A field extruder for rapidly sectioning near-surface cores from lakes and wetlands     

Paul H. Glaser  Mark Griffith 《Journal of Paleolimnology》2007,38(3):459-466

The soft uppermost sediments in lakes and wetlands contain important records of past environmental change. Although the technology for coring these sediments is relatively well established, there has been a continuing effort to improve the design of equipment that can provide the precise volumetric samples required for high-resolution dating and elemental analysis. Soft-sediment cores are usually sectioned near a coring site under a wide range of field conditions creating a challenge for both field crews and equipment. A new field extruder was therefore designed to simplify the process of fine-sectioning these cores in the field while improving volumetric-sampling accuracy. The new extruder is relatively light, stable, and easy to use, but sufficiently strong to extrude long continuous cores of stiff sediment if required. The key features of this extruder minimize sampling errors by enabling an operator to automate the measurement and extrusion of a pre-determined volume of sediment. The extruder was successfully field tested on a variety of sediment types in a large wetland from southern Florida, USA and proved easy to master by even inexperienced field crews.  相似文献   

The present state and future strategies of Unesco's man and the biosphere (MAB) programme (The example of the MAB field projects in the European Alps)     

G. Glaser 《GeoJournal》1978,2(5):488-491

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Surface sediment carbonate mineralogy and water column chemistry: Nicaragua Rise versus the Bahamas     

AndrW. Droxler  John W. Morse  Karen S. Glaser  Geoffrey A. Haddad  Paul A. Baker 《Marine Geology》1991,100(1-4):277-289

Periplatform surface sediments were studied for carbonate mineralogy in conjunction with analyses of the water column for carbonate chemistry on the eastern Northern Nicaragua Rise (NNR) in the Caribbean Sea. The results show a strong correspondence between variations and disappearance, with increasing water depth, of metastable carbonate minerals (fine aragonite and magnesian calcite) and their respective saturation levels in the overlying waters. Similar correspondence between variations in sediment proportions of fine aragonite and magnesian calcite and their respective saturation levels has previously been established in the Bahamas. There are, however, significant differences between the two areas. The sharp decrease in aragonite content and the measured aragonite saturation level occur at 4000 m in the Bahamas, compared to 1800 m on the eastern NNR. In both areas, magnesian calcite minima correspond to the in situ PCO₂ maxima in the water column. The magnesian calcite minimum, however, is at 950 m in the Bahamas and 750 m on the eastern NNR. Magnesian calcite disappears in the Bahamas at 3800 m and at 2000 m on the eastern NNR. These results demonstrate the importance of the influence of overlying water chemistry on the preservation of metastable carbonate minerals in off-bank periplatform sediments, and they clearly demonstrate the difference in terms of carbonate preservation between the poorly ventilated waters of the Caribbean Sea and the well-oxygenated waters of the adjacent Atlantic Ocean. They also open the possibility of obtaining paleoceanographic information on the depth of the CO₂ maximum (O₂ minimum) and its separation from the aragonite saturation depth in at least some areas.  相似文献   

Influence of rock mass strength on the erosion rate of alpine cliffs   总被引：1，自引：0，他引：1  

Jeffrey R. Moore  Johnny W. Sanders  William E. Dietrich  Steven D. Glaser 《地球表面变化过程与地形》2009,34(10):1339-1352

Collapse of cliff faces by rockfall is a primary mode of bedrock erosion in alpine environments and exerts a first‐order control on the morphologic development of these landscapes. In this work we investigate the influence of rock mass strength on the retreat rate of alpine cliffs. To quantify rockwall competence we employed the Slope Mass Rating (SMR) geomechanical strength index, a metric that combines numerous factors contributing to the strength of a rock mass. The magnitude of cliff retreat was calculated by estimating the volume of talus at the toe of each rockwall and projecting that material back on to the cliff face, while accounting for the loss of production area as talus buries the base of the wall. Selecting sites within basins swept clean by advancing Last Glacial Maximum (LGM) glaciers allowed us to estimate the time period over which talus accumulation occurred (i.e. the production time). Dividing the magnitude of normal cliff retreat by the production time, we calculated recession rates for each site. Our study area included a portion of the Sierra Nevada between Yosemite National Park and Lake Tahoe. Rockwall recession rates determined for 40 alpine cliffs in this region range from 0·02 to 1·22 mm/year, with an average value of 0·28 mm/year. We found good correlation between rockwall recession rate and SMR which is best characterized by an exponential decrease in erosion rate with increasing rock mass strength. Analysis of the individual components of the SMR reveals that joint orientation (with respect to the cliff face) is the most important parameter affecting the rockwall erosion rate. The complete SMR score, however, best synthesizes the lithologic variables that contribute to the strength and erodibility of these rock slopes. Our data reveal no strong independent correlations between rockwall retreat rate and topographic attributes such as elevation, aspect, or slope angle. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Guest Editorial     

Christian Pfister  Rudolf Brázdil  Rüdiger Glaser 《Climatic change》1999,43(1):3-4

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Whose sustainability? Top–down participation and emergent rules in marine protected area management in Indonesia     

Marion Glaser  Wasistini Baitoningsih  Sebastian C.A. Ferse  Muhammad Neil  Rio Deswandi 《Marine Policy》2010

A review of a major community-based marine protected area programme (CB-MPA) in an Indonesian island archipelago is the point of departure for this article. Despite a well-designed institutional structure to facilitate local participation, local knowledge about the CB-MPA is found to be low and resource access and influence on decision-making in the programme is negligible for the majority of islanders. At the same time, most of those who know about the programme consider it as pertaining to the public authority only. These findings stand in contrast to evidence on non-formal ways of protecting and managing marine areas in the same geographical area but outside the formal MPA institutional framework. In particular, the article identifies a number of emergent rules-in-use in marine management, which operate parallel to legally established MPAs. It is argued that emergent forms of marine area protection such as non-formal self-organising island exclusion zones (IEZ) offer as yet mostly unused potentials for formal MPA development, particularly in those coastal and marine areas without traditional forms of marine and coastal management.  相似文献   

The dynamic balance between organic acids and circumneutral groundwater in a large boreal peat basin     

D.I. Siegel  P.H. Glaser  J. So  D.R. Janecky 《Journal of Hydrology》2006,320(3-4):421-431

Large raised bogs and patterned fens cover 56% of the landscape in the Glacial Lake Agassiz region of northern Minnesota (USA). Organic acids supply most of the acidity in the surface water of the bogs, but groundwater upwelling from the underlying glacial deposits neutralizes these organic acids within deep peat. Substantial concentrations of organic acids also occur in the surface waters of fens mixed with variable amounts of inorganic solutes contributed by groundwater discharge. We used a triprotic analog model to determine the extent to which organic acids in fen and bog waters behave as strong or weak acids. The modeling approach optimized charge balance by calibrating estimates of mole site density in the DOC (dissolved organic carbon) of surface and pore waters with estimates of triprotic acid dissociation constants. Before the calibration process, all of the bog waters and 76% of the fen waters had more than +20% imbalance in charge balance. After calibration, more than 75% of all waters were electrochemically balanced within 20%. In the best calibration, the mole site denisty of bog DOC was estimated as 0.05 mmol/mmol C., approximately six times smaller than that estimated for fen DOC or the DOC in the fen deeper fen peats that underlie all bog landforms. The three modeled de-protonation constants were; pK_a1=3.0, pK_a2=4.5 and pK_a3=7.0 for the bog DOC, and; pK_a1=5.2, pK_a2= 6.5 and pK_a3=7.0 for the fen DOC. Bog DOC, behaves as a strong acid despite its small mole site density. The DOC in bog runoff can therefore theoretically acidify the surface waters in adjacent fens wherever these waters do not receive sufficient buffering alkalinity from active groundwater seepage.  相似文献   

Ozone and PAN Formation Inside and Outside of the Berlin Plume – Process Analysis and Numerical Process Simulation     

U. Corsmeier  N. Kalthoff  B. Vogel  M.-U. Hammer  F. Fiedler  Ch. Kottmeier  A. Volz-Thomas  S. Konrad  K. Glaser  B. Neininger  M. Lehning  W. Jaeschke  M. Memmesheimer  B. Rappenglück  G. Jakobi 《Journal of Atmospheric Chemistry》2002,42(1):289-321

During the BERLIOZ field phase on 20 July 1998 a 40 km wide ozone-plume 30 to 70 km north of Berlin in the lee of the city was detected. The ozone mixing ratio inside the plume was app. 15 ppb higher than outside, mainly caused by high ozone precursor emissions in Berlin, resulting in a net chemical ozone production of 6.5 ppb h^–1, which overcompensates ozone advection of –3.6 ppb h^–1 andturbulent diffusion of –1.1 ppb h^–1. That means, although moreozone leaves the control volume far in the lee of Berlin than enters it at the leeside cityborder and although turbulent diffusion causes a loss of ozone in the leeside control volume the chemical production inside the volume leads to a net ozone increase. Using a semi-Lagrangian mass budget method to estimate the net ozone production, 5.0 ppb h^–1 are calculated for theplume. This means a fraction of about 20% of ozone in the plume is producedby local emissions, therefore called `home made' by the Berlin emissions. For the same area KAMM/DRAIS simulations using an observation based initialisation, results in a net production rate between 4.0 and 6.5 ppbh^–1, while the threefold nested EURAD model gives 6.0 ppbh^–1. The process analysis indicates in many cases goodagreement (10% or better) between measurements and simulations not only in the ozone concentrations but also with respect to the physical and chemical processes governing the total change. Remaining differences are caused by different resolution in time and space of the models and measurements as well as by errors in the emission calculation.The upwind-downwind differences in PAN concentrations are partly similar to those of ozone, because in the BERLIOZ case they are governed mainly by photochemical production. While in the stable boundary layer at night and windward of Berlin 0.1 to 0.3 ppb are detected, in the centre of the plume at noon concentrations between 0.75 ppb and 1.0 ppb are measured. The O₃/PAN ratio is about 80 to 120 and thus due to the relatively lowPAN concentrations significantly higher than found in previous studies. The low PAN formation on 20 July, was mainly restricted by the moderate nonmethane hydrocarbon levels, whereas high PAN concentrations of 3.0 ppb on 21 July, are caused by local production in the boundary layer and by large scale advection aloft.  相似文献   

Flood Events of Selected European Rivers in the Sixteenth Century     

Rudolf Brázdil  Rüdiger Glaser  Christian Pfister  Petr Dobrovolný  Jean-Marc Antoine  Mariano Barriendos  Dario Camuffo  Mathias Deutsch  Silvia Enzi  Emanuela Guidoboni  Oldřich Kotyza  Fernando Sanchez Rodrigo 《Climatic change》1999,43(1):239-285

The severity and frequency of sixteenth-century floods of the Rhine, the Main, the middle and upper Elbe with its tributaries, rivers of northern and central Italy, the Garonne and rivers in Catalonia and Andalusia are analyzed using documentary evidence. The basic topographical and hydrological characteristics of the rivers investigated as well as the synoptic causes of their flooding during the instrumental period are presented. Different examples of modifications of the run-off process due to anthropogenic activity are discussed. Prevalence in flood occurrence during the second half of the sixteenth century in comparison to the first half is typical for central European and Andalusian rivers (mainly in the 1560s and 1590s) and agrees with the evolution of precipitation patterns. On the other hand, Italian and Catalonian rivers, in part, had a higher occurrence of floods during the first half of the century. Changes in the flooding seasons in both halves of the century are not unambiguous. Results of an analysis on a broader European scale show floods to be a random natural phenomena with limited areal extent defined by the spatial influence of forcing meteorological factors (continuous heavy rains, sudden melting of thick snow cover, etc.). Despite some limitations of documentary evidence, series of reconstructed historical floods are valuable sources of proxy data which can be utilized for the study of the flooding fluctuations in the pre-instrumental period.  相似文献   

Tracking rapidly changing dynamical systems using a non‐parametric statistical method based on wavelets     

Jianye Ching  Steven D. Glaser 《地震工程与结构动力学》2003,32(15):2377-2406

A non‐parametric statistical method of tracking rapidly changing dynamical systems is introduced. The method implements the non‐linear wavelet thresholding estimator to estimate the evolutionary transfer function of the system. The consistency and optimality of the resulting estimate of our method on rapidly changing systems are stated, while no linear estimator can achieve the same optimality. Two examples of real data are studied using this non‐parametric method, including two vertical seismic array case studies and a series of seismic slope experiments. The analysis results are consistent with previous research for the vertical seismic array data. Moreover, our estimate is superior to those from previous research in the sense that our estimate is neither over‐smoothed nor under‐smoothed. The ana‐ lysis results are also consistent with the experimental observations for the seismic slope experimental data. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献