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281.
Rafael J. de Moraes José R. P. Rodrigues Hadi Hajibeygi Jan Dirk Jansen 《Computational Geosciences》2018,22(6):1527-1541
A generic framework for the computation of derivative information required for gradient-based optimization using sequentially coupled subsurface simulation models is presented. The proposed approach allows for the computation of any derivative information with no modification of the mathematical framework. It only requires the forward model Jacobians and the objective function to be appropriately defined. The flexibility of the framework is demonstrated by its application in different reservoir management studies. The performance of the gradient computation strategy is demonstrated in a synthetic water-flooding model, where the forward model is constructed based on a sequentially coupled flow-transport system. The methodology is illustrated for a synthetic model, with different types of applications of data assimilation and life-cycle optimization. Results are compared with the classical fully coupled (FIM) forward simulation. Based on the presented numerical examples, it is demonstrated how, without any modifications of the basic framework, the solution of gradient-based optimization models can be obtained for any given set of coupled equations. The sequential derivative computation methods deliver similar results compared to FIM methods, while being computationally more efficient. 相似文献
282.
López-Moro F. J. López-Plaza M. Gutiérrez-Alonso G. Fernández-Suárez J. López-Carmona A. Hofmann M. Romer R. L. 《International Journal of Earth Sciences》2018,107(3):985-1004
International Journal of Earth Sciences - In this study, we report U–Pb Laser Ablation ICP-MS zircon and ID-TIMS monazite ages for peraluminous granitoid plutons... 相似文献
283.
Ramacciotti Carlos D. Casquet César Baldo Edgardo G. Galindo Carmen Pankhurst Robert J. Verdecchia Sebastián O. Rapela Carlos W. Fanning Mark 《International Journal of Earth Sciences》2018,107(7):2605-2625
International Journal of Earth Sciences - The Western Sierras Pampeanas (WSP) of Argentina record a protracted geological history from the Mesoproterozoic assembly of the Rodinia supercontinent to... 相似文献
284.
Estuaries act as an organic matter and nutrient filter in the transition between the land, rivers and the ocean. In the past, high nutrient and organic carbon load and low oxygen concentration made the Elbe River estuary (NW Europe) a sink for dissolved inorganic nitrogen. A recent reduction in loads and subsequent recovery of the estuary changed its biogeochemical function, so that nitrate is no longer removed on its transition towards the coastal North Sea. Nowadays in the estuary, nitrification appears to be a significant nitrate source. To quantify nitrification and determine actively nitrifying regions in the estuary, we measured the concentrations of ammonium, nitrite and nitrate, the dual stable isotopes of nitrate and net nitrification rates in the estuary on five cruises from August 2012 to August 2013. The nitrate concentration increased markedly downstream of the port of Hamburg in summer and spring, accompanied by a decrease of nitrate isotope values that was clearest in summer exactly at the location where nitrate concentration started to increase. Ammonium and nitrite peaked in the Hamburg port region (up to 18 and 8 μmol L?1, respectively), and nitrification rates in this region were up to 7 μmol L?1 day?1. Our data show that coupled re-mineralization and nitrification are significant internal nitrate sources that almost double the estuary’s summer nitrate concentration. Furthermore, we find that the port of Hamburg is a hot spot of nitrification, whereas the maximum turbidity zone (MTZ) only plays a subordinate role in turnover of nitrate. 相似文献
285.
Floriane Delpy Bruno Serranito Jean-Louis Jamet Gérald Grégori Christophe Le Poupon Dominique Jamet 《Estuaries and Coasts》2018,41(7):2039-2055
Due to its ecological context, the Toulon bay represents a site of scientific interest to study temporal plankton distribution, particularly pico- and nanophytoplankton dynamics. A monthly monitoring was performed during a two-year cycle (October 2013–December 2015) at two coupled sampling sites, referred to as Little and Large bays, which had different morphometric characteristics and human pressures. Flow cytometry analyses highlighted the fact that pico- and nanophytoplankton were more abundant in the eutrophic Little bay. Furthermore, it evidenced two community structures across the Toulon bays: at times, a co-dominance of picoeukaryotes, nanoeukaryotes, Synechococcus 1-like cells and Prochlorococcus-like cells was found, and at other times, a Synechococcus 1-like dominated community existed. The alternation of one structure or the other can be explained by a combined action of temperature regime, nutrient conditions and degree of contamination. This study showed that pico- and nanophytoplankton dynamics were mainly driven by temperature in both sites, as in other temperate Mediterranean regions. Thus, the community was mainly composed of picoeukaryotes and Prochlorococcus-like cells in the winter (<?15 °C), while it was dominated by Synechococcus 1-like cells in the summer (>?20 °C). Additionally, the multiple human stressors in the Little bay seemed to affect the increase in abundance of Synechococcus 1-like cells as they were preferentially observed in the Large bay. 相似文献
286.
Rainfall thresholds for the triggering of landslides considering previous soil moisture conditions (Asturias,NW Spain) 总被引:1,自引:0,他引:1
Pablo Valenzuela María José Domínguez-Cuesta Manuel Antonio Mora García Montserrat Jiménez-Sánchez 《Landslides》2018,15(2):273-282
Given its geological and climatic conditions and its rugged orography, Asturias is one of the most landslide prone areas in the North of Spain. Most of the landslides occur during intense rainfall episodes. Thus, precipitation is considered the main triggering factor in the study area, reaching average annual values of 960 mm. Two main precipitation patterns are frequent: (i) long-lasting periods of moderate rainfall during autumn and winter and (ii) heavy short rainfall episodes during spring and early summer. In the present work, soil moisture conditions in the locations of 84 landslides are analysed during two rainfall episodes, which represent the most common precipitation patterns: October–November 2008 and June 2010. Empirical data allowed the definition of available water capacity percentages of 99–100% as critical soil moisture conditions for the landslide triggering. Intensity-duration rainfall thresholds were calculated for each episode, considering the periods with sustained high soil moisture levels before the occurrence of each analysed landslide event. For this purpose, data from daily water balance models and weather stations were used. An inverse relationship between the duration of the precipitation and its intensity, consistent with published intensity-duration thresholds, was observed, showing relevant seasonal differences. 相似文献
287.
B. Matasci G. M. Stock M. Jaboyedoff D. Carrea B. D. Collins A. Guérin G. Matasci L. Ravanel 《Landslides》2018,15(5):859-878
Rockfalls strongly influence the evolution of steep rocky landscapes and represent a significant hazard in mountainous areas. Defining the most probable future rockfall source areas is of primary importance for both geomorphological investigations and hazard assessment. Thus, a need exists to understand which areas of a steep cliff are more likely to be affected by a rockfall. An important analytical gap exists between regional rockfall susceptibility studies and block-specific geomechanical calculations. Here we present methods for quantifying rockfall susceptibility at the cliff scale, which is suitable for sub-regional hazard assessment (hundreds to thousands of square meters). Our methods use three-dimensional point clouds acquired by terrestrial laser scanning to quantify the fracture patterns and compute failure mechanisms for planar, wedge, and toppling failures on vertical and overhanging rock walls. As a part of this work, we developed a rockfall susceptibility index for each type of failure mechanism according to the interaction between the discontinuities and the local cliff orientation. The susceptibility for slope parallel exfoliation-type failures, which are generally hard to identify, is partly captured by planar and toppling susceptibility indexes. We tested the methods for detecting the most susceptible rockfall source areas on two famously steep landscapes, Yosemite Valley (California, USA) and the Drus in the Mont-Blanc massif (France). Our rockfall susceptibility models show good correspondence with active rockfall sources. The methods offer new tools for investigating rockfall hazard and improving our understanding of rockfall processes. 相似文献
288.
Reza Deevsalar Ryuichi Shinjo Jean P. Liégeois Mohammad V. Valizadeh Jamshid Ahmadian Hadi Yeganehfar Mamoru Murata Iain Neill 《Swiss Journal of Geoscience》2018,111(1-2):269-293
The Malayer–Boroujerd plutonic complex (MBPC) in western Iran, consists of a portion of a magmatic arc built by the northeast verging subduction of the Neo-Tethys plate beneath the Central Iranian Microcontinent (CIMC). Middle Jurassic-aged felsic magmatic activity in MBPC is manifested by I-type and S-type granites. The mafic rocks include gabbroic intrusions and dykes and intermediate rocks are dioritic dykes and minor intrusions, as well as mafic microgranular enclaves (MMEs). MBPC Jurassic-aged rocks exhibit arc-like geochemical signatures, as they are LILE- and LREE-enriched and HFSE- and HREE-depleted and display negative Nb–Ta anomalies. The gabbro dykes and intrusions originated from metasomatically enriched garnet-spinel lherzolite [Degree of melting (fmel) ~ 15%] and exhibit negative Nd and positive to slightly negative εHf(T) (+ 3.0 to ? 1.6). The data reveal that evolution of Middle Jurassic magmatism occurred in two stages: (1) deep mantle-crust interplay zone and (2) the shallow level upper crustal magma chamber. The geochemical and isotopic data, as well as trace element modeling, indicate the parent magma for the MBPC S-type granites are products of upper crustal greywacke (fmel: 0.2), while I-type granites formed by partial melting of amphibolitic lower crust (fmel: 0.25) and mixing with upper crustal greywacke melt in a shallow level magma chamber [Degree of mixing (fmix): 0.3]. Mixing between andesitic melt leaving behind a refractory dense cumulates during partial crystallization of mantle-derived magma and lower crustal partial melt most likely produced MMEs (fmix: 0.2). However, enriched and moderately variable εNd(T) (? 3.21 to ? 4.33) and high (87Sr/86Sr)i (0.7085–0.7092) in dioritic intrusions indicate that these magmas are likely experienced assimilation of upper crustal materials. The interpretations of magmatic activity in the MBPC is consistent with the role considered for mantle-derived magma as heat and mass supplier for initiation and evolution of magmatism in continental arc setting, elsewhere. 相似文献
289.
Zsuzsanna Szabó Nóra Edit Gál Éva Kun Teodóra Szőcs György Falus 《Environmental Earth Sciences》2018,77(12):460
CO2 geological storage is a transitional technology for the mitigation of climate change. In the vicinity of potential CO2 reservoirs in Hungary, protected freshwater aquifers used for drinking water supplies exist. Effects of disaster events of CO2 escape and brine displacement to one of these aquifers have been studied by kinetic 1D reactive transport modelling in PHREEQC. Besides verifying that ion concentrations in the freshwater may increase up to drinking water limit values in both scenarios (CO2 or brine leakage), total porosity of the rock is estimated. Pore volume is expected to increase at the entry point of CO2 and to decrease at further distances, whereas it shows minor increase along the flow path for the effect of brine inflow. Additionally, electrical conductivity of water is estimated and suggested to be the best parameter to measure for cost-effective monitoring of both worst-case leakage scenarios. 相似文献
290.
Assessment of the acid drainage neutralization capacity and the toxic metals lixiviation of tailing from Guanajuato mining district,Mexico 总被引:1,自引:0,他引:1
María Elena García-Arreola Luisa María Flores-Vélez Marcos Loredo-Tovías Alfredo Aguillón-Robles Rubén Alfonso López-Doncel Irene Cano-Rodríguez Sonia Hortensia Soriano-Pérez 《Environmental Earth Sciences》2018,77(9):355
In Mexico, many environmental problems are generated by large mining activities taking place in several mining districts. These mining activities produce great quantities of residues; large majorities of these have high sulfur content, which could generate acid drainage due to their interaction with the oxygen in the environment. The study area was located in the Mining District of Guanajuato, Mexico with abandoned tailings generated mainly by the gold and silver production. Two areas, called as Monte de San Nicolás (SN) and Peregrina (P) were selected for this study. The results study shows that there was no risk of production of acid drainage, since these tailings contained high amount of carbonates, which neutralized the generation of acidity and consequently decreased the possibility of leaching of some elements. However, not all elements leach in acid pH, as arsenic bound to oxyhydroxides, which is in a basic environment and its increased release by increasing the pH. 相似文献