In situ determination of porewater gases by underwater flow‐through membrane inlet mass spectrometry

Bell, Ryan J.; Savidge, William B.; Toler, Strawn K.; Byrne, Robert H.; Short, R.T.

doi:10.4319/lom.2012.10.117

Cited by 9 publications

(12 citation statements)

References 42 publications

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“…These ripples formed during a neap tidal period in which benthic stresses were barely above the critical threshold. The sediment oxygen chemocline moved vertically by *2 cm within the sediment in response to the ripples, suggesting that changes in porewater fluxes accompanied the changes in bedform geometry (Bell et al 2012). Given the absence of ripples identified in the ABS data, it is possible that their presence adjacent to the instrument frame represents a wake effect of the bottom currents deflecting around the large object on the seafloor.…”

Section: Forcingmentioning

confidence: 97%

“…Continuous measurement of bed height using a downward-looking acoustic backscatter sensor (ABS) on a nearby tripod revealed no instances of small migratory ripples on the seafloor during the two deployments (G. Voulgaris, unpublished data). Small mobile ripples were observed around benthic instrumentation at the site during late August 2008 (Bell et al 2012). These ripples formed during a neap tidal period in which benthic stresses were barely above the critical threshold.…”

Section: Forcingmentioning

confidence: 99%

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Using a Thermal Proxy to Examine Sediment–Water Exchange in Mid-Continental Shelf Sandy Sediments

2016

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Fluid exchange across the sediment-water interface in a sandy open continental shelf setting was studied using heat as a tracer. Summertime tidal oscillation of cross-shelf thermal fronts on the South Atlantic Bight provided a sufficient signal at the sedimentwater interface to trace the advective and conductive transport of heat into and out of the seabed, indicating rapid flushing of ocean water through the upper 10-40 cm of the sandy seafloor. A newly developed transport model was applied to the in situ temperature data set to estimate the extent to which heat was transported by advection rather than conduction. Heat transported by shallow 3-D porewater flow processes was accounted for in the model by using a dispersion term, the depth and intensity of which reflected the depth and intensity of shallow flushing. Similar to the results of past studies in shallower and more energetic nearshore settings, transport of heat was greater when higher near-bed velocities and shear stresses occurred over a rippled bed. However, boundary layer processes by themselves were insufficient to promote non-conductive heat transport. Advective heat transport only occurred when both larger boundary layer stresses and thermal instabilities within the porespace were present. The latter process is dependent on shelf-scale heating and cooling of bottom water associated with upwelling events that are not coupled to localscale boundary layer processes.

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Section: Forcingmentioning

confidence: 97%

Section: Forcingmentioning

confidence: 99%

Using a Thermal Proxy to Examine Sediment–Water Exchange in Mid-Continental Shelf Sandy Sediments

2016

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“…McMurtry et al (2005) experimented with a fuel cell power source, but this technique still employs a finite power source. In a field deployment, Bell et al (2012) successfully extended the endurance of their battery-powered UMS system from a 12-h battery charge to a 54-h continuous operational deployment by incorporating a renewable battery system, which required a manual exchange of batteries with the buoy-cabled UMS system twice daily. There are many trade-offs between instrument performance and power consumption.…”

Section: Power Requirementsmentioning

confidence: 99%

“…Consequently, there is an acute need for in situ sensors that can measure a variety of key chemical species [e.g., oxygen, nutrients, biogenic gases, and dissolved inorganic carbon (DIC)] on spatial and temporal scales that match the scales of the processes being investigated. Ideally, these sensors should have a large dynamic concentration range, excellent detection limits, quick response time, high stability, and resistance to fouling (Moore et al, 2009;Bell et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…For example, these systems have been placed on mobile platforms to produce two-and three-dimensional underwater maps of chemical distributions (e.g., Wenner et al, 2004;Camilli et al, 2010;Gentz and Schlüter, 2012). Other UMS systems have been developed to target understudied areas of ocean chemistry, such as in situ isotope ratios (Camilli and Duryea, 2009) and porewater composition (Bell et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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A Review of the Emerging Field of Underwater Mass Spectrometry

et al. 2016

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Mass spectrometers are versatile sensor systems, owing to their high sensitivity and ability to simultaneously measure multiple chemical species. Over the last two decades, traditional laboratory-based membrane inlet mass spectrometers have been adapted for underwater use. Underwater mass spectrometry (UMS) has drastically improved our capability to monitor a broad suite of gaseous compounds (e.g., dissolved atmospheric gases, light hydrocarbons, and volatile organic compounds) in the aquatic environment. Here we provide an overview of the progress made in the field of UMS since its inception in the 1990s to the present. In particular, we discuss the approaches undertaken by various research groups in developing in situ mass spectrometers. We also provide examples to illustrate how underwater mass spectrometers have been used in the field. Finally, we present future trends in the field of in situ mass spectrometry. Most of these efforts are aimed at improving the quality and spatial and temporal scales of chemical measurements in the ocean. By providing up-to-date information on UMS, this review offers guidance for researchers interested in adapting this technology as well as goals for future progress in the field.

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A case for addressing the unresolved role of permeable shelf sediments in ocean denitrification

Chua

Huettel

Fennel

et al. 2021

Limnol Oceanogr Letters

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Human activities release vast amounts of reactive nitrogen, profoundly influencing the functioning of marine ecosystems. On the inner shelf, where these effects are most pronounced, sediments have emerged as potential hotspots of reactive nitrogen removal-and they are therefore increasingly thought to play a key role in the ocean nitrogen cycle. Despite their potential importance, shelf sediments are still overlooked in global models of ocean nitrogen and carbon cycles, limiting model accuracy and predictive power. Through analysis of recent work, we identified unresolved questions and controversies, and propose a three-pronged approach to improve our mechanistic understanding and modeling of nitrogen removal on the continental shelf and in the global ocean.

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In situ determination of porewater gases by underwater flow‐through membrane inlet mass spectrometry

Cited by 9 publications

References 42 publications

Using a Thermal Proxy to Examine Sediment–Water Exchange in Mid-Continental Shelf Sandy Sediments

Using a Thermal Proxy to Examine Sediment–Water Exchange in Mid-Continental Shelf Sandy Sediments

A Review of the Emerging Field of Underwater Mass Spectrometry

A case for addressing the unresolved role of permeable shelf sediments in ocean denitrification

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