Diatomeenstratigraphische Untersuchungen zur Trophieänderung und Industrieschlammakkumulation im Traunsee/Österreich     

Roland Schmidt 《Aquatic Sciences - Research Across Boundaries》1989,51(4):317-337

Three cores from Traunsee were investigated and compared with respect to diatom stratigraphy concerning dating of incursions into and rate of accumulation of industrial tailings in the profundal zone.

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Comparative study of the kinetics and mechanisms of dissolution of carbonate minerals   总被引：9，自引：0，他引：9  

Lei Chou  Robert M. Garrels  Roland Wollast 《Chemical Geology》1989,78(3-4):269-282

The influence of pH on the rate of dissolution of various carbonates (calcite, aragonite, witherite, magnesite and dolomite) has been investigated at 25°C using a continuous fluidized bed reactor. The general rate dependence on pH observed for the simple carbonates is very similar and is in agreement with the results observed for calcite and aragonite by L.N. Plummer and coworkers. However, the rate of dissolution of magnesite is approximately four orders of magnitude lower than calcite.

For simple carbonates, the elementary steps involved in the dissolution reaction are:

where M represents the metal ion which can be Ca, Mg and Ba. According to the stoichiometry of the three reaction steps and the thermodynamic constraints, the total forward and backward rates can be expressed as:

The rate constants (k₁, k₂, k₃ and k₋₃) determined with our experimental results for calcite, aragonite and witherite show that the dissolution rates are similar for these three minerals and that the nature of the cations does not play a significant role. The good agreement between the K_sp calculated from the measured k₃/k₋₃ ratio and the theromodynamic value suggests that our dissolution mechanism is coherent.

The rate dependence on pH of the dissolution of dolomite obeys a fractional order at low pH's and confirms previously published observations therein. However, the two-step reaction mechanism proposed does not explain the fractional reaction order observed, which is likely due to a more complex surface reaction.  相似文献   

Chemistry of high mountain lakes in siliceous chatchments of the Central Eastern Alps     

Roland Psenner 《Aquatic Sciences - Research Across Boundaries》1989,51(2):108-128

Alpine lakes in siliceous catchments of Tyrol and Carinthia (Austria) show signs of acidification. About 9% of the studied lakes have no alkalinity, more than 20% are below pH 6. About two thirds of all lakes have acid neutralizing capacities below 100 eq 1^–1. In spite of moderate precipitation acidity, some lakes show considerable concentrations of dissolved reactive aluminum during or shortly after snowmelt. High altitude lakes of the Alps are definitely more acidic than high mountain lakes in remote areas. Large differences in water and soil chemistry of nearby situated lakes were attributed to heterogeneities of bedrock geology. Paleolimnological investigations on former pH values of five lakes, based on diatom assemblages in the sediment, showed different developments: recent and past acidification, stable conditions, and alkalinization.  相似文献   

Experience from preparation and application of till/bentonite mixtures     

Roland Pusch  Gsta Alstermark 《Engineering Geology》1985,21(3-4):377-382

Clay-based layers which serve to minimize infiltration of surface water into waste piles seem to form a promising concept, since their hydraulic conductivity can be kept so low that the net effect of cyclic drying and wetting in Sweden will be that no water penetrates. Problems may arise, however, from physico/chemical processes as well as from swelling, one example being given in this paper.  相似文献   

Diatoms as indicators of climatic and limnological change in Swedish Lapland: a 100-lake calibration set and its validation for paleoecological reconstructions   总被引：2，自引：0，他引：2  

Christian Bigler  Roland I. Hall 《Journal of Paleolimnology》2002,27(1):97-115

This study investigated the distribution of subfossil diatom assemblages in surficial sediments of 100 lakes along steep ecological and climatic gradients in northernmost Sweden (Abisko region, 67.07° N to 68.48° N latitude, 17.67° E to 23.52° E longitude) to develop and cross-validate transfer functions for paleoenvironmental reconstruction. Of 19 environmental variables determined for each site, 15 were included in the statistical analysis. Lake-water pH (8.0%), sedimentary loss-on-ignition (LOI, 5.9% and estimated mean July air temperature (July T, 4.8%) explained the greatest amounts of variation in the distribution of diatom taxa among the 100 lakes. Temperature and pH optima and tolerances were calculated for abundant taxa. Transfer functions, based on WA-PLS (weighted averaging partial least squares), were developed for pH (r² = 0.77, root-mean-square-error of prediction (RMSEP) = 0.19 pH units, maximum bias = 0.31, as assessed by leave-one-out cross-validation) based on 99 lakes and for July T (r² = 0.75, RMSEP = 0.96 °C, max. bias = 1.37 °C) based on the full 100 lake set. We subsequently assessed the ability of the diatom transfer functions to estimate lake-water pH and July T using a form of independent cross-validation. To do this, the 100-lake set was divided in two subsets. An 85-lake training-set (based on single limnological measurements) was used to develop transfer functions with similar performance as those based on the full 100 lakes, and a 15-lake test-set (with 2 years of monthly limnological measurements throughout the ice-free seasons) was used to test the transfer functions developed from the 85-lake training-set. Results from the intra-set cross-validation exercise demonstrated that lake-specific prediction errors (RMSEP) for the 15-lake test-set corresponded closely with the median measured values (pH) and the estimations based on spatial interpolations of data from weather stations (July T). The prediction errors associated with diatom inferences were usually within the range of seasonal and interannual variability. Overall, our results confirm that diatoms can provide reliable and robust estimates of lake-water pH and July T, that WA-PLS is a robust calibration method and that long-term environmental data are needed for further improvement of paleolimnological transfer functions.  相似文献   

Towards an integration of process measurements, archive analysis and modelling in geomorphology — the Kärkevagge experimental site, Abisko area, northern Sweden     

Martin Gude  Gerhard Daut  Susanne Dietrich  Roland Mäusbacher  Christer Jonasson  Annett Bartsch  & Dieter Scherer 《Geografiska Annaler: Series A, Physical Geography》2002,84(3-4):205-212

The analysis of Holocene geomorphic process activity demands long–term data sets, which are available for the Kärkevagge catchment due to 50 years of intensive geomorphologic field studies. This data set is used in combination with additional field measurements, remote sensing and digital elevation model (DEM) analysis to provide input data for modelling Holocene valley development. On the basis of this information, geomorphic process units (GPUs) are defined by means of GIS modelling. These units represent areas of homogeneous process composition that transfer sediments. Since the data base enables the quantification of single processes, the interaction of processes within the units can also be quantified. Applying this concept permits calculation of recent sediment transfer rates and hence leads to a better understanding of actual geomorphic landscape development activity. To extrapolate these data in time and space the process–related sediments in the valley are analysed for depth and total volume, primarily using geophysical methods. In this fashion the validity of measured process rates is evaluated for the Holocene time scale. Results from this analysis are exemplified in a cross–profile showing some of the principal sediment units in the valley. For example, the measured modern rates on a slush torrent debris fan seem to represent the Holocene mean rate. This approach should also be suitable for revealing Holocene geomorphic landscape development in terms of climate change.  相似文献   

Non-linear body wave teleseismic tomography along the TOR array   总被引：2，自引：0，他引：2  

Z. Hossein Shomali  Roland G. Roberts  the TOR Working Group 《Geophysical Journal International》2002,148(3):562-574

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Modelling surface‐water depression storage in a Prairie Pothole Region          下载免费PDF全文

Lauren Hay  Parker Norton  Roland Viger  Steven Markstrom  R. Steven Regan  Melanie Vanderhoof 《水文研究》2018,32(4):462-479

In this study, the Precipitation‐Runoff Modelling System (PRMS) was used to simulate changes in surface‐water depression storage in the 1,126‐km² Upper Pipestem Creek basin located within the Prairie Pothole Region of North Dakota, USA. The Prairie Pothole Region is characterized by millions of small water bodies (or surface‐water depressions) that provide numerous ecosystem services and are considered an important contribution to the hydrologic cycle. The Upper Pipestem PRMS model was extracted from the U.S. Geological Survey's (USGS) National Hydrologic Model (NHM), developed to support consistent hydrologic modelling across the conterminous United States. The Geospatial Fabric database, created for the USGS NHM, contains hydrologic model parameter values derived from datasets that characterize the physical features of the entire conterminous United States for 109,951 hydrologic response units. Each hydrologic response unit in the Geospatial Fabric was parameterized using aggregated surface‐water depression area derived from the National Hydrography Dataset Plus, an integrated suite of application‐ready geospatial datasets. This paper presents a calibration strategy for the Upper Pipestem PRMS model that uses normalized lake elevation measurements to calibrate the parameters influencing simulated fractional surface‐water depression storage. Results indicate that inclusion of measurements that give an indication of the change in surface‐water depression storage in the calibration procedure resulted in accurate changes in surface‐water depression storage in the water balance. Regionalized parameterization of the USGS NHM will require a proxy for change in surface‐storage to accurately parameterize surface‐water depression storage within the USGS NHM.  相似文献   

Modelling dynamics of the estuarine turbidity maximum and local net deposition     

Hesse  Roland F.  Zorndt  Anna  Fröhle  Peter 《Ocean Dynamics》2019,69(4):489-507

Ocean Dynamics - Net deposition in estuaries is often linked to the estuarine turbidity maximum zones, in which fine, cohesive sediments accumulate due to residual transport by the estuarine...  相似文献   

An evaluation of the hysteresis in chemical concentration–discharge (C–Q) relationships from drained,intensively managed grasslands in southwest England     

Adebayo O. Eludoyin  Bruce Griffith  Robert J. Orr  Roland Bol  Timothy A. Quine  Richard E. Brazier 《水文科学杂志》2017,62(8):1243-1254

This study examined the hysteresis exhibited in concentration–discharge (C–Q) relationships in the runoff from four hydrologically separated fields (catchments) at an intensively managed grassland. The objectives were to examine C–Q relationships constructed from high-resolution time series of flow, temperature, pH, conductivity, nitrate and turbidity, and their implications for hydrological processes. High-resolution datasets from the quality assured records of the Rothamsted Research North Wyke Farm Platform in the UK were examined using a graphical method and cross-correlation statistics. The study found that storm events based C–Q hysteresis reflects the cross-correlation that is generally hidden in time series analysis of large datasets, and that although Q and water quality variables can be effectively influenced by catchment size, the C–Q relationship is less significantly influenced. The dominant C–Q relationships of the water variables in the study area reflect that saturated overland flow was prevalent during the study period in the catchments, while the CCF results indicate coupled transfer of sediments and solute in the area at lag ≥ 0.