Equilibrium Modeling of Arsenic Adsorption in a Ternary Arsenic–Iron Oxide–Natural Organic Matter System          下载免费PDF全文

Hoda Fakour  Tsair‐Fuh Lin  Shang‐Lien Lo 《洁净——土壤、空气、水》2016,44(10):1287-1295

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Multi-level parameter structure identification for two-phase porous-media flow problems using flexible representations     

Inga Berre  Martha Lien  Trond Mannseth 《Advances in water resources》2009

We consider identification of absolute permeability (hydraulic conductivity) based on time series of pressure data in sparsely distributed wells for two-phase porous-media flow. For this problem, it is impossible to recover all details of the parameter function. On the other hand, a coarser, approximate recovery may be sufficient for many applications. We propose a novel solution approach, based on reparametrization, for such approximate identification of the parameter function. We use a nonlinear, composite representation, which is detached from the computational grid, allowing for a flexible representation of the parameter function at many resolution levels. This is utilized in a sequential multi-level estimation of the parameter function, starting at a coarse resolution, which is then gradually refined. The composite representation is designed to allow for smooth as well as sharp transitions between regions of nearly constant parameter value. Moreover, it facilitates the estimation also of the structure and smoothness of the parameter function itself. As a limiting case, the chosen representation is reduced to a zonation with implicit representation of the interior boundaries that is equivalent to a level-set representation. A motivation for the selected representation and the multi-level estimation is presented in terms of an analysis of sensitivity and nonlinearity. Numerical examples demonstrate identification of coarse-scale features of reference permeability distributions with varying degree of smoothness. Comparisons show how the multi-level strategy stabilize the identification and avoid local minima of the objective function compared to a single-level strategy.  相似文献   

Paleogene evolution and demise of the proto‐Paratethys Sea in Central Asia (Tarim and Tajik basins): Role of intensified tectonic activity at ca. 41 Ma     

Mustafa Y. Kaya  Guillaume Dupont‐Nivet  Jean‐Noël Proust  Pierrick Roperch  Laurie Bougeois  Niels Meijer  Joost Frieling  Chiara Fioroni  Sevin zkan Alt&#x;ner  Ezgi Vardar  Natasha Barbolini  Marius Stoica  Jovid Aminov  Mehmut Mamtimin  Guo Zhaojie 《Basin Research》2019,31(3):461-486

The proto‐Paratethys Sea covered a vast area extending from the Mediterranean Tethys to the Tarim Basin in western China during Cretaceous and early Paleogene. Climate modelling and proxy studies suggest that Asian aridification has been governed by westerly moisture modulated by fluctuations of the proto‐Paratethys Sea. Transgressive and regressive episodes of the proto‐Paratethys Sea have been previously recognized but their timing, extent and depositional environments remain poorly constrained. This hampers understanding of their driving mechanisms (tectonic and/or eustatic) and their contribution to Asian aridification. Here, we present a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy as well as a detailed palaeoenvironmental analysis for the Paleogene proto‐Paratethys Sea incursions in the Tajik and Tarim basins. This enables us to identify the major drivers of marine fluctuations and their potential consequences on Asian aridification. A major regional restriction event, marked by the exceptionally thick (≤ 400 m) shelf evaporites is assigned a Danian‐Selandian age (ca. 63–59 Ma) in the Aertashi Formation. This is followed by the largest recorded proto‐Paratethys Sea incursion with a transgression estimated as early Thanetian (ca. 59–57 Ma) and a regression within the Ypresian (ca. 53–52 Ma), both within the Qimugen Formation. The transgression of the next incursion in the Kalatar and Wulagen formations is now constrained as early Lutetian (ca. 47–46 Ma), whereas its regression in the Bashibulake Formation is constrained as late Lutetian (ca. 41 Ma) and is associated with a drastic increase in both tectonic subsidence and basin infilling. The age of the final and least pronounced sea incursion restricted to the westernmost margin of the Tarim Basin is assigned as Bartonian–Priabonian (ca. 39.7–36.7 Ma). We interpret the long‐term westward retreat of the proto‐Paratethys Sea starting at ca. 41 Ma to be associated with far‐field tectonic effects of the Indo‐Asia collision and Pamir/Tibetan plateau uplift. Short‐term eustatic sea level transgressions are superimposed on this long‐term regression and seem coeval with the transgression events in the other northern Peri‐Tethyan sedimentary provinces for the 1st and 2nd sea incursions. However, the 3rd sea incursion is interpreted as related to tectonism. The transgressive and regressive intervals of the proto‐Paratethys Sea correlate well with the reported humid and arid phases, respectively in the Qaidam and Xining basins, thus demonstrating the role of the proto‐Paratethys Sea as an important moisture source for the Asian interior and its regression as a contributor to Asian aridification.  相似文献   

What meta-analysis can tell us about vulnerability of marine biodiversity to ocean acidification?     

S. Dupont  N. Dorey  M. Thorndyke 《Estuarine, Coastal and Shelf Science》2010

Ocean acidification has been proposed as a major threat for marine biodiversity. Hendriks et al. [Hendriks, I.E., Duarte, C.M., Alvarez, M., 2010. Vulnerability of marine biodiversity to ocean acidification: a meta-analysis. Estuarine, Coastal and Shelf Science, doi:10.1016/j.ecss.2009.11.022.] proposed an alternative view and suggested, based on a meta-analysis, that marine biota may be far more resistant to ocean acidification than hitherto believed. However, such a meta-analytical approach can mask more subtle features, for example differing sensitivities during the life-cycle of an organism. Using a similar metric on an echinoderm database, we show that key bottlenecks present in the life-cycle (e.g. larvae being more vulnerable than adults) and responsible for driving the whole species response may be hidden in a global meta-analysis. Our data illustrate that any ecological meta-analysis should be hypothesis driven, taking into account the complexity of biological systems, including all life-cycle stages and key biological processes. Available data allow us to conclude that near-future ocean acidification can/will have dramatic negative impact on some marine species, including echinoderms, with likely consequences at the ecosystem level.  相似文献   

Numerical study of baroclinic tides in Luzon Strait   总被引：6，自引：1，他引：5  

Sen Jan  Ren-Chieh Lien  Chi-Hua Ting 《Journal of Oceanography》2008,64(5):789-802

The spatial and temporal variations of baroclinic tides in the Luzon Strait (LS) are investigated using a three-dimensional tide model driven by four principal constituents, O₁, K₁, M₂ and S₂, individually or together with seasonal mean summer or winter stratifications as the initial field. Barotropic tides propagate predominantly westward from the Pacific Ocean, impinge on two prominent north-south running submarine ridges in LS, and generate strong baroclinic tides propagating into both the South China Sea (SCS) and the Pacific Ocean. Strong baroclinic tides, ∼19 GW for diurnal tides and ∼11 GW for semidiurnal tides, are excited on both the east ridge (70%) and the west ridge (30%). The barotropic to baroclinic energy conversion rate reaches 30% for diurnal tides and ∼20% for semidiurnal tides. Diurnal (O₁ and K₁) and semidiurnal (M₂) baroclinic tides have a comparable depth-integrated energy flux 10–20 kW m⁻¹ emanating from the LS into the SCS and the Pacific basin. The spring-neap averaged, meridionally integrated baroclinic tidal energy flux is ∼7 GW into the SCS and ∼6 GW into the Pacific Ocean, representing one of the strongest baroclinic tidal energy flux regimes in the World Ocean. About 18 GW of baroclinic tidal energy, ∼50% of that generated in the LS, is lost locally, which is more than five times that estimated in the vicinity of the Hawaiian ridge. The strong westward-propagating semidiurnal baroclinic tidal energy flux is likely the energy source for the large-amplitude nonlinear internal waves found in the SCS. The baroclinic tidal energy generation, energy fluxes, and energy dissipation rates in the spring tide are about five times those in the neap tide; while there is no significant seasonal variation of energetics, but the propagation speed of baroclinic tide is about 10% faster in summer than in winter. Within the LS, the average turbulence kinetic energy dissipation rate is O(10⁻⁷) W kg^{− 1} and the turbulence diffusivity is O(10⁻³) m²s⁻¹, a factor of 100 greater than those in the typical open ocean. This strong turbulence mixing induced by the baroclinic tidal energy dissipation exists in the main path of the Kuroshio and is important in mixing the Pacific Ocean, Kuroshio, and the SCS waters.  相似文献   

Experimental and Numerical Study of Wind and Turbulence in a Near-Field Dispersion Campaign at an Inhomogeneous Site     

Xiao Wei  Eric Dupont  Eric Gilbert  Luc Musson-Genon  Bertrand Carissimo 《Boundary-Layer Meteorology》2016,160(3):475-499

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Chemical characterization of porewaters in an intertidal mudflat of the Seine estuary: relationship to erosion-deposition cycles     

Bally G  Mesnage V  Deloffre J  Clarisse O  Lafite R  Dupont JP 《Marine pollution bulletin》2004,49(3):163-173

A seasonal field study was carried out in the Seine estuary to determine the chemistry of sediment porewaters using the 'peeper' technique and changes in the elevation of the mudflats using the 'Altus' technique. This approach allowed us to evaluate the release of nutrients and to link these releases to the sediment hydrodynamics. Our results show that nutrient and organic matter cycling in a Seine estuary mudflat exhibits a seasonal behaviour, which is mainly influenced by variations in hydrodynamics. Sediments, rich organic matter, were input during floods and they were mineralized during summer and autumn, releasing nutrients and dissolved organic carbon into the sediment porewaters. The nutrient release, including ammonium, is mainly linked to the mineralization of organic matter, while the release of phosphate is delayed. The delay could be the result of phosphate association with organic matter and/or its co-precipitation with calcium and iron.  相似文献   

Southwest African climate independent of Atlantic sea surface temperatures during the Younger Dryas     

Lydie M. Dupont  Jung-Hyun Kim  Ralph R. Schneider  Ning Shi 《Quaternary Research》2004,61(3):318-324

To investigate land–sea interactions during deglaciation, we compared proxies for continental (pollen percentages and accumulation rates) and marine conditions (dinoflagellate cyst percentages and alkenone-derived sea surface temperatures). The proxies were from published data from an AMS-radiocarbon-dated sedimentary record of core GeoB 1023-5 encompassing the past 21,000 years. The site is located at ca. 2000 m water depth just north of the Walvis Ridge and in the vicinity of the Cunene River mouth. We infer that the parallelism between increasing sea surface temperatures and a southward shift of the savanna occurred only during the earliest part of the deglaciation. After the Antarctic Cold Reversal, southeast Atlantic sea surface temperatures no longer influenced the vegetation development in the Kalahari. Stronger trade winds during the Antarctic Cold Reversal and the Younger Dryas period probably caused increased upwelling off the coast of Angola. A southward shift of the Atlantic anti-cyclone could have resulted in both stronger trade winds and reduced impact of the Westerlies on the climate of southwestern Africa.  相似文献   

Seasonal ecosystem variability in remote mountain lakes: implications for detecting climatic signals in sediment records   总被引：5，自引：0，他引：5  

J. Catalan  M. Ventura  A. Brancelj  I. Granados  H. Thies  U. Nickus  A. Korhola  A.F. Lotter  A. Barbieri  E. Stuchlík  L. Lien  P. Bitušík  T. Buchaca  L. Camarero  G.H. Goudsmit  J. Kopáćek  G. Lemcke  D.M. Livingstone  B. Müller  M. Rautio  M. Šiško  S. Sorvari  F. Šporka  O. Strunecký  M. Toro 《Journal of Paleolimnology》2002,28(1):25-46

Weather variation and climate fluctuations are the main sources of ecosystem variability in remote mountain lakes. Here we describe the main patterns of seasonal variability in the ecosystems of nine lakes in Europe, and discuss the implications for recording climatic features in their sediments. Despite the diversity in latitude and size, the lakes showed a number of common features. They were ice-covered between 5–9 months, and all but one were dimictic. This particular lake was long and shallow, and wind action episodically mixed the water column throughout the ice-free period. All lakes showed characteristic oxygen depletion during the ice-covered-period, which was greater in the most productive lakes. Two types of lakes were distinguished according to the number of production peaks during the ice-free season. Lakes with longer summer stratification tended to have two productive periods: one at the onset of stratification, and the other during the autumn overturn. Lakes with shorter stratification had a single peak during the ice-free period. All lakes presented deep chlorophyll maxima during summer stratification, and subsurface chlorophyll maxima beneath the ice. Phosphorus limitation was common to all lakes, since nitrogen compounds were significantly more abundant than the requirements for the primary production observed. The major chemical components present in the lakes showed a short but extreme dilution during thawing. Certain lake features may favour the recording of particular climatic fluctuations, for instance: lakes with two distinct productive periods, climatic fluctuations in spring or autumn (e.g., through chrysophycean cysts); lakes with higher oxygen consumption, climatic factors affecting the duration of the ice-cover (e.g., through low-oxygen tolerant chironomids); lakes with higher water retention time; changes in atmospheric deposition (e.g., through carbon or pigment burial); lakes with longer stratification, air temperature changes during summer and autumn (e.g., through all epilimnetic species).  相似文献   

DESIGN OF SLIT DAMS FOR CONTROLLING STONY DEBRIS FLOWS   总被引：3，自引：0，他引：3  

Hui-Pang LIEN 《国际泥沙研究》2003,18(1)

1 INTRODUCTION Stony debris flows are natural, highly concentrated water-sediment mixture, which forms wherever the simultaneous availability of water, debris material and an adequate slope, steeper than o10 are satisfied (Gregoretti, 2000). In mountainous regions of Taiwan, due to vast development and utilization of hills, stony debris flows are important from the point of disaster prevention, since they occur frequently and often bring about heavy loss of lives and properties. Therefo…  相似文献