Mine water-induced gradients in sediment metals and arcellacean assemblages in a boreal freshwater bay (Petkellahti, Finland)     

Susanna M. Kihlman  Tommi Kauppila 《Journal of Paleolimnology》2009,42(4):533-550

Sediment chemistry and arcellacean community composition were analyzed to study the ecological effects of copper mine-derived acidic and metal-rich waters in a freshwater bay in eastern Finland. To track spatial and temporal changes in the bay, 32 mine-impacted (top) and pre-impact (bottom) samples were analyzed from 16 short sediment cores taken along a transect extending from the pollution source. In addition, short cores from the impacted and reference sites were studied. Recent sediments displayed a geochemical gradient from the inner bay, where mine water is discharged, to the outer bay. Inner bay sites were enriched with C, S, and Fe, whereas Mn was depleted, but has precipitated in the outer bay. Among the heavy metals, Cu, Al, Zn, and Ni concentrations had increased in the inner and mid bay, while Co and Cd concentrations had increased at mid-bay sites. The change from the natural to mine-impacted condition was also seen in faunal gradients. According to ordination and distance measures, the greatest changes in species composition occurred in the inner bay, with fairly small changes in the outer bay. Numerical methods suggested that metals (Cu, Pb, Al, Zn, Cr), redox-sensitive elements (Fe, Mn), organic carbon and nutrients could be related to changes in arcellacean assemblages. Geochemical changes in the impacted core started at ~20 cm with increases in S alternating with peaks in Cr and Mg. Heavy metal concentrations increased markedly at 10 cm, after the active mining period, suggesting the beginning of acid mine drainage. Geochemical changes at ~20 cm were already apparent in the arcellacean assemblages, but the most notable change coincided with the geochemical shift at 10 cm, with signs of decreased pH. Numerical methods suggest that mining-related metals Co, Cu, Zn and Ni co-vary with arcellaceans, but Al appears to behave independently with respect to the species data.  相似文献   

Extraction of Nd isotopes from bulk deep sea sediments for paleoceanographic studies on Cenozoic time scales     

Ellen E. Martin  Susanna W. Blair  George D. Kamenov  Howie D. Scher  Elodie Bourbon  Chandranath Basak  Derrick N. Newkirk 《Chemical Geology》2010,269(3-4):414-431

Nd isotopes preserved in fossil fish teeth and ferromanganese crusts have become a common tool for tracking variations in water mass composition and circulation through time. Studies of Nd isotopes extracted from Pleistocene to Holocene bulk sediments using hydroxylamine hydrochloride (HH) solution yield high resolution records of Nd isotopes that can be interpreted in terms of deep water circulation, but concerns about diagenesis and potential contamination of the seawater signal limit application of this technique to geologically young samples.In this study we demonstrate that Nd extracted from the > 63 μm, decarbonated fraction of older Ocean Drilling Program (ODP) sediments using a 0.02 M HH solution produces Nd isotopic ratios that are within error of values from cleaned fossil fish teeth collected from the same samples, indicating that the HH-extractions are robust recorders of deep sea Nd isotopes. This excellent correlation was achieved for 94 paired fish teeth and HH-extraction samples ranging in age from the Miocene to Cretaceous, distributed throughout the north, tropical and south Atlantic, and composed of a range of lithologies including carbonate-rich oozes/chalks and black shales. The strong Nd signal recovered from Cretaceous anoxic black shale sequences is unlikely to be associated with ferromanganese oxide coatings, but may be derived from abundant phosphatic fish teeth and debris or organic matter in these samples.In contrast to the deep water Nd isotopic signal, Sr isotopes from HH-extractions are often offset from seawater values, suggesting that evaluation of Sr isotopes is a conservative test for the integrity of Nd isotopes in the HH fraction. However, rare earth elements (REE) from the HH-extractions and fish teeth produce distinctive middle REE bulge patterns that may prove useful for evaluating whether the Nd isotopic signal represents uncontaminated seawater. Alternatively, a few paired HH-extraction and cleaned fish teeth samples from each site of interest can be used to verify the seawater composition of the HH-extractions. The similarity between isotopic values for the HH-extraction and fish teeth illustrates that the extensive cleaning protocol applied to fish teeth samples is not necessary in typical, carbonate-rich, deep sea sediments.  相似文献   

Does sediment resuspension by storms affect the fate of polychlorobiphenyls (PCBs) in the benthic food chain? Interactions between changes in POM characteristics, adsorption and absorption by the mussel Mytilus galloprovincialis   总被引：1，自引：0，他引：1  

Franois Charles  Susanna Lopez-Legentil  Antoine Grmare  Jean Michel Amouroux  Martin Desmalades  Gilles Vtion  Karine Escoubeyrou 《Continental Shelf Research》2005,25(19-20):2533

Environmental parameters and gross sedimentation rates (GSR) were monitored at a fixed site located in the Bay of Banyuls-sur-Mer (NW Mediterranean), between March 1997 and April 1998, together with the main biochemical characteristics of both sedimenting and sedimented particulate organic matter (POM). Three storms which occurred during this time period resulted in natural sediment resuspension. This is indicated by the corresponding increase in GSR and a decrease in the enzymatically hydrolysable amino acids/totally hydrolysable amino acids ratio (EHAA/THAA), within the sedimenting POM. Only the strongest storm resulted in (1) a transitory increase in fine-grained particles, (2) concomitant increases in organic carbon, carbohydrates, lipids and THAA, and (3) a decrease in the EHAA/THAA ratio in surficial sediments. For most of the assayed parameters, the values recorded after the December 1997 storm corresponded to extremes for the whole period under study. This emphasises the role of storms in controlling the characteristics of sedimented and sedimenting POM.Ten sediment types, with contrasting biochemical characteristics, were selected for experiments; these were based on the results of the monitoring survey and were used during adsorption and absorption experiments involving ¹⁴C tetrachlorobiphenyl (TCB). Adsorption rates differed significantly between the sediment types, but did not correlate with any of the assayed biochemical parameters. Absorption efficiency by the mussel Mytilus galloprovincialis also differed between the sediment types; it correlated positively with all the assayed biochemical parameters, except lipids. Comparison between the magnitudes of the increase in GSR, together with the decrease in absorption efficiency during resuspension events, suggests that resuspension tends to enhance the transfer of organic pollutants in the benthic food chain.  相似文献   

Characterization of cataclastic shear-zones of the KTB deep drill hole by regression analysis of drill cuttings data     

Helmuth Winter  Susanna Adelhardt  Alexander Jerak  Helmut Küchenhoff 《Geophysical Journal International》2002,150(1):1-9

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Crystal structures of Ca-rich clinopyroxenes on the CaMgSi2O6-Mg2Si2O6 join     

Prof. E. Bruno  Dr. Susanna Carbonin  Dr. G. Molin 《Mineralogy and Petrology》1982,29(4):223-240

Summary The structural changes occurring in the clinopyroxenes with composition Di100, Di90En10 and Di80En20, due to the Ca-Mg substitution in the M2 site, have been studied. Evidence is given that with increasing Mg content a small percentage of the atoms converts from the M2 position to a new M2 position which is solely occupied by Mg. The maximum conversion of M2 to M2 found in this study is 7%. The closest parallel to the M2 geometry is found in the ZnSiO₃ pyroxene (C2/c). The presence of this new site causes significant changes in the tetrahedral configuration, because the M2 atoms are not bonded to 03. The intermediate compositions, Di90En10 and Di80En20, may be thought of as the coexistence of two structural models: diopside and ZnSiO₃ pyroxene (C2/c).

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Kristallstrukturen Ca-reicher Klinopyroxene der CaMgSi₂O₆-Mg₂Si₂O₆-Reihe

Zusammenfassung Es wurden die strukturellen Änderungen von Klinopyroxenen der Zusammensetzungen Di100, Di90En10 und Di80En20, die durch den Mg-Ersatz für Ca verursacht werden, untersucht. Es zeigt sich, daß mit steigendem Mg-Gehalt ein kleiner Teil der Atome der M2-Position zu einer neuen M2-Position wechselt; diese wird ausschließlich durch Mg besetzt. Der größte in dieser Arbeit gefundene Übergang von M2 nach M2 beträgt ca. 7%. Die stärksten Parallelen zur Geometrie um M2 werden im Pyroxen ZnSiO₃ (C2/c) gefunden. Die Besetzung dieser neuen Position verursacht bedeutende Änderungen im Tetraederverband, da die M2-Atome nicht an O3 gebunden sind. Die Pyroxenstrukturen mit den intermediären Zusammensetzungen Di90En10 und Di80En20 können als Überlagerung zweier Modelle betrachtet werden: Diopsid und ZnSiO₃-Pyroxen (C2/c).

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Abbreviations En Enstatite - Di Diopside - Hd Hedenbergite - Fs Ferrosilite - ClEn Clinoenstatite - Di100 pure diopside - Di90 Di90En10 (mol.-%) - Di80 Di80En20 - brg bridging With 6 Figures  相似文献   

Pop-up landscapes: a new trigger to push up land value?     

Susanna Schaller  Sandra Guinand 《Urban geography》2018,39(1):54-74

Through a qualitative analysis of pop-up landscapes on Philadelphia’s Delaware Waterfront, this paper examines how entrepreneurial urban actors, such as municipal officials, urban planning agencies, and landscape designers, strategically harness to catalyze investment. While pop-up landscapes have disrupted negative associations with the waterfront, providing a space for people to reimagine the city and playing an active role as an integrative public space, the paper argues that there are reasons to be skeptical about the long-term goals the pop-up landscapes serve, given the widespread focus on real estate-led development.  相似文献   

The impact of trout introductions on macro- and micro-invertebrate communities of fishless boreal lakes     

Marco Milardi  Susanna Siitonen  Jyrki Lappalainen  Anne Liljendahl  Jan Weckström 《Journal of Paleolimnology》2016,55(3):273-287

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Constraints on the state of in situ effective stress and the mechanical behavior of ODP Leg 186 claystones in the Japan Trench forearc     

Maria Vera Susanna Ask  Achim Kopf 《Island Arc》2004,13(1):242-257

Abstract The Japan Trench forearc offshore Honshu Island in northeast Japan, where the 130‐m.y.‐old Pacific oceanic plate is presently subducted, was drilled during the Ocean Drilling Program Leg 186. Results from mechanical and sedimentological studies of claystones recovered from Sites 1150 and 1151 in the overlying erosional forearc wedge are reported in the present study. Although many physical properties are similar in the seismic (Site 1150) and aseismic portion (Site 1151) of the shallow forearc, Site 1150 displayed a higher abundance of open fractures, two prominent fault zones and enigmatic pore fluid signatures in the claystones. The abundance of weak mineral phases, together with high smectite contents (from X‐ray diffraction), control the low friction coefficients of 0.33–0.39 of the claystones in ring‐shear experiments. Results from triaxial testing proposed overall low magnitudes of in situ effective vertical stress, with somewhat lower values at Site 1150 than at Site 1151. Similarly, samples from Site 1150 displayed slightly higher pore fluid pressures than those at Site 1151. The high sediment porosities, which are in part also a result of intact diatom tests (from scanning electron microscope), together with the anomalous fluid signatures and elevated pore fluid pressures, could very likely result from upward migration and influx of deep‐seated waters. Dewatering reactions at depth result in enhanced pore fluid pressure transients along out‐of‐sequence thrusts and consequently lower effective stress. At depths greater than that of Leg 186 drilling, elevated pressure–temperature conditions trigger mineral transformation and cementation, which result in increasing friction, unstable sliding and seismic rupture. Such earthquakes could have repeatedly disaggregated the consolidated claystone fabrics at the seismic site, and could be responsible for differences in yield strength and cementation when compared to the aseismic Site 1151.  相似文献   

Enhancing preparedness for managing debris from earthquakes: lessons from Italy     

Modica  Marco  Paleari  Susanna  Rampa  Andrea 《Natural Hazards》2021,105(2):1395-1412

Natural Hazards - Earthquakes can generate large volumes of debris which may threaten public health, hinder reconstruction and impact the environment. The present paper aims at investigating how...  相似文献   

Cost–benefit analysis of flood mitigation measures: a case study employing high-performance hydraulic and damage modelling     

Molinari  Daniela  Dazzi  Susanna  Gattai  Edoardo  Minucci  Guido  Pesaro  Giulia  Radice  Alessio  Vacondio  Renato 《Natural Hazards》2021,108(3):3061-3084

Natural Hazards - This paper shows a detailed, advanced procedure to implement cost–benefit analyses (CBAs) in order to assess the effectiveness of flood mitigation measures. The town of Lodi...  相似文献