Book reviews     

Eckard Kleine  Hendrik M. van Aken 《Ocean Dynamics》1996,48(1):109-113

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9000 years of geochemical evolution of lithogenic major and trace elements in the sediment of an alpine lake – the role of climate, vegetation, and land-use history     

Karin A. Koinig  William Shotyk  André F. Lotter  Christian Ohlendorf  Michael Sturm 《Journal of Paleolimnology》2003,30(3):307-320

A 9000cal. year record of geochemistry was analysed in a sediment core obtained from a Swiss alpine hard-water lake (1937 ma.s.l.) that is located at the present-day tree-line. Geochemical stratigraphies are compared to changes in mineralogy, grain-size, pollen, and macrofossil records. This allows the reconstruction of the effects of changes in vegetation and of 3500 years of land-use in the catchment area on sediment geochemistry. Using principal component analysis, two major geochemical groups are distinguished: (i) Changes in concentrations of Rb, Ti, Zr, Fe, As, and Pb are closely related to corresponding changes in the concentrations of quartz and clay. They are thus considered to represent the silicate fraction which shows an increase from the oldest to the youngest core section. (ii) In contrast, Ca and Sr concentrations are positively correlated with changes in silt, sand, and calcite. They are therefore considered to represent the carbonate fraction which gradually decreased. Based on constrained cluster analysis, the core is divided into two major zones. The oldest zone (A; 9000–6400 cal.BP) is characterised by high concentrations of detrital carbonates. The more open catchment vegetation at that time promoted the physical weathering of these carbonates. The second major zone (B, 6400 cal.BP–1996 AD) is divided into four subsections with boundaries at ca. 3500, 2400, and 160cal. BP. The lower part of this zone, B1, is characterized by a gradual decrease in the carbonate-silt fraction and a pronounced increase in the silicate-clay fraction. This is concurrent with the expansion of Picea in the catchment area, which probably stabilized the soil. The middle part, B2 and B3 (3500–160cal. BP), comprises pronounced fluctuations in all elements, especially Ca, Sr, Mn, and Rb, but also in clay and silt. These changes are related to varying intensities of alpine farming. In the same section, Mn/Fe ratios are highly variable, suggesting changes in the mixing regime of the lake with phases of anoxic bottom water. The uppermost section, B4 (since 160cal. BP), is characterized by a steep decline in the silicate fraction and an increase in Ca and Sr. Despite the decrease in the silicate fraction, Pb increases, due to elevated atmospheric input resulting from early metal pollution, are masked by the high natural variability. Generally, changes in vegetation, which correspond to climate changes in the early Holocene and to human activities since ca. 3700cal. BP, are the controlling factor for variations in the geochemical composition of the sediment of Sägistalsee.  相似文献   

Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions   总被引：19，自引：0，他引：19  

Larry D. Hinzman  Neil D. Bettez  W. Robert Bolton  F. Stuart Chapin  Mark B. Dyurgerov  Chris L. Fastie  Brad Griffith  Robert D. Hollister  Allen Hope  Henry P. Huntington  Anne M. Jensen  Gensuo J. Jia  Torre Jorgenson  Douglas L. Kane  David R. Klein  Gary Kofinas  Amanda H. Lynch  Andrea H. Lloyd  A. David McGuire  Frederick E. Nelson  Walter C. Oechel  Thomas E. Osterkamp  Charles H. Racine  Vladimir E. Romanovsky  Robert S. Stone  Douglas A. Stow  Matthew Sturm  Craig E. Tweedie  George L. Vourlitis  Marilyn D. Walker  Donald A. Walker  Patrick J. Webber  Jeffrey M. Welker  Kevin S. Winker  Kenji Yoshikawa 《Climatic change》2005,72(3):251-298

The Arctic climate is changing. Permafrost is warming, hydrological processes are changing and biological and social systems are also evolving in response to these changing conditions. Knowing how the structure and function of arctic terrestrial ecosystems are responding to recent and persistent climate change is paramount to understanding the future state of the Earth system and how humans will need to adapt. Our holistic review presents a broad array of evidence that illustrates convincingly; the Arctic is undergoing a system-wide response to an altered climatic state. New extreme and seasonal surface climatic conditions are being experienced, a range of biophysical states and processes influenced by the threshold and phase change of freezing point are being altered, hydrological and biogeochemical cycles are shifting, and more regularly human sub-systems are being affected. Importantly, the patterns, magnitude and mechanisms of change have sometimes been unpredictable or difficult to isolate due to compounding factors. In almost every discipline represented, we show how the biocomplexity of the Arctic system has highlighted and challenged a paucity of integrated scientific knowledge, the lack of sustained observational and experimental time series, and the technical and logistic constraints of researching the Arctic environment. This study supports ongoing efforts to strengthen the interdisciplinarity of arctic system science and improve the coupling of large scale experimental manipulation with sustained time series observations by incorporating and integrating novel technologies, remote sensing and modeling.  相似文献   

High-resolution varve studies in Baldeggersee (Switzerland): Project overview and limnological background data     

B. Wehrli  A. F. Lotter  T. Schaller  M. Sturm 《Aquatic Sciences - Research Across Boundaries》1997,59(4):285-294

This introduction to a series of high-resolution varve studies in Baldeggersee provides both an overview of the different subprojects as well as background information on relevant limnological trends. The project was based on a new method of in-situ freezing of unconsolidated surficial sediments in deep lakes. With this freeze-core technique a detailed, high-resolution stratigraphy of the varved sediments at the deepest point of Baldeggersee has been established for the period of 1885–1993. Annual and seasonal sediment samples were analyzed. Concentrations of redox active metals in sediments were calibrated as proxy indicators for the reconstruction of hypolimnetic oxygen conditions. Particle size analysis and varve measurements were used to discriminate between the influence of nutrients and climate on sediment formation and accumulation. Baldeggersee is an ideal system for calibrating indicators of deep-water oxygen concentrations because it underwent dramatic changes in nutrient loading and redox conditions during this century. The hypolimnion has been seasonally anoxic for the last 100 years and phosphorus content decreased by a factor of five in the last 20 years. Meromixis was observed between 1960 and 1980. Since 1983 the deep water has been artificially oxygenated. This well documented change in deep-water oxygen concentration represents a unique whole-lake experiment that can be used to analyze the geochemical response of the sediments.  相似文献   

High-resolution paleoenvironmental studies: an editorial note     

André F. Lotter  Michael Sturm 《Journal of Paleolimnology》1994,11(3):311-312

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Dating of sediments from Lake Zurich (Switzerland) with210Pb and137Cs     

H. N. Erten  H. R. von Gunten  E. Rössler  M. Sturm 《Aquatic Sciences - Research Across Boundaries》1985,47(1):5-11

²¹⁰Pb- and¹³⁷Cs-measurements, and varve counting have been used to date sediment cores from Lake Zurich (Switzerland). Two cores from different water depths were dated with²¹⁰Pb/²¹⁰Po and revealed sediment accumulation rates of (0.055±0.015) g·cm^?2·y^?1 and (0.09±0.03) g·cm^?2·y^?1, respectively. A comparable rate of (0.07±0.01) g·cm^?2·y^?1 has been obtained from¹³⁷Cs measurements. These rates were confirmed by annual layer (varve)-counts which lead to rates of 0.07 g·cm^?2·y^?1. Constant²¹⁰Pb activities were observed in the top 6 cm of the sediment cores. This constancy is generally explained in the literature by mixing processes caused by bioturbation and by distortion during coring operations of the uppermost water-rich fluffy sediments. However the distinct¹³⁷Cs-maxima and the regular and undisturbed varve lamination of the top sediment observed in the cores of Lake Zurich contradict this assumption. In addition, measurements of⁷Be at the water/sediment interaces proved complete sediment core recovery and mechanically undisturbed sediments. Remobilization processes are assumed to cause the observed constant²¹⁰Pb activities. Remobilization may also be the reason for an incomplete²¹⁰Pb inventory in the sediments which contain only about 50% of the fallout from atmosphere. The results of the²¹⁰Pb dating should therefore be considered with some care. If existent, varve counting represents the easiest and most reliable means for dating lake sediments.  相似文献   

Physical model study of Lake Constance     

Kenton M. Stewart  Eckard Hollan 《Aquatic Sciences - Research Across Boundaries》1984,46(1):5-40

This study, carried out at the State University of N.Y. in Buffalo, N.Y. (USA), concerns the construction and operation of a vertically distorted rotating Froude model of Lake Constance and experimentation to determine circulation patterns under both homogeneous and stratified conditions. The model/prototype length ratio equals 1/17,000 and depth ratio 1/650. The rotating model can simulate one prototype day in 2 min 10 s. Briefly the findings indicate: 1. Model seiche periods and decay modulii were equivalent to those in the prototype. 2. Results with the homogeneous model show extreme sensitivity of the model to differing inflow densities. 3. Coriolis effects have a distinct influence on the river-induced circulation. 4. Some aspects of the stratified experiments with wind contrast with earlier interpretations of current patterns. 5. In both the homogeneous and stratified model cases, the effects of wind on circulation patterns dominate over those of the inflowing Alpenrhein. 6. The effects of various wind stress fields were also examined by a two-dimensional mathematical model.  相似文献   

Ein CZCS-Postlaunch-Experiment über der Deutschen Bucht und seine Auswertung im Hinblick auf die dortigen Gelbstoff- und Schwebstoffgehalte sowie die Frontendynamik     

Dr. Hans Gienapp  Dr. Boris Sturm 《Ocean Dynamics》1983,36(3):97-128

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Pyrite-induced hydroxyl radical formation and its effect on nucleic acids   总被引：1，自引：0，他引：1  

Corey A Cohn  Steffen Mueller  Eckard Wimmer  Nicole Leifer  Steven Greenbaum  Daniel R Strongin  Martin AA Schoonen 《Geochemical transactions》2006,7(1):3-11

Background  

Pyrite, the most abundant metal sulphide on Earth, is known to spontaneously form hydrogen peroxide when exposed to water. In this study the hypothesis that pyrite-induced hydrogen peroxide is transformed to hydroxyl radicals is tested.  相似文献   

Distribution of diatoms, chironomids and cladocera in surface sediments of thirty mountain lakes in south-eastern Switzerland   总被引：6，自引：0，他引：6  

Christian Bigler  Oliver Heiri  Renata Krskova  André F. Lotter  Michael Sturm 《Aquatic Sciences - Research Across Boundaries》2006,68(2):154-171

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