Opaline and Al–Si phytoliths from a tropical mire system of West Malaysia: abundance, habit, elemental composition, preservation and significance     

Raphael A. J. Wüst  R. Marc Bustin 《Chemical Geology》2003,200(3-4):267-292

Abundant and unique opaline and Al–Si phytoliths and opaline bioliths have been discovered in Holocene peat deposits of tropical Tasek Bera in Peninsular Malaysia. These are secreted mainly by plants (higher plants and algae) and incorporated in the sediment cycle during the rapid biomass turnover. Many wetland plants have entire skeletons secreted. The study shows that differing plant parts of same species as well as same parts of differing plant species incorporate different amounts of elements. Whilst deciduous trees of the swamp forest have phytoliths enriched in Al, most phytoliths of palms, sedges and grasses of the littoral swamp are composed of opaline silica. Incorporation of Al and many other elements into relatively stable phytoliths is the result of high evapotranspiration rate and ample plant-available elements and can serve to detoxify the soil solution. Because of the abundance of such opaline and Al–Si structures, spongillid and algal remains in acid peat-accumulating environments, tropical peatlands represent repositories of Si and Al, which together with variable amounts of other elements could provide the prime material for silicate neoformation during later diagenetic processes. Neoformation of minerals from bioliths would explain the scarcity of biogenic remains in Carboniferous and Tertiary coal deposits. Furthermore, incorporation of major elements in phytoliths may limit the rate of leaching of these elements in an environment where biomass turnover is rapid, thus reducing the loss of nutrients and other plant-essential elements. Most nutrients of tropical peats are recycled by plants within the top 150 cm and an upward migration of plant-essential elements, such as Mg, Ca, or P, but also of Si and Al, occurs during peat accumulation. Such elemental cycling strongly influences the geochemical composition of the peats during mire evolution. Utilizing Al for normalization of major and minor elements of tropical peats for paleoclimatic and paleodepositional analyses may thus result in incorrect interpretations.  相似文献   

Structural-permeability favorability in crystalline rocks and implications for groundwater flow paths: a case study from the Aar Massif (central Switzerland)     

Raphael Schneeberger  Daniel Egli  Georg W. Lanyon  Urs K. Mäder  Alfons Berger  Florian Kober  Marco Herwegh 《Hydrogeology Journal》2018,26(8):2725-2738

Groundwater flow in granitic bedrock is of major interest for underground projects such as radioactive waste disposal. It is generally accepted that granitic rocks of the upper crust are characterized as faulted low-porosity rocks showing fault-related permeability. In this study, the influence of existing faults on the present-day water flow in the Grimsel Test Site (Switzerland), an underground rock laboratory situated in granitoid rocks, was investigated by mapping water discharges. As a result, the link between water flow and faults considering slip-tendency analysis and fault intersections is evaluated. Water-conducting features were combined in a structural-permeability favorability map. Faults and dykes occur as three orientation groups, NE–SW, E–W, and NW–SE trending, all steeply dipping southwards with fault intersections also steeply plunging southwards. In total, 100 water discharges were mapped in summer 2014 and 85 in winter 2016, which are located along faults or fault intersections. A comparison of water discharges with structures showed that high-slip-tendency metabasic dykes and fault or dyke intersections represent the dominant flow paths. Further, it could be demonstrated that higher slip-tendency tends to lead to enhanced average hydraulic conductivity and therefore more constant water flow. Based on water fluxes, fault intersections are inferred to represent first-order locations of water percolation followed by high-slip-tendency metabasic dykes. The combination of all water-conducting features into a structural-permeability map results in covering all water discharges. Therefore, the structural-permeability favorability map can serve as suitable representation for constraining water inflow in fractured granitoid host rocks.  相似文献   

Ocean urea fertilization for carbon credits poses high ecological risks     

Glibert PM  Azanza R  Burford M  Furuya K  Abal E  Al-Azri A  Al-Yamani F  Andersen P  Anderson DM  Beardall J  Berg GM  Brand L  Bronk D  Brookes J  Burkholder JM  Cembella A  Cochlan WP  Collier JL  Collos Y  Diaz R  Doblin M  Drennen T  Dyhrman S  Fukuyo Y  Furnas M  Galloway J  Granéli E  Ha DV  Hallegraeff G  Harrison J  Harrison PJ  Heil CA  Heimann K  Howarth R  Jauzein C  Kana AA  Kana TM  Kim H  Kudela R  Legrand C  Mallin M  Mulholland M  Murray S  O'Neil J  Pitcher G  Qi Y  Rabalais N  Raine R  Seitzinger S  Salomon PS  Solomon C 《Marine pollution bulletin》2008,56(6):1049-1056

The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.  相似文献   

Optimizing Wellfield Operation in a Variable Power Price Regime          下载免费PDF全文

Peter Bauer‐Gottwein  Raphael Schneider  Claus Davidsen 《Ground water》2016,54(1):92-103

Wellfield management is a multiobjective optimization problem. One important objective has been energy efficiency in terms of minimizing the energy footprint (EFP) of delivered water (MWh/m³). However, power systems in most countries are moving in the direction of deregulated markets and price variability is increasing in many markets because of increased penetration of intermittent renewable power sources. In this context the relevant management objective becomes minimizing the cost of electric energy used for pumping and distribution of groundwater from wells rather than minimizing energy use itself. We estimated EFP of pumped water as a function of wellfield pumping rate (EFP‐Q relationship) for a wellfield in Denmark using a coupled well and pipe network model. This EFP‐Q relationship was subsequently used in a Stochastic Dynamic Programming (SDP) framework to minimize total cost of operating the combined wellfield‐storage‐demand system over the course of a 2‐year planning period based on a time series of observed price on the Danish power market and a deterministic, time‐varying hourly water demand. In the SDP setup, hourly pumping rates are the decision variables. Constraints include storage capacity and hourly water demand fulfilment. The SDP was solved for a baseline situation and for five scenario runs representing different EFP‐Q relationships and different maximum wellfield pumping rates. Savings were quantified as differences in total cost between the scenario and a constant‐rate pumping benchmark. Minor savings up to 10% were found in the baseline scenario, while the scenario with constant EFP and unlimited pumping rate resulted in savings up to 40%. Key factors determining potential cost savings obtained by flexible wellfield operation under a variable power price regime are the shape of the EFP‐Q relationship, the maximum feasible pumping rate and the capacity of available storage facilities.  相似文献   

Comment on “Complex Inversion of MRT Signals under Different Loop Configurations for Groundwater Exploration” by Bin Chen,Xiangyun Hu,Jianhui Li,Yajun Liu, 2016, v. 55, no. 2: 171‐182          下载免费PDF全文

Mike Müller‐Petke  Chuandong Jiang  Thomas Günther  Raphael Dlugosch 《Ground water》2017,55(3):289-290

  相似文献   

Trophic relationships in tidepool fish assemblages of the tropical Southwestern Atlantic          下载免费PDF全文

Caio R. Pimentel  Lucy S. H. Soares  Raphael M. Macieira  Jean‐Christophe Joyeux 《Marine Ecology》2018,39(2)

Trophic studies are fundamental to understanding the dynamics of assemblages and functional roles of species within ecosystems, contributing to the identification of factors responsible for the organization and structure of communities. This study aimed to analyse the trophic organization of tidepool fish assemblages in the tropical Southwestern Atlantic, based on the underlying idea that food resources are not limiting and that trophic guild formation is not driven by food competition. Diets were based on feeding index values of food categories for 12 representative species collected in six tidepools (20º49′ S, 40º36′ W) at quarterly intervals (2005 to 2007). The main food categories were small crustaceans, polychaetes and macroalgae. Multivariate techniques evidenced two multispecific trophic guilds: small‐prey carnivores, including Bathygobius soporator, Bathygobius geminatus, Malacoctenus delalandii and Halichoeres poeyi, and herbivores, including Sparisoma axillare and Acanthurus bahianus. Other species presented significantly different diets and were classified into the following guilds: omnivores feeding on filamentous algae and copepods (Abudefduf saxatilis); large‐prey carnivores (Labrisomus nuchipinnis); omnivores feeding on polychaetes and filamentous algae (Stegastes fuscus); and polychaete feeders (Ahlia egmontis). Gymnothorax funebris and Gymnothorax moringa were classified as carcinophagores and piscivores, respectively. Trophic organization appears related to species convergence toward the use of abundant food resources, driven by a combination of factors allowing some resource partitioning through inter‐specific differences in consumer size, microhabitat, behavior, and trophic specialization.  相似文献   

Deformation-induced cordierite breakdown–An example from western Maine,USA     

Ioan V. Sanislav  Ahmed S. A. A. Abu Sharib  Raphael S. A. Quentin de Gromard 《Journal of Metamorphic Geology》2020,38(8):831-852

Preservation of partially completed metamorphic reactions in the form of partial pseudomorphs is very important as it provides direct insight onto the reaction mechanism and the phases involved in the reaction. The staurolite and andalusite grade rocks in western Maine, USA, contain cordierite porphyroblasts partly pseudomorphed by coarse-grained muscovite and biotite. The pseudomorphs consist of a cordierite core surrounded by a reaction rim. Modal mineralogy, calculated using the ImageJ processing software based on backscatter images and X-ray compositional maps, reveals that the core consists of cordierite (53.5%), muscovite (22.8%), biotite (9.1%), quartz (1 0.4%), plagioclase (3.1%) and ilmenite/pyrrhotite and apatite (1.1%) whereas the reaction rim consists of cordierite (1.8%), muscovite (51.6%), biotite (30.4%), quartz (4.3%), plagioclase (10%), garnet (1.2%), ilmenite/pyrrhotite and apatite (0.8%). The net effect of the cordierite breakdown reaction is an increase of 226% in muscovite, 334% in biotite and 323% in plagioclase content and a decrease of 97% in cordierite. The reaction involved exchange of components with the matrix requiring addition of H₂O, K⁺, Na⁺ and Ti⁴⁺ and removal of SiO₂, Mg²⁺ and PO₄^3- from the reaction site. PT estimates using the garnet–biotite, Ti-in-biotite, Na-in-cordierite thermometers and the garnet–biotite–muscovite–plagioclase barometer indicate that cordierite breakdown occurred at ~550°C and 3.5 kbar. thermocalc modelling using the bulk rock composition suggests that cordierite is not stable at these conditions, whereas modelling using a thin section-derived bulk composition indicates that cordierite stability extends to higher pressures, and most likely that the cordierite breakdown was not PT dependent. The incorporation of Na (up to 0.18 a.f.u.) into the cordierite structure has the effect of stabilizing the cordierite under a variety of H₂O activity and limiting the role of fluids into destabilizing it. The cordierite cores contain evidence of plastic and brittle deformation in the form of subgrains and microcracks, which facilitated the infiltration of fluids that destabilized cordierite at constant PT conditions by leaching Na and introducing K. New mica growth along these structural heterogeneities suggests that deformation played an important role promoting breakdown of cordierite to muscovite and biotite.  相似文献   

Physical-Ecological Response of the California Current System to ENSO events in ROMS-NEMURO     

Cordero-Quirós  Nathalí  Miller  Arthur J.  Pan  Yunchun  Balitaan  Lawrence  Curchitser  Enrique  Dussin  Raphael 《Ocean Dynamics》2022,72(1):21-36

Ocean Dynamics - We analyze the bottom-up El Niño/Southern Oscillation (ENSO) driven physical-biological response of the California Current System (CCS) in a high-resolution,...  相似文献   

Municipal GIS and the enterprise data model     

Raphael Sussman 《International journal of geographical information science》2013,27(4):367-377

Abstract

The City of Scarborough, like many corporations, recently re-evaluated its information technology requirements. The decision was made to model the City's needs in terms of activities and data requirements, concentrating on the Municipal Data Model. First, a two year study was undertaken to understand the business activities of all the disparate components that make up the corporation. This study resulted in individual Information Resource Plans (IRP) for each department. A third year was spent in reconciling the many separate documents and creating a high-level Conceptual Data Model for a Corporate Information System. Of the thirteen broad data groupings, four were assigned to the GIS Group for the design of Detailed Data Models and to populate the resultant databases. The GIS Group, in fact, were to initiate the new Information System for the entire City. The modelling sessions involved hundreds of users from the entire user community in small and large groups, in intensive entity-definition activities, in technical review sessions and in the general examination of context. The detailed models were validated by involving still more users and by testing the model in prototypes, special projects and joint ventures. The GIS Project has demonstrated that data modelling is an effective and realistic method of reflecting the municipality as an enterprise.  相似文献   

Seasonal rainfall variability in southeast Africa during the nineteenth century reconstructed from documentary sources     

David J. Nash  Kathleen Pribyl  Jørgen Klein  Raphael Neukom  Georgina H. Endfield  George C. D. Adamson  Dominic R. Kniveton 《Climatic change》2016,134(4):605-619

  相似文献