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Experimental Characterization of Marine Aggregate Fragmentation Strength Through Laboratory and Field Methods.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Experimental Characterization of Marine Aggregate Fragmentation Strength Through Laboratory and Field Methods./
Author:	Song, Yixuan.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2023,
Description:	235 p.
Notes:	Source: Dissertations Abstracts International, Volume: 85-03, Section: B.
Contained By:	Dissertations Abstracts International85-03B.
Subject:	Plankton. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30551170
ISBN:	9798380257183

Experimental Characterization of Marine Aggregate Fragmentation Strength Through Laboratory and Field Methods.
Song, Yixuan.

Experimental Characterization of Marine Aggregate Fragmentation Strength Through Laboratory and Field Methods. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 235 p.

Source: Dissertations Abstracts International, Volume: 85-03, Section: B.

Thesis (Ph.D.)--The Pennsylvania State University, 2023.

Organic particulate matter plays a crucial role in the carbon transport through the oceanic water column. The size of the particulate matter, influenced by hydrodynamic fragmentation, primarily regulates the sinking flux of carbon from the surface ocean. Disaggregation, caused by turbulence-induced shear, acts to fracture or erode large particles into slower-settling sub-aggregates and primary particles. The strength and breakup response of organic marine aggregates (i.e., marine snow particles consisting of phytoplankton) is poorly understood, limiting our ability to accurately predict marine particle transport effects on the global carbon cycle. In this dissertation, we have implemented field fragmentation measurements of naturally occurring marine aggregates and incorporated laboratory experiments in parallel to explain the formation and disruption mechanisms of marine snow aggregates.We have developed one in-situ disaggregation system and measured the fragmentation of aggregates during two recent field deployments in the Northeastern United States Continental Shelf and Lake Tahoe. The prototype used one variable speed thruster to draw the fluid flow through a long tube and generated fully developed turbulent flows inside. By adjusting the thruster speed, we obtained varying flow conditions from a laminar flow to a strong turbulent flow. The disaggregation system exposed naturally occurring particles to this calibrated flow condition inside the tube. We also employed a programmable controller with power sources that allows for in-situ measurements at a depth of up to 200 m. We used a submersible digital holographic camera to capture particle size statistics and images in the Northeastern United States Continental Shelf, and deployed an underwater particle size meter during the deployment in Lake Tahoe. Fragmentation results have validated the in-situ disaggregation system and showed particle fragmentation due to turbulence in the ocean and lake environments.In the laboratory, we cultured two diatom species, Odontella aurita and Skeletonema grethae, to prepare simulated marine aggregates. We have developed a novel rotating/oscillating tank that can form aggregates and perform breakup experiments in a controlled environment. This novel tank does not need any manipulation of aggregates at all. The facility can additionally provide shear rates across a wide range of the ocean from very low turbulence in the mixed layer to high shear in the surface ocean. We formed diatom aggregates by operating the tank at a constant rotation speed and disrupted them when the tank underwent a harmonic oscillation around its central axis, which was oriented horizontally.The flow motion inside the rotating/oscillating tank was a superposition of a solid body rotation and a harmonic oscillatory flow that was also an extension of the famous Stokes' second problem inside a cylindrical geometric configuration. We provided an analytical solution to this viscous oscillatory flow using the Laplace Transform and Residue Theorem. We detailed the transient starting condition and the quasi steady fluid motion, which we presented along with a particle image velocimetry experiment for validation. Given proper boundary conditions, this roller tank created calibrated laminar shear that is similar in magnitude to that in the ocean.With high-speed imaging techniques, we captured the fragmentation of laboratory-made diatom aggregates exposed to the calibrated oscillatory flow. We have also developed a unique image processing method that enabled continuous tracking of particle positions, sizes, and morphologies, as well as the determination of individual aggregate breakup events. The image processing consisted of background removal, particle identification, particle matching, and breakup detection. The analytical solution of fluid flow allowed us to couple the hydrodynamic conditions to the recorded time history. This method has great potential to capture breakup events of large marine snow particles, quantify the aggregate morphological changes leading up to and at breakup, and provide data sufficient for statistical analysis of laboratory aggregate populations. We tested the method using laboratory-cultured Odontella aurita. These fragmented aggregates underwent substantial morphological evolutions prior to the fragmentation.The formation theory of colloidal particles is relatively well established but the knowledge of biological bonding governing the strength of naturally occurring aggregates is still limited. To better comprehend fragmentation processes and adhesion forces, we implemented aggregate breakup experiments with diatom aggregates and colloidal flocs made in the laboratory from polystyrene and polyethylene microspheres. We captured the fragmentation of diatom aggregates and polystyrene flocs after substantial deformation, while polyethylene aggregates did not break. The fragmentation results provided upper and lower limits of the biological bonding strength of diatom aggregates using two colloidal floc types. Additionally, we employed a force balance model to evaluate attractive interactions within clusters of particles using time series of shear and morphology. We found that the fractal structures of the aggregates lead to a power law of breakup strength with size. This study also reveals time-integrated stress is influential in floc fragmentation.Finally, we summarize our contributions related to the fragmentation of marine snow and its influence on carbon transport. Knowing the breakup strength of marine snow can improve our predictions of particle fragmentation in the particle population balance, which further enhances our understanding of the oceanic carbon sequestration and the mass transport in the biological carbon pump. We additionally identify multiple priorities for the continuation of this work and address recommended future directions.

ISBN: 9798380257183Subjects--Topical Terms:

1299572
Plankton.
Subjects--Index Terms:

Marine aggregates

Experimental Characterization of Marine Aggregate Fragmentation Strength Through Laboratory and Field Methods.
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500 $a Advisor: Rau, Matthew J.
502 $a Thesis (Ph.D.)--The Pennsylvania State University, 2023.
520 $a Organic particulate matter plays a crucial role in the carbon transport through the oceanic water column. The size of the particulate matter, influenced by hydrodynamic fragmentation, primarily regulates the sinking flux of carbon from the surface ocean. Disaggregation, caused by turbulence-induced shear, acts to fracture or erode large particles into slower-settling sub-aggregates and primary particles. The strength and breakup response of organic marine aggregates (i.e., marine snow particles consisting of phytoplankton) is poorly understood, limiting our ability to accurately predict marine particle transport effects on the global carbon cycle. In this dissertation, we have implemented field fragmentation measurements of naturally occurring marine aggregates and incorporated laboratory experiments in parallel to explain the formation and disruption mechanisms of marine snow aggregates.We have developed one in-situ disaggregation system and measured the fragmentation of aggregates during two recent field deployments in the Northeastern United States Continental Shelf and Lake Tahoe. The prototype used one variable speed thruster to draw the fluid flow through a long tube and generated fully developed turbulent flows inside. By adjusting the thruster speed, we obtained varying flow conditions from a laminar flow to a strong turbulent flow. The disaggregation system exposed naturally occurring particles to this calibrated flow condition inside the tube. We also employed a programmable controller with power sources that allows for in-situ measurements at a depth of up to 200 m. We used a submersible digital holographic camera to capture particle size statistics and images in the Northeastern United States Continental Shelf, and deployed an underwater particle size meter during the deployment in Lake Tahoe. Fragmentation results have validated the in-situ disaggregation system and showed particle fragmentation due to turbulence in the ocean and lake environments.In the laboratory, we cultured two diatom species, Odontella aurita and Skeletonema grethae, to prepare simulated marine aggregates. We have developed a novel rotating/oscillating tank that can form aggregates and perform breakup experiments in a controlled environment. This novel tank does not need any manipulation of aggregates at all. The facility can additionally provide shear rates across a wide range of the ocean from very low turbulence in the mixed layer to high shear in the surface ocean. We formed diatom aggregates by operating the tank at a constant rotation speed and disrupted them when the tank underwent a harmonic oscillation around its central axis, which was oriented horizontally.The flow motion inside the rotating/oscillating tank was a superposition of a solid body rotation and a harmonic oscillatory flow that was also an extension of the famous Stokes' second problem inside a cylindrical geometric configuration. We provided an analytical solution to this viscous oscillatory flow using the Laplace Transform and Residue Theorem. We detailed the transient starting condition and the quasi steady fluid motion, which we presented along with a particle image velocimetry experiment for validation. Given proper boundary conditions, this roller tank created calibrated laminar shear that is similar in magnitude to that in the ocean.With high-speed imaging techniques, we captured the fragmentation of laboratory-made diatom aggregates exposed to the calibrated oscillatory flow. We have also developed a unique image processing method that enabled continuous tracking of particle positions, sizes, and morphologies, as well as the determination of individual aggregate breakup events. The image processing consisted of background removal, particle identification, particle matching, and breakup detection. The analytical solution of fluid flow allowed us to couple the hydrodynamic conditions to the recorded time history. This method has great potential to capture breakup events of large marine snow particles, quantify the aggregate morphological changes leading up to and at breakup, and provide data sufficient for statistical analysis of laboratory aggregate populations. We tested the method using laboratory-cultured Odontella aurita. These fragmented aggregates underwent substantial morphological evolutions prior to the fragmentation.The formation theory of colloidal particles is relatively well established but the knowledge of biological bonding governing the strength of naturally occurring aggregates is still limited. To better comprehend fragmentation processes and adhesion forces, we implemented aggregate breakup experiments with diatom aggregates and colloidal flocs made in the laboratory from polystyrene and polyethylene microspheres. We captured the fragmentation of diatom aggregates and polystyrene flocs after substantial deformation, while polyethylene aggregates did not break. The fragmentation results provided upper and lower limits of the biological bonding strength of diatom aggregates using two colloidal floc types. Additionally, we employed a force balance model to evaluate attractive interactions within clusters of particles using time series of shear and morphology. We found that the fractal structures of the aggregates lead to a power law of breakup strength with size. This study also reveals time-integrated stress is influential in floc fragmentation.Finally, we summarize our contributions related to the fragmentation of marine snow and its influence on carbon transport. Knowing the breakup strength of marine snow can improve our predictions of particle fragmentation in the particle population balance, which further enhances our understanding of the oceanic carbon sequestration and the mass transport in the biological carbon pump. We additionally identify multiple priorities for the continuation of this work and address recommended future directions.
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