Seafloor Processes and Geotechnology

Chaney, Ronald C.; Almagor, Gideon

doi:10.1201/b19211

Cited by 5 publications

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For instance, the corer inner diameter can be increased up to 100 mm, as a maximum possible core diameter, because it can be still frozen with a mixture of dry ice and ethanol within reasonable time (<80 min; Renberg and Hansson ). A larger diameter improves coring quality considerably by minimizing the adverse effects of wall friction, down‐bowing of sediments along the tube walls and core shortening (Baxter et al ; Pedersen ; Blomqvist ; Chaney and Almagor ). The amplitude of structural disturbances can therefore be reduced in comparison to commonly used lance freeze corer, for which Liernur et al () found a high variability of the vertical displacement of the sediment layer with an average of 3.7 ± 1.2 cm.…”

Section: Conclusion and Recommendationsmentioning

confidence: 99%

A novel freeze corer for characterization of methane bubbles and assessment of coring disturbances

Dück

Liu

Lorke

et al. 2019

Limnology & Ocean Methods

View full text Add to dashboard Cite

Aquatic ecosystems with organic‐rich sediments are a globally significant source of methane to the atmosphere. In shallow waters, ebullition is often a dominant emission pathway of methane. Current knowledge on the processes controlling gas bubble formation and persistence in aquatic sediments is limited. An important prerequisite for accurate quantification of the structure and methane bubbles in sediment samples is to preserve the ambient in situ conditions during the withdrawal process and further analysis. A novel freeze corer has been developed that facilitates sampling of gas‐bearing soft sediments for X‐ray computer tomography. The sampler allows freezing sediment inside a double‐walled corer with a mixture of dry ice and ethanol. This corer has moderate costs and offers important advantages for gassy sediment sampling. Its simplicity and robustness allow to perform sampling from a small boat and the ability to characterize in situ sediment features. The applicability of this freeze coring technique for gas bubble quantification was validated during laboratory experiments aimed to investigate the effects of freezing on sediment gas content, bubble size distribution, and their geometry by comparing computer tomography scans of unfrozen vs. frozen cores. The performance of the corer was further evaluated during field conditions in Lake Kinneret (the Sea of Galilee, Israel). The results demonstrate the suitability of the freeze‐coring method for in situ preservation of gas‐bearing sediments. The sediment structure, however, showed some displacements of sediments layers and bubble abundance in some core regions. Future investigations are needed to address the nature of disturbances of the frozen sediment.

show abstract

Section: Conclusion and Recommendationsmentioning

confidence: 99%

A novel freeze corer for characterization of methane bubbles and assessment of coring disturbances

Dück

Liu

Lorke

et al. 2019

Limnology & Ocean Methods

View full text Add to dashboard Cite

show abstract

“…The soft sediments are driven aside as the core barrel containing high‐density sediment penetrates deeper (Morton and White ). Clayey and silty sediments are compressed more than light, unconsolidated, organic sediments and a large core diameter minimizes shortening (Blomqvist ; Chaney and Almagor ).…”

Section: Coring Disturbancesmentioning

confidence: 99%

Laboratory and field investigations on freeze and gravity core sampling and assessment of coring disturbances with implications on gas bubble characterization

Dück

Lorke

Jokiel

et al. 2019

Limnology & Ocean Methods

View full text Add to dashboard Cite

The quantification of greenhouse gas emissions from aquatic ecosystems requires knowledge about the spatial and temporal dynamics of free gas in sediments. Freezing the sediment in situ offers a promising method for obtaining gas‐bearing sediment samples, unaffected by changes in hydrostatic pressure and sample temperature during core withdrawal and subsequent analysis. This article presents a novel freeze coring technique to preserve the in situ stratigraphy and gas bubble characteristics. Nondestructive X‐ray computed tomography (CT) scans were used to identify and characterize coring disturbances of gravity and freeze cores associated with gassy sediment, as well as the effect of the freezing process on the gas bubble characteristics. Real‐time X‐ray CT scans were conducted to visualize the progression of the freezing process. Additional experiments were conducted to determine the freezing rate to assess the probability of sediment particle/bubble migration, and gas bubble nucleation at the phase transition of pore water to ice. The performance of the freeze coring technique was evaluated under field conditions in Olsberg and Urft Reservoir (Germany). The results demonstrate the capability of the freeze coring technique for the preservation of gas‐bearing sediments and the analysis of gas bubble distribution pattern in both reservoirs. Nevertheless, the obtained cores showed that nearly all gravity and freeze cores show some degree of coring disturbances.

show abstract

“…Sediments are “sucked” evenly and undisturbed into the sampling tube, sample entry is facilitated and core shortening reduced or almost eliminated (Blomqvist ; Nesje ; Mudroch and MacKnight ; Glew et al ). Large core diameter ; small coring tubes, although easier to push, encounter excessive internal friction in the core, and recovery may be incomplete (Glew et al ). Large‐diameter coring tubes minimize wall friction, down‐bowing of sediments along the tube walls and core shortening, considerably improving core quality (Pedersen ; Blomqvist ; Chaney and Almagor ). Slow entry speed ; most gravity or piston corers gain their penetration energy from a free fall starting at a considerable distance above ground, which leads to a fast penetration. Our corer is provided with a supporting tripod that is gently lowered to the sea bottom; only after landing does the coring tube start sinking into the sediment from a pre‐set height of about 5–10 cm above the sediment surface and is then pushed further down by the hammering weights.…”

Section: Assessmentmentioning

confidence: 99%

“…This makes them less suitable for studies requiring greater amounts of material or longer, multiple cores of equal length in sediments of different caliber (Nesje ; Adachi et al ). Furthermore, gravity corers are prone to disturb the water‐rich uppermost sediment layers upon impact due to the shock wave they generate during descent (Burke ; McIntyre ; Parker and Sills ; Blomqvist ; Glew et al ; Chaney and Almagor ). They may also produce considerable entry deficits (penetration minus sample entry), which can “shorten” the retrieved sediment column by up to 50% (Wright ; Skinner and McCave ).…”

mentioning

confidence: 99%

An innovative piston corer for large‐volume sediment samples

Gallmetzer

Haselmair²,

Stachowitsch³

et al. 2016

Limnol. Oceanogr. Methods

View full text Add to dashboard Cite

Coring is one of several standard procedures to extract sediments and their faunas from open marine, estuarine, and limnic environments. Achieving sufficiently deep penetration, obtaining large sediment volumes in single deployments, and avoiding sediment loss upon retrieval remain problematic. We developed a piston corer with a diameter of 16 cm that enables penetration down to 1.5 m in a broad range of soft bottom types, yields sufficient material for multiple analyses, and prevents sediment loss due to a specially designed hydraulic core catcher. A novel extrusion system enables very precise slicing and preserves the original sediment stratification by keeping the liners upright. The corer has moderate purchase costs and a robust and simple design that allows for a deployment from relatively small vessels as available at most marine science institutions. It can easily be operated by two to three researchers rather than by specially trained technicians. In the northern Adriatic Sea, the corer successfully extracted more than 50 cores from a range of fine mud to coarse sand, at water depths from three to 45 m. The initial evaluation of the cores demonstrated their usefulness for fauna sequences along with heavy metal, nutrient and pollutant analyses. Their length is particularly suited for historical ecological work requiring sedimentary and faunal sequences to reconstruct benthic communities over the last millennia.

show abstract

Seafloor Processes and Geotechnology

Cited by 5 publications

References 0 publications

A novel freeze corer for characterization of methane bubbles and assessment of coring disturbances

A novel freeze corer for characterization of methane bubbles and assessment of coring disturbances

Laboratory and field investigations on freeze and gravity core sampling and assessment of coring disturbances with implications on gas bubble characterization

An innovative piston corer for large‐volume sediment samples

Contact Info

Product

Resources

About