Fortress Wytschaete: geological controls on the German frontline in Flanders, 1914–1917     

Peter Doyle  Simon Verdegem  Robin Schäfer 《Geology Today》2020,36(2):64-74

The Battle of Messines (Wytschaete Bogen) of June 1917 is hailed as a triumph of military geology, with the simultaneous explosion of some 19 mines leading to the Allied destruction of the German frontline positions. This story is well known and rightly celebrated; but less well understood and often overshadowed by this success is the story of the effectiveness of the German fortress positions. These were constructed in late 1914 in order to maintain the strategic aim of holding the Allies in the west while pressing the Russians through a series of offensives in east. In this, they were highly effective, even in the face of continuous Allied bombardment. This article seeks to redress this unbalance in our understanding, drawing on archaeological evidence and archival resources to present a clearer picture of the nature of the German positions.  相似文献   

Application of linear stochastic models for drought forecasting in the Büyük Menderes river basin, western Turkey   总被引：6，自引：3，他引：3  

Ömer Faruk Durdu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(8):1145-1162

In the present study, a seasonal and non-seasonal prediction of the Standardized Precipitation Index (SPI) time series is addressed by means of linear stochastic models. The methodology presented here is to develop adequate linear stochastic models known as autoregressive integrated moving average (ARIMA) and multiplicative seasonal autoregressive integrated moving average (SARIMA) to predict drought in the Büyük Menderes river basin using SPI as drought index. Temporal characteristics of droughts based on SPI as an indicator of drought severity indicate that the basin is affected by severe and more or less prolonged periods of drought from 1975 to 2006. Therefore, drought prediction plays an important role for water resources management. ARIMA modeling approach involves the following three steps: model identification, parameter estimation, diagnostic checking. In model identification step, considering the autocorrelation function (ACF) and partial autocorrelation function (PACF) results of the SPI series, different ARIMA models are identified. The model gives the minimum Akaike Information Criterion (AIC) and Schwarz Bayesian Criterion (SBC) is selected as the best fit model. Parameter estimation step indicates that the estimated model parameters are significantly different from zero. Diagnostic check step is applied to the residuals of the selected ARIMA models and the results indicated that the residuals are independent, normally distributed and homoscedastic. For the model validation purposes, the predicted results using the best ARIMA models are compared to the observed data. The predicted data show reasonably good agreement with the actual data. The ARIMA models developed to predict drought found to give acceptable results up to 2 months ahead. The stochastic models developed for the Büyük Menderes river basin can be employed to predict droughts up to 2 months of lead time with reasonably accuracy.  相似文献   

Diatom assemblage dynamics during abrupt climate change: the response of lacustrine diatoms to Dansgaard–Oeschger cycles during the last glacial period     

Linda Ampel  Barbara Wohlfarth  Jan Risberg  Daniel Veres  Melanie J. Leng  Päivi Kaislahti Tillman 《Journal of Paleolimnology》2010,44(2):397-404

The sedimentary record from the paleolake at Les Echets in eastern France allowed a reconstruction of the lacustrine response to several abrupt climate shifts during the last glacial period referred to as Dansgaard–Oeschger (DO) cycles. The high-resolution diatom stratigraphy has revealed distinct species turnover events and large fluctuations in stable oxygen isotope values in diatom frustules, as a response to DO climate variability. More or less identical species compositions became re-established during each DO stadial and interstadial phases, respectively. However, the relative abundance of the most dominant species within these assemblages varies and might indicate differences in climatic conditions. Interstadial phases are characterized by identical species successions. Transitions from stadial to interstadial conditions show a distinct Fragilaria–Cyclotella succession, which resembles the diatom regime shifts that have been recognized in some lakes in the Northern Hemisphere since the mid-nineteenth century.  相似文献   

Biomarker and stable carbon isotope analyses of sedimentary organic matter from Lake Tswaing: evidence for deglacial wetness and early Holocene drought from South Africa     

I. Kristen  H. Wilkes  A. Vieth  K.-G. Zink  B. Plessen  J. Thorpe  T. C. Partridge  H. Oberhänsli 《Journal of Paleolimnology》2010,44(1):143-160

Comparing the organic matter (OM) composition of modern and past lake sediments contributes to the understanding of changes in lacustrine environments over time. We investigate modern plant and lake-water samples as well as modern and ancient sediment samples from the Tswaing Crater in South Africa using biomarker and stable carbon isotope analyses on bulk OM and specific biomarker compounds. The characteristic molecular markers for higher land plants (predominantly C3-type deciduous angiosperms) in Lake Tswaing are long-chain n-alkanes (n-C₂₇₋₃₃), n-alkanols (n-C₂₈₊₃₀), stigmasterol, β-sitosterol, β-amyrin, α-amyrin and lupeol. The C₁₇ n-alkane, tetrahymanol, gammaceran-3-one and C₂₉ sterols dominate the lipid fraction of autochthonously produced OM. By comparing stable carbon isotope analyses on bulk OM and the characteristic biomarkers, we follow the modern carbon cycle in the crater environment and find indications for methanotrophic activity in the lake from isotopically depleted moretene. A comparative study of core sediments reveals changes in the terrestrial (C3 versus C4) and aquatic bioproductivity and allows insights into the variability of the carbon cycle under the influence of changing climatic conditions for the time from the end of the last glacial (Termination I) to the late Holocene, ca. 14,000–2,000 calibrated years before present (years BP). The most pronounced changes occur in the aquatic realm after ca. 10,000 years BP when our results imply climate swings from more humid to more arid and after 7,500 years BP to gradually more humid conditions again, which can be related to a shift in the position of the Inter-Tropical Convergence Zone or to changes in the tropical atmosphere–ocean interaction. Long-chain alkenones (LCAs) have been identified in ancient lake sediments from Africa for the first time. They occur in samples older than 7,500 years BP and their distribution (dominance of C₃₈ and of tri- over tetra-unsaturated LCAs) is distinctly different from other published records suggesting a to date unknown source organism.  相似文献   

Trace metal and geochemical variability during 5,500 years in the sediment of Lake Lehmilampi,Finland     

Anna Augustsson  Pasi Peltola  Bo Bergbäck  Timo Saarinen  Eeva Haltia-Hovi 《Journal of Paleolimnology》2010,44(4):1025-1038

A high-resolution geochemical profile from a 5,500-year-old sediment core of Lake Lehmilampi in eastern Finland was analyzed to study long-term trends and variability in element concentrations and accumulation rates. The accumulation rates of all studied elements followed the same trend, responding to changes in the total sedimentation rate. Concentration profiles differed among elements and showed considerable variation over time. Principal components analysis (PCA) was used on the concentration data to identify groups of elements that have similar geochemical controls. The first principal component was influenced by changes in mineral matter accumulation, and it incorporated elements that are associated with stable allochthonous minerals (such as Mg, K, Cs, Rb, Li, Ti and Ga), as well as elements in forms that become diluted when mineral matter increases (e.g., S, Fe and Mn). The second and third principal components showed that a large proportion of the variance was accounted for by elements with continuously increasing or decreasing concentrations related to pedogenetical development of the catchment soil. In the case of Hg, Pb and Cd, however, accumulation rates increased faster at the surface than is simply accounted for by changes in total sedimentation rates. For Cu, Cr, Ni and Zn, concentrations increased over the past 150 years, but there were no indications of a significant addition due to atmospheric deposition. These elements had more variable concentrations before the mid nineteenth century than after, as did elements that are often used for normalization. These findings suggest that lake sediments may not properly reflect the history of atmospheric metal deposition in remote areas.  相似文献   

Effect of Different Nanomaterials on the Metabolic Activity and Bacterial Flora of Activated Sludge Medium          下载免费PDF全文

Tülay Ergön‐Can  Derya Y. Köseoğlu‐İmer  Ömer Faruk Algur  İsmail Koyuncu 《洁净——土壤、空气、水》2016,44(11):1508-1515

  相似文献   

What governs macrophyte species richness in kettle hole types? A case study from Northeast Germany     

Marlene Pätzig  Thomas Kalettka  Michael Glemnitz  Gert Berger 《Limnologica》2012,42(4):340-354

Kettle holes are small, pond-like, depressional wetlands in young moraine landscapes. They mostly undergo a wet-dry cycle and have a high potential for biological species diversity. However, their biodiversity and habitat function is often greatly impacted by surrounding intensive agricultural land use practices.In this study, we used statistical analysis of a large data set from the federal state of Brandenburg (Northeast Germany) to characterise the macrophyte species richness of kettle holes in an interregional context and to determine the factors that influence macrophyte occurrence. We proposed that (1) specific environmental factors, (2) hydrogeomorphic kettle hole types and (3) the regional topography have a major impact on macrophyte species richness. The evaluation of the data was performed using the General Linear Model (GLM) and Canonical Correspondence Analysis (CCA). Each of the analysed factors addresses different parts of the macrophyte species richness, including the target variables overall species richness, plant life and growth forms as well as Red List species.None of the analysis showed effects of the tested environmental factors on overall macrophytes species richness, but on the richness of plant life and growth forms as well as on Red List species. We identified hydroperiod, depth, shore width, kettle hole area, pH, electric conductivity, carbonate hardness and oxygen as key factors for the prediction of species richness of plant life and growth forms. Furthermore, we demonstrate that hydrogeomorphic kettle hole types account for relevant parts of variation in species richness and are useful interregional and integrative indicators to identify kettle holes with protection priority for macrophytes.  相似文献   

Why the <Emphasis Type="Italic">Euler</Emphasis> scheme in particle tracking is not enough: the shallow-sea pycnocline test case     

Ulf Gräwe  Eric Deleersnijder  Syed Hyder Ali Muttaqi Shah  Arnold Willem Heemink 《Ocean Dynamics》2012,62(4):501-514

During the last decades, the Euler scheme was the common “workhorse” in particle tracking, although it is the lowest-order approximation of the underlying stochastic differential equation. To convince the modelling community of the need for better methods, we have constructed a new test case that will show the shortcomings of the Euler scheme. We use an idealised shallow-water diffusivity profile that mimics the presence of a sharp pycnocline and thus a quasi-impermeable barrier to vertical diffusion. In this context, we study the transport of passive particles with or without negative buoyancy. A semi-analytic solutions is used to assess the performance of various numerical particle-tracking schemes (first- and second-order accuracy), to treat the variations in the diffusivity profile properly. We show that the commonly used Euler scheme exhibits a poor performance and that widely used particle-tracking codes shall be updated to either the Milstein scheme or second-order schemes. It is further seen that the order of convergence is not the only relevant factor, the absolute value of the error also is.  相似文献   

Assessment of Water Quality in the Elbe River at Flood Water Conditions Based on Cluster Analysis,Principle Components Analysis,and Source Apportionment     

Martina Baborowski  Vasil Simeonov  Jürgen W. Einax 《洁净——土壤、空气、水》2012,40(4):373-380

An assessment of water quality measurements during a spring flood in the Elbe River is presented. Daily samples were taken at a site in the middle Elbe, which is part of the network of the International Commission for the Protection of the Elbe River (IKSE/MKOL). Cluster analysis (CA), principal components analysis (PCA), and source apportionment (APCS apportioning) were used to assess the flood‐dependent matter transport. As a result, three main components could be extracted as important to the matter transport in the Elbe River basin during flood events: (i) re‐suspended contaminated sediments, which led to temporarily increased concentrations of suspended matter and of most of the investigated heavy metals; (ii) water discharge related concentrations of pedogenic dissolved organic matter (DOM) as well as preliminary diluted concentrations of uranium and chloride, parameters with stable pollution background in the river basin; and (iii) abandoned mines, i.e., their dewatering systems, with particular influence on nickel, manganese, and zinc concentrations.  相似文献   

Product Evaluation for the Control of Chemical Emissions to Indoor Air – 10 Years of Experience with the AgBB Scheme in Germany     

Christine Däumling 《洁净——土壤、空气、水》2012,40(8):779-789

Emissions from construction products may have a significant impact on the quality of indoor air, particularly in energy‐efficient buildings, where the normal rate of air exchange with fresh ambient air may be limited. In this context, reduction strategies to mitigate the concentration of chemicals in the indoor environment have become even more important. German authorities wanted to foster the development of low‐emission products, and as a result it was necessary to quantify and qualify these emissions in a reliable and objective manner. The core principles for evaluation of the standardized measurements in emission tests were established by the “Committee for Health‐Related Evaluation of Building Products” (AgBB) and published in the so‐called “AgBB scheme”. Relevant for evaluation are: (i) Assessment of the emission levels of substances with known toxicological properties; (ii) limits for non‐assessable or unknown substances; (iii) limits for the total amount of chemical emissions. This review describes the stepwise implementation of the test procedure in Germany and the experience gained in evaluation of product emissions over the years. A comprehensive overview of the philosophy, history, current practices, and future directions of the German AgBB scheme for VOC emissions is also provided. Special emphasis is given to the evaluation of a list of about 170 single substances which have an agreed “lowest concentration of interest” (LCI) value for the indoor environment – values that are updated periodically according to present toxicological knowledge.  相似文献