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221.
Rafael A. Kascheev 《Earth, Moon, and Planets》1988,41(1):89-94
A new approach is discussed for determination of lunar gravity parameters. Estimations were made with the line-of-sight (LOS) accelerations of artificial satellites. Tests indicate the advantages of such an approach over the classical one. 相似文献
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Large-scale fields of soil moisture are forced by atmospheric precipitation and radiative forcing. When these forcing factors
are themselves influenced by surface and soil moisture processes, the result is a nonlinear land-atmosphere system with inherent
feedback mechanisms that may strongly modulate variability in climate. Given such feedbacks, simple randomness in the forcing
factors may be manifested as a complex statistical signature in the surface hydrology. In this paper, we investigate the impacts
of non-Gaussian and colored-noise on the probability distribution of soil moisture resulting from the statistical-dynamical
land-atmosphere interaction model of Rodriguez-Iturbe et al. (1991). Persistence of hydroclimatologic anomalies as characterized
by the correlation time scale of soil moisture is discussed. 相似文献
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Rafael Prez-Lpez Antonio M. lvarez-Valero Jos Miguel Nieto Reinaldo Sez Joo X. Matos 《Applied Geochemistry》2008,23(12):3452-3463
São Domingos is one of the most emblematic Portuguese mining districts in the Iberian Pyrite Belt (IPB). The beginning of mining exploitation in the area has been dated back to pre-Roman times, remaining in activity until 1966 when it was definitely halted. The intense mining labours are reflected in the presence of a huge amount of sulphide-mining wastes and downstream production of acid mine drainage (AMD). The mining wastes in the area are highly heterogeneous, and numerous different types may be recognized, including slags, iron oxides, smelting ashes, brittle and blocks of pyrite, leaching tank refuses, industrial landfill and other residues coming from ore extraction (gossan wastes and country rocks). The chemical speciation of potentially toxic elements (As, Cd, Cr, Cu, Fe, Mn, Pb, S, Sb and Zn) in all mine wastes from São Domingos was determined by modified BCR-sequential extraction procedure (European Community Bureau of Reference) and combined with the mass/volume proportions of each waste to quantify the potential risk of this mining district at regional scale. Analytical recoveries by sequential extraction, with respect to a pseudo-total metal content digestion, were generally acceptable (100 ± 17%). The oxidizable fraction corresponds with metals bound to sulphides and released easily under oxidizing conditions in AMD production processes. This is the most polluting fraction for the environment in this type of residues. Part of this fraction is retained by precipitation of soluble secondary minerals in warm periods, moving to the bio-available fraction that is dissolved in rainy periods. Just considering the bio-available fraction, all mine wastes from São Domingos may leach up to 172514 ton of Fe, 10564 ton of S, 6644 ton of Pb, 2610 ton of Zn, 1126 ton of Mn, 1032 ton of Cu, 183 ton of Cr, 109 ton of As, 34 ton of Sb and 0.9 ton of Cd. The process of precipitation and re-dissolution of efflorescent salts formed directly by oxidation of the oxidizable fraction is seasonally repeated, which causes an annual self-feeding and releasing of the bio-available fraction. Thus, the present study shows the pollutant potential of this IPB mining district and explains the spoiled state of the fluvial courses in the region. 相似文献
229.
Francisco Padilla Ana Méndez Rafael Fernández Pablo R. Vellando 《Environmental Geology》2008,55(1):215-226
This applied research deals with the numerical modelling and transient simulation of the joint surfacewater/groundwater flows
that characterize the freshwater/saltwater hydrology of the coastal alluvial valley of the Low Guadalhorce River, Malaga,
Spain. The MELEF model used was mainly adapted and calibrated for a simulation period of two hydrological years 1989/1990–1990/1991,
before the current channelling of the river, where floods and low precipitations have been recorded. The model calibration
process was performed with the aid of phreatic levels measured in numerous wells and piezometers, as well as recharges from
precipitation and irrigation on the alluvial surface, which was also assessed by the hydrologic model SSMA-2. The present
numerical approach can predict the forthcoming hydrology of the coastal alluvial of the Guadalhorce River after its final
channelling. 相似文献