Distribution of metals in sediments of the elbe estuary in 1994

1998 ◽  
Vol 37 (6-7) ◽  
pp. 109-116 ◽  
Author(s):  
Alexander Groengroeft ◽  
Ursula Jaehnig ◽  
Guenter Miehlich ◽  
Rolf Lueschow ◽  
Vera Maass ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Fraction ◽  
Outer Part ◽  
Quality Criteria ◽  
Total Sample ◽  
Enrichment Factors ◽  
Contamination Level ◽  
Sediment Layer ◽  
Elbe Estuary ◽  
Fine Grained

In 1994 the quality of the uppermost sediment layer of the Elbe estuary was surveyed for various planning purposes. For example, metal contents were determined in the grain-size fraction <20 μm, and the concentrations of PAH were analyzed in the total sample, with correcting for grain-size effect being done numerically. Using the specific zinc contents in fine-grained particles, transport phenomena were recognized: particles of marine origin are transported >100 km upstream to the Hamburg area, causing contamination to decrease to about 50% of the fluvial level. The local metal contamination however varies strongly. Samples with low concentration could be detected as geogen; the samples with the highest level of contamination were assumed to have originated from periods of higher river pollution. Of the samples, 74% with medium enrichment factors (2 to 8.5 vs. background for Zn) were suspected to reflect the actual contamination level. Compared to previously reported quality criteria, sediment samples from the upper part of the estuary are still highly contaminated. In the outer part of the estuary the quality is better, but because the marine fine-grained particles still have contamination levels to class II-III in the ARGE Elbe classification system, a further reduction of sediment contamination in the whole estuary would be limited to this level.

scholarly journals Image analysis for measuring the size stratification in sand–gravel laboratory experiments

2014 ◽  
Vol 2 (1) ◽  
pp. 217-232 ◽  
Author(s):  
C. Orrú ◽  
V. Chavarrías ◽  
W. S. J. Uijttewaal ◽  
A. Blom
Keyword(s):  
Grain Size ◽  
Image Analysis ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Measurement Method ◽  
Laboratory Experiments ◽  
Size Fraction ◽  
Sediment Layer ◽  
Areal Fraction ◽  
Sediment Layers

Abstract. Measurements of spatial and temporal changes in the grain-size distribution of the bed surface and substrate are crucial to improving the modelling of sediment transport and associated grain-size selective processes. We present three complementary techniques to determine such variations in the grain-size distribution of the bed surface in sand–gravel laboratory experiments, as well as the resulting size stratification: (1) particle colouring, (2) removal of sediment layers, and (3) image analysis. The resulting stratification measurement method was evaluated in two sets of experiments. In both sets three grain-size fractions within the range of coarse sand to fine gravel were painted in different colours. Sediment layers are removed using a wet vacuum cleaner. Subsequently areal images are taken of the surface of each layer. The areal fraction content, that is, the relative presence of each size fraction over the bed surface, is determined using a colour segmentation algorithm which provides the areal fraction content of a specific colour (i.e. grain size) covering the bed surface. Particle colouring is not only beneficial to this type of image analysis but also to the observation and understanding of grain-size selective processes. The size stratification based on areal fractions is measured with sufficient accuracy. Other advantages of the proposed size stratification measurement method are (a) rapid collection and processing of a large amount of data, (b) a very high spatial density of information on the grain-size distribution, (c) the lack of disturbances to the bed surface, (d) only minor disturbances to the substrate due to the removal of sediment layers, and (e) the possibility to return a sediment layer to its original elevation and continue the flume experiment. The areal fractions are converted into volumetric fractions using an existing conversion model.

scholarly journals Inverse Relationship of Marine Aerosol and Dust in Antarctic Ice with Fine-Grained Sediment in the South Atlantic Ocean: Implications for Sea-Ice Coverage and Wind Strength

2012 ◽  
Vol 3 (1) ◽  
pp. 1-15
Author(s):  
Sharon L. Kanfoush
Keyword(s):  
Grain Size ◽  
Sea Ice ◽  
Size Fraction ◽  
Inverse Correlation ◽  
Light Limitation ◽  
Marine Aerosol ◽  
Biological Productivity ◽  
Fine Grained ◽  
Fine Sediments ◽  
Natural Gamma

This research seeks to test the hypothesis that natural gamma radiation (NGR) from Ocean Drilling Program Site 1094, which displays variability over the last glacial-interglacial cycle similar to dust in the Vostok ice core, reflects fine-grained terrigenous sediment delivered by eolian processes. Grain size was measured on 400 samples spanning 0–20 m in a composite core. Accumulation of the <63μ size fraction at Site 1094 and dust in Vostok exhibit a negative correlation, suggesting the fine sediments are not dominantly eolian. However the technique used for grain size measurements cannot distinguish between terrigenous and biogenous materials; therefore it is possible much fine-grained material is diatoms. An inverse correlation between fine sediments and NGR supports this interpretation, and implies terrigenous materials were at times diluted by microfossils from high biological productivity. Fine marine sediments correlate positively with temperature and negatively with marine aerosol Na+ in Vostok. One plausible explanation is extensive sea-ice of cold intervals steepened ocean-continent temperature gradients, intensified winds, and led to increased transport of dust and marine aerosol to Antarctica yet also reduced biological productivity at Site 1094. Such a reduction despite increases in NGR, potentially representing Fe-rich dust influx, would require light limitation or stratification associated with sea-ice.

Dating Bulk Sediments from Limnic Deposits Using a Grain-Size Approach

Radiocarbon ◽  
2013 ◽  
Vol 55 (2) ◽  
pp. 943-950 ◽  
Author(s):  
Leo Rothacker ◽  
Alexander Dreves ◽  
Frank Sirocko ◽  
Pieter M Grootes ◽  
Marie-Josée Nadeau
Keyword(s):  
Grain Size ◽  
Acid Treatment ◽  
Size Fraction ◽  
Sediment Layer ◽  
Bulk Sediment ◽  
Volcanic Origin ◽  
Size Fractions ◽  
Lake Sediment Core ◽  
Gravel Size ◽  
Grain Size Fractions

Radiocarbon measurements on bulk subaqueous sediments typically provide ages significantly older than actual time of deposition. This is generally caused by the presence of reworked organic compounds, which are depleted in 14C. To explore this issue of age heterogeneity, we collected 4 organic-rich samples from varying depths in a lake sediment core at the Gemündener Maar (Eifel, Germany), a lake of volcanic origin. We divided each sample into 5 standard grain-size fractions: gravel, sand, silt, clay, and 1 fraction smaller than 0.45 μm. These were cleaned separately using a standard acid-alkali-acid treatment. The highly organic gravel-size fraction provided the youngest 14C ages of all grain-size fractions and seems to be associated most closely with the time of deposition. By contrast, the silt and clay fractions show significantly older ages. If the investigated limnic sediment layer does not contain any identifiable terrestrial macrofossils, extracting and measuring coarser grain-size fractions instead of measuring bulk sediment samples will provide a better approximation of the time of sedimentation.

scholarly journals Submarine lava deltas of the 2018 eruption of Kīlauea volcano

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
S. Adam Soule ◽  
Michael Zoeller ◽  
Carolyn Parcheta
Keyword(s):  
Grain Size ◽  
Pore Pressure ◽  
Mechanistic Model ◽  
Large Fraction ◽  
Volcanic Hazards ◽  
Lava Flows ◽  
Coarse Grained ◽  
Fine Grained ◽  
Fine Grain ◽  
Delta Formation

AbstractHawaiian and other ocean island lava flows that reach the coastline can deposit significant volumes of lava in submarine deltas. The catastrophic collapse of these deltas represents one of the most significant, but least predictable, volcanic hazards at ocean islands. The volume of lava deposited below sea level in delta-forming eruptions and the mechanisms of delta construction and destruction are rarely documented. Here, we report on bathymetric surveys and ROV observations following the Kīlauea 2018 eruption that, along with a comparison to the deltas formed at Pu‘u ‘Ō‘ō over the past decade, provide new insight into delta formation. Bathymetric differencing reveals that the 2018 deltas contain more than half of the total volume of lava erupted. In addition, we find that the 2018 deltas are comprised largely of coarse-grained volcanic breccias and intact lava flows, which contrast with those at Pu‘u ‘Ō‘ō that contain a large fraction of fine-grained hyaloclastite. We attribute this difference to less efficient fragmentation of the 2018 ‘a‘ā flows leading to fragmentation by collapse rather than hydrovolcanic explosion. We suggest a mechanistic model where the characteristic grain size influences the form and stability of the delta with fine grain size deltas (Pu‘u ‘Ō‘ō) experiencing larger landslides with greater run-out supported by increased pore pressure and with coarse grain size deltas (Kīlauea 2018) experiencing smaller landslides that quickly stop as the pore pressure rapidly dissipates. This difference, if validated for other lava deltas, would provide a means to assess potential delta stability in future eruptions.

scholarly journals Mudrock Microstructure: A Technique for Distinguishing between Deep-Water Fine-Grained Sediments

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 653
Author(s):  
Shereef Bankole ◽  
Dorrik Stow ◽  
Zeinab Smillie ◽  
Jim Buckman ◽  
Helen Lever
Keyword(s):  
Grain Size ◽  
Deep Water ◽  
Sedimentary Facies ◽  
X Ray Diffraction ◽  
Weak Current ◽  
Large Area ◽  
Fine Grained ◽  
Mean Size ◽  
The Mean ◽  
Water Facies

Distinguishing among deep-water sedimentary facies has been a difficult task. This is possibly due to the process continuum in deep water, in which sediments occur in complex associations. The lack of definite sedimentological features among the different facies between hemipelagites and contourites presented a great challenge. In this study, we present detailed mudrock characteristics of the three main deep-water facies based on sedimentological characteristics, laser diffraction granulometry, high-resolution, large area scanning electron microscopy (SEM), and the synchrotron X-ray diffraction technique. Our results show that the deep-water microstructure is mainly process controlled, and that the controlling factor on their grain size is much more complex than previously envisaged. Retarding current velocity, as well as the lower carrying capacity of the current, has an impact on the mean size and sorting for the contourite and turbidite facies, whereas hemipelagite grain size is impacted by the natural heterogeneity of the system caused by bioturbation. Based on the microfabric analysis, there is a disparate pattern observed among the sedimentary facies; turbidites are generally bedding parallel due to strong currents resulting in shear flow, contourites are random to semi-random as they are impacted by a weak current, while hemipelagites are random to oblique since they are impacted by bioturbation.

scholarly journals Strain-Rate and Grain‒Size Effects in Ice

1987 ◽  
Vol 33 (115) ◽  
pp. 274-280 ◽  
Author(s):  
David M. Cole
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Transition Point ◽  
Boundary Migration ◽  
Peak Stress ◽  
Strain Rates ◽  
Thin Sections ◽  
Fine Grained ◽  
Lower Strain ◽  
Polycrystalline Ice

AbstractThis paper presents and discusses the results of constant deformation-rate tests on laboratory-prepared polycrystalline ice. Strain-rates ranged from 10−7to 10−1s−1, grain–size ranged from 1.5 to 5.8 mm, and the test temperature was −5°C.At strain-rates between 10−7and 10−3s−1, the stress-strain-rate relationship followed a power law with an exponent ofn= 4.3 calculated without regard to grain-size. However, a reversal in the grain-size effect was observed: below a transition point near 4 × 10−6s−1the peak stress increased with increasing grain-size, while above the transition point the peak stress decreased with increasing grain-size. This latter trend persisted to the highest strain-rates observed. At strain-rates above 10−3s−1the peak stress became independent of strain-rate.The unusual trends exhibited at the lower strain-rates are attributed to the influence of the grain-size on the balance of the operative deformation mechanisms. Dynamic recrystallization appears to intervene in the case of the finer-grained material and serves to lower the peak stress. At comparable strain-rates, however, the large-grained material still experiences internal micro-fracturing, and thin sections reveal extensive deformation in the grain-boundary regions that is quite unlike the appearance of the strain-induced boundary migration characteristic of the fine-grained material.

scholarly journals New Brightener for Zn-Fe Alloy Plating from Sulphate Bath

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
B. M. Praveen ◽  
T. V. Venkatesha
Keyword(s):  
Grain Size ◽  
Metal Ion ◽  
Condensation Product ◽  
Spectroscopic Studies ◽  
Sem Images ◽  
Alloy Electrodeposition ◽  
Fine Grained ◽  
Polarization Studies ◽  
Uv Visible ◽  
Sulphate Bath

Zn-Fe alloy electrodeposition was carried out in the presence of condensation product 2-{[(1E)-(3,4-dimethoxyphenyl)methylidene]amino}-3-hydroxypropanoic acid formed between veratraldehyde and serine in acid sulphate bath. Hull cell was used for optimizing the operating parameters and bath constituents. During deposition, the potential was shifted towards cathodic direction in the presence of addition agents and brightener. The polarization studies show that deposition taking place in basic bath and optimum bath was 1.08 and 1.15 V, respectively. Current efficiency and throwing power were reached around 85% and 26%, respectively. The SEM images of bright deposit indicated its fine-grained nature and appreciable reduction in the grain size. XRD studies have showed that the grain size of the deposit generated from optimum bath was 16 nm. UV-visible spectroscopic studies confirm the formation of complex between metal ion and brightener.

Measuring Bed Load Transport Rates by Grain-Size Fraction Using the Swiss Plate Geophone Signal at the Erlenbach

2016 ◽  
Vol 142 (5) ◽  
pp. 04016003 ◽  
Author(s):  
Carlos R. Wyss ◽  
Dieter Rickenmann ◽  
Bruno Fritschi ◽  
Jens M. Turowski ◽  
Volker Weitbrecht ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Fraction ◽  
Bed Load ◽  
Load Transport ◽  
Bed Load Transport

scholarly journals Influence of Steel Grain Size on Residual Stress in Grinding Processing

2010 ◽  
Vol 638-642 ◽  
pp. 2389-2394 ◽  
Author(s):  
Masahide Gotoh ◽  
Katsuhiro Seki ◽  
M. Shozu ◽  
Hajime Hirose ◽  
Toshihiko Sasaki
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Grain Size ◽  
Stress State ◽  
Mechanical Grinding ◽  
Fine Grained ◽  
Residual Stress State ◽  
Analysis Methods ◽  
Average Grain Size ◽  
Fine Grained Steels

The fine-grained rolling steels NFG600 and the conventional usual rolling steels SM490 were processed by sand paper polishing and mechanical grinding to compare the residual stress generated after processing. The average grain size of NFG600 and SM490 is 3 μm and 15μm respectively. Therefore improvement of mechanical properties for such fine-grained steels is expected, it is important to understand the residual stress state of new fine-grained materials with processing. In this study, multi axial stresses of two kinds of specimens after polishing and grinding were measured by three kinds of analysis methods including cos-ψ method. As a result, as for σ33, the stress of NFG was compression, though that of SM490 was tension.

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