Diagenetic Alteration of Magnetic Signals by Anaerobic Oxidation of Methane Related to a Change in Sedimentation Rate   总被引：1，自引：0，他引：1  

Natascha Riedinger  Kerstin Pfeifer  Johanna Fredrika Lukina Garming  Christian Hensen 《Geochimica et cosmochimica acta》2005,69(16):4117-4126

Geochemical and rock magnetic investigations of sediments from three sites on the continental margin off Argentina and Uruguay were carried out to study diagenetic alteration of iron minerals driven by anaerobic oxidation of methane (AOM). The western Argentine Basin represents a suitable sedimentary environment to study nonsteady-state processes because it is characterized by highly dynamic depositional conditions. Mineralogic and bulk solid phase data document that the sediment mainly consists of terrigenous material with high contents of iron minerals. As a typical feature of these deposits, distinct minima in magnetic susceptibility (κ) are observed. Pore water data reveal that these minima in susceptibility coincide with the current depth of the sulfate/methane transition (SMT) where HS⁻ is generated by the process of AOM. The released HS⁻ reacts with the abundant iron (oxyhydr)oxides resulting in the precipitation of iron sulfides accompanied by a nearly complete loss of magnetic susceptibility. Modeling of geochemical data suggest that the magnetic record in this area is highly influenced by a drastic change in mean sedimentation rate (SR) which occurred during the Pleistocene/Holocene transition. We assume that the strong decrease in mean SR encountered during this glacial/interglacial transition induced a fixation of the SMT at a specific depth. The stagnation has obviously enhanced diagenetic dissolution of iron (oxyhydr)oxides within a distinct sediment interval. This assumption was further substantiated by numerical modeling in which the mean SR was decreased from 100 cm kyr⁻¹ during glacial times to 5 cm kyr⁻¹ in the Holocene and the methane flux from below was fixed to a constant value. To obtain the observed geochemical and magnetic patterns, the SMT must remain at a fixed position for ∼9000 yrs. This calculated value closely correlates to the timing of the Pleistocene/Holocene transition. The results of the model show additionally that a constant high mean SR would cause a concave-up profile of pore water sulfate under steady state conditions.  相似文献   

Modelling of Seepage Water Composition from Experiments with an Acid Soil and a Calcareous Sediment     

Kerstin Michel  Bernard Ludwig 《洁净——土壤、空气、水》2005,33(6):595-604

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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa     

Linnemann  Ulf  Pidal  Agustín Pieren  Hofmann  Mandy  Drost  Kerstin  Quesada  Cecilio  Gerdes  Axel  Marko  Linda  Gärtner  Andreas  Zieger  Johannes  Ulrich  Jens  Krause  Rita  Vickers-Rich  Patricia  Horak  Jana 《International Journal of Earth Sciences》2018,107(3):885-911

International Journal of Earth Sciences - In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such...  相似文献   

Effects of Hypoxia on Fish Survival and Oyster Growth in a Highly Eutrophic Estuary     

Rikke Jeppesen  Miguel Rodriguez  Jenna Rinde  John Haskins  Brent Hughes  Laura Mehner  Kerstin Wasson 《Estuaries and Coasts》2018,41(1):89-98

Human land use activities around estuaries can result in high levels of eutrophication. At Elkhorn Slough estuary, a highly eutrophic California estuary, we investigated the effects of impaired water quality on two stress-tolerant estuarine species, a common fish, the staghorn sculpin, Leptocottus armatus and a foundational invertebrate, the Olympia oyster, Ostrea lurida. We caged the two indicator species at six wetlands with different levels of water quality impairment, four of which had restricted tidal flow. We also recorded water quality parameters simultaneously at all sites using YSI sondes, and sampled nutrients and chlorophyll-a monthly, building on the National Estuarine Research Reserve System-wide Monitoring Program. We found that the monitored environmental variables predicted ecological responses by the indicator species. In particular, we found that the duration and severity of hypoxia were negatively correlated with fish survival and oyster growth. Further, our results corroborate previous studies that artificial tidal restriction leads to increased hypoxia stress. We conclude that large diurnal fluctuations in dissolved oxygen and extended nighttime hypoxia can have lethal and sub-lethal effects even on stress-tolerant organisms in the estuary. While laboratory experiments have often shown such effects, it is relatively rare to demonstrate negative effects of oxygen variation with in situ experiments, which provide stakeholders with concrete evidence for impaired water quality at local wetlands. Tidally restricted sites, which experience the largest fluctuations in dissolved oxygen and longest periods of hypoxia, harbor conditions harmful to vertebrates and invertebrates in the estuary. Reversing the anthropogenically induced low oxygen levels, by restoring more natural tidal exchange and by decreasing agricultural runoff, could improve the survival and growth of important estuarine organisms.  相似文献   

The distribution and relative toxic potential of organic chemicals in a PCB contaminated bay     

Sundberg H  Tjärnlund U  Kerman G  Blomberg M  Ishaq R  Grunder K  Hammar T  Broman D  Balk L 《Marine pollution bulletin》2005,50(2):195-207

For reliable monitoring of environmental improvement, the PCB contaminated bay Orserumsviken on Sweden's Baltic coast was investigated prior to remediation. We examined PCB congener patterns and the relative toxic potential of PCBs in extracts of three matrices: bottom sediment, settling particulate matter and the dissolved phase (obtained from semi-permeable membrane devices). Congener patterns were similar in all matrices. Three fractions were isolated from the extracts: (1) aliphatic and monocyclic aromatic compounds (MAC-fraction), (2) dicyclic aromatic compounds (DAC-fraction), including PCBs, and (3) polycyclic aromatic compounds (PAC-fraction), including PAHs. Total extracts and fractions were injected into newly fertilised rainbow trout eggs. At larval stage, hepatic EROD activities were quantified. Though high, the PCB contamination could explain only an estimated 1-5% of the total EROD induction. The order of EROD induction potential was: total extract > PAC-fraction > DAC-fraction > MAC-fraction in all matrices, suggesting that in Orserumsviken PACs made a larger contribution to the EROD induction potential than PCBs and other DACs.  相似文献   

A numerical model study on the behaviour of Asian summer monsoon and AMOC due to orographic forcing of Tibetan Plateau     

Bijan Fallah  Ulrich Cubasch  Kerstin Prömmel  Sahar Sodoudi 《Climate Dynamics》2016,47(5-6):1485-1495

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Erratum to: A geomorphological seabed classification for the Weddell Sea,Antarctica     

Kerstin Jerosch  Gerhard Kuhn  Ingo Krajnik  Frauke Katharina Scharf  Boris Dorschel 《Marine Geophysical Researches》2016,37(2):143-143

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The compensating effect of glaciers: Characterizing the relation between interannual streamflow variability and glacier cover     

Marit van Tiel  Irene Kohn  Anne F. Van Loon  Kerstin Stahl 《水文研究》2020,34(3):553-568

Meltwater from glaciers is not only a stable source of water but also affects downstream streamflow dynamics. One of these dynamics is the interannual variability of streamflow. Glaciers can moderate streamflow variability because the runoff in the glacierized part, driven by temperature, correlates negatively with the runoff in the non-glacierized part of a catchment, driven by precipitation, thereby counterbalancing each other. This is also called the glacier compensation effect (GCE), and the effect is assumed to depend on relative glacier cover. Previous studies found a convex relationship between streamflow variability and glacier cover of different glacierized catchments, with lowest streamflow variability at a certain optimum glacier cover. In this study, we aim to revisit these previously found curves to find out if a universal relationship between interannual streamflow variability and glacier cover exists, which could potentially be used in a space-for-time substitution analysis. Moreover, we test the hypothesis that the dominant climate drivers (here precipitation and temperature) switch around the suggested optimum of the curve. First, a set of virtual nested catchments, with the same absolute glacier area but varying non-glacierized area, were modelled to isolate the effect of glacier cover on streamflow variability. The modelled relationship was then compared with a multicatchment data set of gauged glacierized catchments in the European Alps. In the third step, changes of the GCE curve over time were analysed. Model results showed a convex relationship and the optimum in the simulated curve aligned with a switch in the dominant climate driver. However, the multicatchment data and the time change analyses did not suggest the existence of a universal convex relationship. Overall, we conclude that GCE is complex due to entangled controls and changes over time in glacierized catchments. Therefore, care should be taken to use a GCE curve for estimating and/or predicting interannual streamflow variability in glacierized catchments.  相似文献   

Signatures of Restoration and Management Changes in the Water Quality of a Central California Estuary     

Alison K. Gee  Kerstin Wasson  Susan L. Shaw  John Haskins 《Estuaries and Coasts》2010,33(4):1004-1024

Coastal managers and policy-makers are concerned with tracking improvements to water quality linked to management changes. Long-term water quality data acquired from two wetland areas in the upper reaches of the Elkhorn Slough estuary in central California were analyzed for signatures of land restoration or water control structure management. Post-restoration averaged NO₃, NH₃, and PO₄ concentrations were 50–70% less than before-restoration concentrations. Assessment of watershed-scale effects revealed that proximity of restoration to sampling locations had almost as strong an effect on water quality as the percentage of land restored relative to watershed size. Results also suggest that restoration of even 1% of an agriculturally intensive watershed such as that of the Elkhorn Slough may result in improvements to water quality. Finally, results indicate that tide gate function can dominate water quality in managed wetlands and must be carefully tracked and managed in the context of estuarine conservation targets.  相似文献   

A short-term decrease in household income inequality in the Sundarbans,Bangladesh, following Cyclone Aila     

Abu Nasar Mohammad Abdullah  Kerstin Katharina Zander  Bronwyn Myers  Natasha Stacey  Stephen Thomas Garnett 《Natural Hazards》2016,83(2):1103-1123

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