An investigation of early diagenetic process in marine coastal environments by the diffusive gradient in thin films (DGT) technique
An investigation of early diagenetic process in marine coastal environments by the diffusive gradient in thin films (DGT) technique
Model homogeneous sediment systems, in which biological and physical mixing processes were excluded, have been used for the application of the Diffusive Gradient in Thin films (DGT) technique to the study of early diagenetic processes in coastal/estuarine sediments. Two different temperature and oxygen regimes (simulated summer and simulated winter conditions) were used. Using oxygen, pore water and solid phase metal data, and nutrient measurements in combination it has been possible to identify the sediment redox zones. The sequential microbial reduction of O2, NO3- + NO2-, Mn and Fe led to changing of the redoxcline position during the incubation experiments. Large chemical gradients in the dissolved Fe(II), Mn(II) and NO3- + NO2-, in the top layers of sediment, indicate their use as electron acceptors associated with metabolic processes. These gradients were more pronounced during the simulated summer conditions (SedIncII) than the simulated winter conditions (SedIncII) due to different microbial activity and induced redox changes.
The DGT profiles reflected the metal mobilisation and distribution in the sediment, which ultimately depended on varying microbial activity during the incubation period. In particular, the profiles reflected the segregation of diagenetic reactions into different redox zones in the sediment. As the terminal Electron Acceptor Process (TEAPs) zones moved upwards in the sediment column the metal precipitation/dissolution intervals changed depth over the incubation period. Consequently, the DGT profiles recorded integrated measurements of Fe(II), Mn(II), and Zn(II) fluxes, reflecting the transient depth intervals of metal reductive dissolution in the sediment column over the deployment period.
The DGT high resolution measurements accounted for the Fe/Mn redox cycle in the top layers of the sediment. The detail of this process was not evident using the much coarser resolution provided by the centrifugation measurements, and was only clearly demonstrated using the DGT technique. In SedIncI, Fe and Mn redox cycle interacted with each other across the redoxcline, through mechanisms of precipitation and dissolution.
University of Southampton
Soares, Jose Antonio
0a19aee2-26c0-413a-8036-298eee8ef5f9
1998
Soares, Jose Antonio
0a19aee2-26c0-413a-8036-298eee8ef5f9
Soares, Jose Antonio
(1998)
An investigation of early diagenetic process in marine coastal environments by the diffusive gradient in thin films (DGT) technique.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Model homogeneous sediment systems, in which biological and physical mixing processes were excluded, have been used for the application of the Diffusive Gradient in Thin films (DGT) technique to the study of early diagenetic processes in coastal/estuarine sediments. Two different temperature and oxygen regimes (simulated summer and simulated winter conditions) were used. Using oxygen, pore water and solid phase metal data, and nutrient measurements in combination it has been possible to identify the sediment redox zones. The sequential microbial reduction of O2, NO3- + NO2-, Mn and Fe led to changing of the redoxcline position during the incubation experiments. Large chemical gradients in the dissolved Fe(II), Mn(II) and NO3- + NO2-, in the top layers of sediment, indicate their use as electron acceptors associated with metabolic processes. These gradients were more pronounced during the simulated summer conditions (SedIncII) than the simulated winter conditions (SedIncII) due to different microbial activity and induced redox changes.
The DGT profiles reflected the metal mobilisation and distribution in the sediment, which ultimately depended on varying microbial activity during the incubation period. In particular, the profiles reflected the segregation of diagenetic reactions into different redox zones in the sediment. As the terminal Electron Acceptor Process (TEAPs) zones moved upwards in the sediment column the metal precipitation/dissolution intervals changed depth over the incubation period. Consequently, the DGT profiles recorded integrated measurements of Fe(II), Mn(II), and Zn(II) fluxes, reflecting the transient depth intervals of metal reductive dissolution in the sediment column over the deployment period.
The DGT high resolution measurements accounted for the Fe/Mn redox cycle in the top layers of the sediment. The detail of this process was not evident using the much coarser resolution provided by the centrifugation measurements, and was only clearly demonstrated using the DGT technique. In SedIncI, Fe and Mn redox cycle interacted with each other across the redoxcline, through mechanisms of precipitation and dissolution.
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Published date: 1998
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Local EPrints ID: 463329
URI: http://eprints.soton.ac.uk/id/eprint/463329
PURE UUID: 1875e34b-79c2-42df-ad6d-62a1644ffb42
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Date deposited: 04 Jul 2022 20:50
Last modified: 23 Jul 2022 01:09
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Author:
Jose Antonio Soares
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