A method to detect and characterize sub‐daily flow fluctuations          下载免费PDF全文

Franz Greimel  Bernhard Zeiringer  Norbert Höller  Bettina Grün  Reinhold Godina  Stefan Schmutz 《水文研究》2016,30(13):2063-2078

Hydro peaking causes an important environmental impact on running water ecosystems. Many affected rivers have a poor ecological status. In rivers affected by hydro peaking, the flow conditions are highly complex and difficult to grasp. To develop a general framework for detecting and characterizing sub‐daily flow fluctuations, we analysed more than 500 Austrian hydrographs, covering the whole range from unimpacted to heavily impacted rivers. Different fluctuation types could be identified according to the potential source: e.g. sub‐daily flow fluctuations caused by hydro peaking, rainfall or snow and glacier melt. Additionally, the term ‘hydro fibrillation’ was established, to indicate frequently occurring artificial fluctuations with comparably low intensities. An automatic procedure was used to detect frequency and intensity of each flow fluctuation. Using variables based on duration curves of flow fluctuation rates (ramping rates), amplitudes, flow ratios, durations and daily numbers of fluctuations, a predictive model (linear discriminant analysis) was fitted to classify hydrographs into predominant fluctuation regimes. This is the basis for a detailed investigation of present sub‐daily flow regimes and to analyse the differences between the regimes. Based on the results, we finally propose a general framework that enables a standardized assessment of flow fluctuations regarding event intensities and/or event timing. The proposed framework offers a standardized selection of particular flow fluctuations referring to increase and decrease events separately. The selection of specific flow fluctuations can be defined with respect to several research questions (e.g. ecologically relevant fluctuations), which offers a wide range of applications. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Spatial and temporal variability of widespread dark production and decay of hydrogen peroxide in freshwater     

Ryan M. Marsico  Robin J. Schneider  Bettina M. Voelker  Tong Zhang  Julia M. Diaz  Colleen M. Hansel  Shuichi Ushijima 《Aquatic Sciences - Research Across Boundaries》2015,77(4):523-533

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Ein 100-l-Glaskugelschöpfer zur kontaminationsfreien Entnahme von Seewasser für die Analyse lipophiler organischer Stoffe     

Dr. Norbert Theobald  Wilfried Lange  Andrea Rave  Ulrich Pohle  Peter Koennecke 《Ocean Dynamics》1990,43(6):311-322

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Micro- and macronutrients in the southeastern Bering Sea: Insight into iron-replete and iron-depleted regimes   总被引：2，自引：0，他引：2  

Ana M. Aguilar-Islas  Matthew P. Hurst  Bettina Sohst  Maeve C. Lohan 《Progress in Oceanography》2007,73(2):99-126

Surface transects and vertical profiles of macronutrients, dissolved iron (D-Fe), and dissolved manganese (D-Mn) were investigated during August 2003 in the southeastern Bering Sea. We observed iron-limited, HNLC surface waters in the deep basin of the Bering Sea (15-20 μmol/kg nitrate, ∼0.07 nmol/kg D-Fe, and ?1.0 nmol/kg D-Mn); nitrate-limited, iron-replete surface waters over the shelf (<0.1 μmol/kg nitrate, 0.5-4 nmol/kg D-Fe, and 2-33 nmol/kg D-Mn); and high biomass at the shelf break (“Green Belt”), where diatoms appeared to have been stressed by low D-Fe concentrations (<0.3 nmol/kg). Sources of nitrate and iron to the Green Belt were investigated. A mixture of Aleutian North Slope Current water (with elevated, but non-sufficient iron concentrations relative to its high nitrate concentrations) and surface waters from the vicinity of the Bering Canyon (with lower nitrate concentrations, but similar dissolved iron concentrations) was carried along the shelf break by the Bering Slope Current. This water mixture provided macro- and micronutrients at the southern end of the shelf break. The oceanic domain supplied additional macronutrients to Green Belt waters, while the bottom layer of the outer shelf domain supplied additional macro- and micronutrients through enhanced vertical mixing at the shelf break. Surface waters near the Pribilof Islands, where the highest surface D-Fe concentrations were observed (∼5-6 nmol/kg), represent a potential source of additional iron to Green Belt waters. During summer, the subsurface water of the middle shelf domain is a potential source of nitrate to the nitrate depleted waters of the shelf. In this subsurface cool pool, we observed evidence of substantial denitrification with lower than expected nitrate concentrations.  相似文献   

Matrilineal evidence for genetic structure and Late Pleistocene demographic expansion of the Ornate goby Istigobius ornatus (Teleostei: Gobiidae) in the Persian Gulf and Oman Sea     

Reza Sadeghi  Hamid Reza Esmaeili  Fatah Zarei  Bettina Reichenbacher 《Marine Ecology》2021,42(1):e12629

The Persian Gulf and Oman Sea are characterized by an interesting paleoclimatic history and different ecological settings, and offer a unique study area to investigate the genetic structure of marine organisms including fishes. The Ornate goby Istigobius ornatus is widely distributed throughout the tropical Indo‐West Pacific including the Persian Gulf and Oman Sea. Here, we present the population structure, genetic diversity, and demographic history of four populations of I. ornatus from the latter two regions using the D‐loop marker of mitochondrial DNA. The results reveal a shallow genealogy, a star‐like haplotype network, significance of neutrality tests, and unimodal mismatch distribution. This is concordant with a recent demographic expansion of I. ornatus in the Persian Gulf and Oman Sea at about 63,000–14,000 years ago, which appears to be related to Late Pleistocene sea level fall and rise. The results of the pairwise Fst estimates imply high gene flow along the coast of the Persian Gulf, which is probably due to larval dispersion, whereas the Oman Sea population clearly differs from all Persian Gulf populations. The AMOVA result indicates that 7.74% of the variation is related to differences among ecoregions, while inter‐ and intra‐population differences explained ?3.20% and 95.47% of the variation, respectively. The haplotype network depicts two groups of haplotypes, most of them were specific to the Persian Gulf. No further evidence for geographic lineage substructuring was evident. The Mantel test result indicates that isolation by distance is not the main mechanism that promoted the genetic differentiation among the studied populations of I. ornatus. We suggest that cumulative effects of ecological and geographic barriers such as salinity, oceanographic conditions, and the presence of the Strait of Hormuz have shaped the genetic structure of I. ornatus in the Persian Gulf and Oman Sea.  相似文献   

Interpretation of metal speciation data in coastal waters: the effects of humic substances on copper binding as a test case     

Bettina M. Voelker  Megan B. Kogut 《Marine Chemistry》2001,74(4)

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A new magnetostratigraphic framework for the Lower Miocene (Burdigalian/Ottnangian, Karpatian) in the North Alpine Foreland Basin     

Bettina Reichenbacher  Wout Krijgsman  Yannick Lataster  Martina Pippèrr  Christiaan G. C. Van Baak  Liao Chang  Daniel Kälin  Jürg Jost  Gerhard Doppler  Dietmar Jung  Jérôme Prieto  Hayfaa Abdul Aziz  Madelaine Böhme  Jennifer Garnish  Uwe Kirscher  Valerian Bachtadse 《Swiss Journal of Geoscience》2013,106(2):309-334

Oligocene–Miocene chronostratigraphic correlations within the Paratethys domain are still highly controversial. This study focuses on the late Early Miocene of the Swiss and S-German Molasse Basin (Late Burdigalian, Ottnangian–Karpatian). Previous studies have published different chronologies for this time interval that is represented by the biostratigraphically well constrained Upper Marine Molasse (OMM, lower and middle Ottnangian), Upper Brackish Molasse (OBM, Grimmelfingen and Kirchberg Formations, middle and upper Ottnangian to lower Karpatian, MN 4a–MN 4b) and Upper Freshwater Molasse (OSM, Karpatian–Badenian, MN 5). Here, we suggest a new chronostratigraphic framework, based on integrated magneto-litho-biostratigraphic studies on four sections and three boreholes. Our data indicate that the OBM comprises chrons 5D.1r and 5Dn (Grimmelfingen Fm), chron 5Cr (lower Kirchberg Fm) and the oldest part of chron 5Cn.3n (upper Kirchberg Fm). The OSM begins during chron 5Cn.3n, continues through 5Cn, and includes a long reversed segment that can be correlated to chron 5Br. The OMM-OSM transition was completed at 16.0 Ma in the Swiss Molasse Basin, while the OBM-OSM changeover ended at 16.6 Ma in the S-German Molasse Basin. As the lower Kirchberg Fm represents a facies of the Ottnangian, our data suggest that the Ottnangian–Karpatian boundary in the Molasse Basin is approximately at 16.8 Ma, close to the 5Cr–5Cn.3n magnetic reversal, and thus 0.4 Myr younger than the inferred age of 17.2 Ma used in recent Paratethys time scales. Notably, this would not be problematic for the Paratethys stratigraphy, because chron 5Cr is mainly represented by a sedimentation gap in the Central Paratethys. We also realise, however, that additional data is still required to definitely solve the age debate concerning this intriguing time interval in the North Alpine Foreland Basin. We dedicate this work to our dear friend and colleague Jean-Pierre Berger (8 July 1956–18 January 2012).  相似文献   

放牧强度对内蒙古半干旱草原地气间能量和物质交换的影响   总被引：2，自引：1，他引：1  

王雷  刘辉志  KETZER Bettin 《大气科学》2009,33(6):1201-1211

利用涡度相关技术, 于2006年7月27日至8月10日在内蒙古半干旱草原三种放牧强度的下垫面进行微气象观测。本文分析了放牧强度对内蒙古半干旱草原地气间能量和物质交换的影响, 发现: (1)放牧降低植被覆盖率, 使地表反射率增大。(2)放牧使潜热通量减小。而放牧强度最大的锡林河河道潜热通量最大,表明土壤水分状况是半干旱草原地表能量收支的决定性因素。(3)羊草和冬季放牧观测点日平均CO2通量分别为-1.92 g?m-2?d-1和0.73 g?m-2?d-1, 表明放牧可以使草地由CO2的汇转变为源。锡林河河道为CO2的汇, 日平均CO2通量-3.35 g?m-2?d-1, 与羊草比较, 锡林河河道吸收CO2更多, 表明土壤湿度是影响半干旱草原CO2通量交换的重要因素。(4) 放牧通过减小叶面积指数, 减弱植被的光合作用能力。  相似文献   

The hafnium isotope composition of Pacific Ocean water   总被引：1，自引：0，他引：1  

Bettina Zimmermann  Martin Frank  Der-Chuen Lee 《Geochimica et cosmochimica acta》2009,73(1):91-5926

The first Hf isotope data for seawater are reported for a series of stations in the Northwestern Pacific and define a range from ε_Hf = 3.5 ± 1.4 to 8.6 ± 1.6. Most samples have values within error of the average of ε_Hf = 5.9, but significant variations are found in intermediate waters at a depth of 600 m, as well as in deep waters. The Nd and Hf isotope compositions of the deep waters fall within the range of values found for surfaces of hydrogenetic ferromanganese crusts in the region, confirming that Hf in the Fe-Mn crusts has been derived from the overlying water column, which thus provide an archive of past seawater compositions. Although the seawater samples are generally close to the global ε_Nd-ε_Hf correlation obtained from ferromanganese crusts, there are significant deviations from this correlation indicating that there is some additional decoupling between Nd and Hf isotope signals, most likely caused by local water mass mixing and differences in residence times. This is not resolved in the crust samples, which integrate seawater signals over 10⁴ years. The combined use of these two isotope systems in seawater therefore provides an additional dimension for tracing water masses in the oceans. Studies of the distribution of oceanic Hf isotope compositions that have been confined to deep water and boundary waters, as recorded in seafloor ferromanganese crusts, can now be extended and aimed at characterising the entire present-day water column. Average Hf concentrations measured in this study are somewhat lower than previously reported, suggesting a shorter residence time for Hf in the global oceans, although the uncertainty in the extent of Hf removal from the water column during estuarine mixing as well as a lack of data on hydrothermal and dust inputs remains a limit on how well the residence time can be defined.  相似文献   

Dynamics of explosive volcanism at Unzen volcano: an experimental contribution     

Bettina Scheu  Oliver Spieler  Donald B. Dingwell 《Bulletin of Volcanology》2006,69(2):175-187

Knowledge of the dynamics of magma fragmentation is necessary for a better understanding of the explosive behaviour of silicic volcanoes. Here we have measured the fragmentation speed and the fragmentation threshold of five dacitic samples (6.7–53.5 vol% open porosity) from Unzen volcano, Kyushu, Japan. The measurements were carried out using a shock-tube-based fragmentation apparatus modified after Alidibirov and Dingwell (1996a,b). The results of the experimental work confirm the dominant influence of porosity on fragmentation dynamics. The velocity of the fragmentation front increases and the value of the fragmentation threshold decreases with increasing porosity. Further, we observe that the fragmentation speed is strongly influenced by the initial pressure difference and the texture of the dacite. At an initial pressure difference of 30 MPa, the fragmentation speed varies from 34 m/s for the least porous sample to 100 m/s for the most porous sample. These results are evaluated by applying them to the 1990–1995 eruptive activity of Unzen volcano. Emplacements of layered lava dome lobes, Merapi-type pyroclastic flows and minor explosive events dominated this eruption. The influence of the fragmentation dynamics on dome collapse and Vulcanian events is discussed.  相似文献