Heavy metal mobility assessment in sediments from the Odiel River (Iberian Pyritic Belt) using sequential extraction   总被引：1，自引：1，他引：0  

Rafael Beltrán  J. D. de la Rosa  J. C. Santos  M. Beltrán  J. L. Gómez-Ariza 《Environmental Earth Sciences》2010,61(7):1493-1503

The Tessier sequential extraction scheme (SES) was applied to sediments from the Odiel river catchment (Iberian Pyritic Belt, SW of Spain), one of the most acid rivers on Earth, to assess the chemical association (exchangeable, carbonatic, bound to manganese and iron oxides, bound to organic matter and residual mineral) of heavy metals (Zn, Cd, Pb, Cu, Cr, Mn, Ni, Fe, and Hg). Sediments are very heterogeneous in their textural characteristics, showing different grain size. Twenty-seven samples were studied from from areas along the Odiel River, from the source to the mouth, with special interest in the Odiel Marshes Natural Park due to its ecological significance. Samples were classified as sandy (especially at the river mouth with low iron oxide and organic matter content) and clay-silty (in the middle of the river catchment with high iron oxide content). The numerous sandy samples with low pH values explain the low levels of metals upstream, although potential metals contributions arise from mining and ore. However, the presence of sulfate in the mining area and carbonate at the mouth may explain the high presence of lead and iron in these sandy zones. Some percentage of mobile Ni, Cu, and Zn were detected in the mining area, but the elevated relative percentage of exchangeable Cd in the estuary is even more remarkable. The percentage of Zn bound to carbonate is considerable in the catchment but especially in the estuary. However, Cu is only detected in the carbonate phase downstream, in spite of the low concentration of carbonate, which represents a drawback in the application of the Tessier SES to these types of samples. Finally, relatively high percentages of residual, non-mobile, Hg and Pb were observed, in the estuarine and mining areas, respectively. Sand, lime, and clay fractions of representative samples from Areas I, II, and III were used in a metal speciation study. Mainly, the elements analyzed had accumulated in the non-residual fractions. In the mining area of the Pyrite Belt, the elements analyzed are mainly bound to Fe–Mn oxides (Fe + Mn + Cu + Cr + Pb + Mn ± Zn) and the organic matter/sulfide fraction (Ni + Zn + Hg ± Cd), independent of sediment grain size. In conclusion, we show that the results of the study of chemical speciation in sediments from acid rivers are independent of the sediment grain size considered.  相似文献   

Dynamics of contaminants in phosphogypsum of the fertilizer industry of Huelva (SW Spain): From phosphate rock ore to the environment     

Rafael Pérez-López  José Miguel Nieto  Israel López-Coto  Juan Luis Aguado  Juan Pedro Bolívar  María Santisteban 《Applied Geochemistry》2010

The dynamics of trace elements from phosphate rock ore to the environment in a phosphoric acid plant located in SW Spain and the impact of phosphogypsum wastes were investigated through total digestion and BCR-sequential extraction. Based on total concentration, element transfer factors as criteria for examining the potential environmental risk of waste with respect to ore rock were calculated, and it was observed that most trace elements are only transferred into phosphogypsum at rates of 2–12%. However, based on those concentrations that are likely to be most readily mobile in the environment, phosphogypsum acts as a higher emission source of contaminants than the original rock. About 100 million tonnes of phosphogypsum are stack-piled in a dump of 1200 ha over salt-marshes of an estuary formed by the confluence of the Tinto and Odiel rivers. Phosphogypsum has been applied, at the recommended rate of 20–25 t/ha since 1978–2001, to improve fertility and reduce Na saturation in agricultural soils of the Guadalquivir river valley (140 km²). Phosphogypsum capacity as a source of mobile contaminants in three environmental scenarios (water leaching, exposure to oxidising and reducing conditions) was quantified by combining sequential extraction and waste mass. The amounts of mobile contaminants that could be released for every tonne of phosphogypsum are approximately 7 × 10² g Sr, 1.1 × 10² g Fe, 55 g Y, 30 g Ce, 12 g Cr, 11 g Ti, 5 g Zn, 4 g each of Cu and Pb, 3 g each of V and Cd, 2 g each of As and Ni and 1 g U. Multiplying these amounts by 100 Mt and 20–25 t/ha, it is possible to calculate risk assessments of phosphogypsum for both estuarine zones, e.g. in a hypothetical stack collapse and waste spilling, and agricultural soils, respectively.  相似文献   

Common-offset common-reflection-surface attributes estimation with differential evolution     

Tiago Barros  Renato Lopes  Rafael Krummenauer  Hervé Chauris 《Geophysical Prospecting》2019,67(8):2022-2034

Common-reflection surface is a method to describe the shape of seismic events, typically the slopes (dip) and curvature portions (traveltime). The most systematic approach to estimate the common-reflection surface traveltime attributes is to employ a sequence of single-variable search procedures, inheriting the advantage of a low computational cost, but also the disadvantage of a poor estimation quality. A search strategy where the common-reflection surface attributes are globally estimated in a single stage may yield more accurate estimates. In this paper, we propose to use the bio-inspired global optimization algorithm differential evolution to estimate all the two-dimensional common-offset common-reflection surface attributes simultaneously. The differential evolution algorithm can provide accurate estimates for the common-reflection surface traveltime attributes, with the benefit of having a small set of input parameters to be configured. We apply the differential evolution algorithm to estimate the two-dimensional common-reflection surface attributes in the synthetic Marmousi data set, contaminated by noise, and in a land field data with a small fold. By analysing the stacked and coherence sections, we could see that the differential evolution based common-offset common-reflection surface approach presented significant signal-to-noise ratio enhancement.  相似文献   

Seismic response of multi-layered basins with velocity gradients upon incidence of plane shear waves     

Yong Zeng  Rafael Benites 《地震工程与结构动力学》1998,27(1):15-28

A boundary integral scheme based on boundary-integral discrete-wave-number approach has been developed to compute the seismic response of two-dimensional irregular-shaped basins with horizontal soil layers. Each layer exhibits a linear gradient of shear wave velocity with depth. The approach combines the boundary-integral representation of the seismic wave field outside the basin with plane wave representation of the seismic wave field inside the basin. The propagation throughout the layers is performed by matrix propagators in which the effect of the vertical variation of the velocity is incorporated by using confluent hyper-geometric functions of the Whittaker type. Our method is tested against otherwell-accepted solutions for the case of a circular basin with excellent agreement. Test of the ground response for a semi-circular basin with radius a shows that stable solutions are obtained if the chosen model parameters satisfy following conditions: (1) the distance from the sources to the interface is greater than 0·1a; (2) the distance between the sources is smaller than a quarter of the incident wavelength; and (3) the discrete wave-number step is smaller than 2π/4a. The computation of ground response of basins with a sharp interface and several horizontal deposits leads to the following main results: (1) the amplification of a basin with velocity gradients is larger than that of a basin with homogeneous layers; (2) the frequencies of the second- and third-order harmonics for a basin with velocity gradients are lower than those of a basin with homogeneous layers; and (3) the response amplitude of the basin with velocity gradients attenuates more slowly in time domain than when layers are homogeneous. Since these results have been obtained for realistic values of basin geometrical and mechanical consideration, they should find some interest in earthquake engineering or seismic microzonation studies. © 1998 John Wiley & Sons, Ltd.  相似文献   

Status of the science instruments and their detector plans at the giant magellan telescope     

Gustavo A. Rahmer  Rafael Millan-Gabet 《Astronomische Nachrichten》2023,344(8-9):e20230079

  相似文献   

Composition,Technology of Manufacture,and Circulation of Hellenistic Pottery from the Eastern Adriatic: A Case Study of Three Archaeological Sites along the Dalmatian Coast,Croatia     

Branimir &#x;egvi&#x;  Lucijana &#x;e&#x;elj  Damir Slovenec  Bo&#x;ko Lugovi&#x;  Rafael Ferreiro Mhlmann 《Geoarchaeology》2012,27(1):63-87

Archaeological excavations in Dalmatia have yielded a large amount of Hellenistic pottery that has yet to be archaeometrically analyzed. Stylistic analyses suggest that some vessels were imported, but the bulk of the material must have been produced locally. Our objectives are to demonstrate local ceramic production in both Greek colonies and native settlements in Dalmatia, and also to report on the composition and manufacture technology associated with this pottery. We examine 36 Hellenistic potsherds recovered from the coast of Croatia: a sanctuary on Cape Ploča, the native settlement of Resnik, and the Greek colony Issa. For the first time, archaeometric evidence supporting local production in Resnik is presented, while two local manufacturing centers are proposed for the bulk of the Cape Ploča pottery. The term Dalmatian production is suggested here to describe these indigenous ceramics. Material characteristics of the Issa samples suggest local colonial production and sophisticated ceramic technology.  相似文献