to solve in a self-consistent way the interplay between the resistive accretion disk and the ideal MHD jets. Indeed, this is the only way to get exact values for the disk ejection efficiency ξ (the jet mass load issue). Then, we show self-similar calculations of such accretion-ejection structures: first cold jets, then warm jets obtained in the presence of a hot disk chromosphere. Finally, we present for the first time an accretion-ejection flow crossing all three critical points. 相似文献
146.
Marcel Marchand Agustin Sanchez-ArcillaMaria Ferreira Jeremy GaultJosé A. Jiménez Marina MarkovicJan Mulder Leo van RijnAdrian St?nic? Wojciech SuliszJames Sutherland 《Ocean & Coastal Management》2011,54(12):859-866
The main objective of the Conscience project was to develop and test concepts, guidelines and tools for the sustainable management of erosion along the European coastline, based on the best available scientific knowledge and on existing practical experience. Four concepts are potentially capable of providing the nexus between scientific knowledge and management: coastal resilience, coastal sediment cell, favourable sediment status and strategic sediment reservoir. The project has tested the use of these concepts and found that they are useful, provided that they are positioned and linked within a logical structure that we shall call the Conscience “Frame of Reference”, defined in time and space and supported through data and monitoring. Practical experience in six coastal sites in Europe has shown that the use of this Frame of Reference together with these concepts can make management objectives explicit and transparent. It can therefore support the design of an appropriate, resilience based coastal erosion management practice. 相似文献
147.
Jonathan Ferreira 《Astrophysics and Space Science》2004,293(1-2):83-90
The goal of this contribution is not to describe results on accretion discs launching jets obtained within the self-similar framework. Rather, I would like (1) to emphasize the huge difficulties one has to face when attempting to perform magnetohydrodynamic (MHD) numerical simulations of such discs; (2) to show how self-similar solutions can help to solve these difficulties. In particular, they allow to choose suitable boundary conditions and/or relevant initial conditions. In all cases anyway, they provide a framework for understanding and testing the outcome of numerical simulations. 相似文献
148.
149.
Michel Michaelovitch de Mahiques Samara Cazzoli y Goya Maria Carolina da Silva Nogueira de Matos Rodrigo Augusto Udenal de Oliveira Bianca Sung Mi Kim Paulo Alves de Lima Ferreira Rubens Cesar Lopes Figueira Marcia Caruso Bícego 《国际泥沙研究》2021,36(2):317-327
The current study aims to do a comparative analysis of the results obtained with two End-Member(EM)grain-size modeling techniques(AnalySize and BasEMMA)and the Environmental Sensitive Grain-Size(ESGS)modeling for sediment samples collected in the mudbelts of the southern Brazilian shelf.The methods were compared using grain-size data from the south Brazilian shelf,and the results are discussed here.It is the first time that the concept of ESGS,in its present form,is utilized outside China.The results show that despite its relative ease of use,the ESGS is not fully comparable to the EM analyses,and only two grain-size ESGS classes were recognized as analogous to EMs.The comparison of the AnalySize and BasEMMA procedures also revealed significant differences between the techniques.A comparative analysis between the two EM techniques revealed advantages in the BasEMMA,especially in the better correlation of the end-members with the original grain size distribution.The analysis of the geographical distribution of the EM abundances allowed point sources of sandy populations to be recognized as well as the contribution of the Rio de la Plata as a source of silty sediments to be inferred. 相似文献