Exploring the Quaternary mercury cycle
Exploring how climate-driven processes impact biogeochemical cycles is critical for understanding how discrete components of the Earth system have interacted through time. Mercury (Hg) is a toxic metal released into the atmosphere as a result of natural processes and more recently by human activiti...
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| Format: | Thesis |
| Language: | English |
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2024
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| _version_ | 1817930680255905792 |
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| author | Paine, AR |
| author2 | Robinson, S |
| author_facet | Robinson, S Paine, AR |
| author_sort | Paine, AR |
| collection | OXFORD |
| description | Exploring how climate-driven processes impact biogeochemical cycles is critical for understanding how discrete components of the Earth system have interacted through time. Mercury (Hg) is a toxic metal released into the atmosphere as a result of natural processes and more recently by human activities, yet whose long-term (>10-kyr) processing remains in many ways poorly understood in the terrestrial realm. More specifically, there is a need for closer examination of which mechanisms govern the transport, accumulation, and cycling of Hg in this domain across broad temporal and spatial scales, and how long-term changes in the terrestrial Hg cycle may translate to the sedimentary record. This thesis presents three new Hg datasets from Lake Ohrid (Southeast Europe; 1360–0 ka), Lake Prespa (Southeast Europe; 92–0 ka), and Lake Bosumtwi (West Africa; 96–0 ka). Each are assessed relative to high-resolution geophysical, sedimentological and micropaleontological measurements taken from their corresponding cores, in order to better understand which mechanisms are most significant for transport, accumulation, and cycling of Hg in these environments over multiple millennia. These successions offer new and valuable perspectives on the terrestrial Hg cycle, and demonstrate that climate-driven changes in the Hg cycle can be effectively recorded by lacustrine sediments over many hundreds, even thousands of years. However, they are also separated by the extent to which different sedimentary fractions can (or cannot) explain time-varying patterns in Hg, and the extent to which different environmental processes can (or cannot) explain links between Hg cycle perturbations and millennial-scale climate changes. These observations suggest that identical stratigraphic signals are unlikely to be recorded in separate lakes subject to the same climate perturbations, processes, or phenomena, and that local-scale differences in depositional setting, lake bathymetry, Hg sources, hydrology, and/or catchment structure may cause shifts in terrestrial Hg cycling that do not always scale, at least linearly, with the severity and/or expression of the underlying climate perturbations. It is evident that a comprehensive understanding of a lake system and its history is critical in order to accurately distinguish the Hg signals that are climate-mediated, from those that may emerge as a function of local, independent processes. Nonetheless, this work highlights how there is great scope for continued development of millennial-scale Hg archives spanning a diverse range of spatiotemporal settings: archives that will permit better characterization of the processes impacting Hg cycling in lacustrine sediments on long timescales, and provide a solid foundation for exploring how this cycle has evolved throughout the Quaternary. |
| first_indexed | 2024-12-09T03:09:58Z |
| format | Thesis |
| id | oxford-uuid:9941f28f-da50-491b-afd2-e15265cbb092 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-12-09T03:09:58Z |
| publishDate | 2024 |
| record_format | dspace |
| spelling | oxford-uuid:9941f28f-da50-491b-afd2-e15265cbb0922024-10-08T09:32:46ZExploring the Quaternary mercury cycle Thesishttp://purl.org/coar/resource_type/c_db06uuid:9941f28f-da50-491b-afd2-e15265cbb092EnglishHyrax Deposit2024Paine, ARRobinson, SMather, TPyle, DSmith Johnson, VJones, MExploring how climate-driven processes impact biogeochemical cycles is critical for understanding how discrete components of the Earth system have interacted through time. Mercury (Hg) is a toxic metal released into the atmosphere as a result of natural processes and more recently by human activities, yet whose long-term (>10-kyr) processing remains in many ways poorly understood in the terrestrial realm. More specifically, there is a need for closer examination of which mechanisms govern the transport, accumulation, and cycling of Hg in this domain across broad temporal and spatial scales, and how long-term changes in the terrestrial Hg cycle may translate to the sedimentary record. This thesis presents three new Hg datasets from Lake Ohrid (Southeast Europe; 1360–0 ka), Lake Prespa (Southeast Europe; 92–0 ka), and Lake Bosumtwi (West Africa; 96–0 ka). Each are assessed relative to high-resolution geophysical, sedimentological and micropaleontological measurements taken from their corresponding cores, in order to better understand which mechanisms are most significant for transport, accumulation, and cycling of Hg in these environments over multiple millennia. These successions offer new and valuable perspectives on the terrestrial Hg cycle, and demonstrate that climate-driven changes in the Hg cycle can be effectively recorded by lacustrine sediments over many hundreds, even thousands of years. However, they are also separated by the extent to which different sedimentary fractions can (or cannot) explain time-varying patterns in Hg, and the extent to which different environmental processes can (or cannot) explain links between Hg cycle perturbations and millennial-scale climate changes. These observations suggest that identical stratigraphic signals are unlikely to be recorded in separate lakes subject to the same climate perturbations, processes, or phenomena, and that local-scale differences in depositional setting, lake bathymetry, Hg sources, hydrology, and/or catchment structure may cause shifts in terrestrial Hg cycling that do not always scale, at least linearly, with the severity and/or expression of the underlying climate perturbations. It is evident that a comprehensive understanding of a lake system and its history is critical in order to accurately distinguish the Hg signals that are climate-mediated, from those that may emerge as a function of local, independent processes. Nonetheless, this work highlights how there is great scope for continued development of millennial-scale Hg archives spanning a diverse range of spatiotemporal settings: archives that will permit better characterization of the processes impacting Hg cycling in lacustrine sediments on long timescales, and provide a solid foundation for exploring how this cycle has evolved throughout the Quaternary. |
| spellingShingle | Paine, AR Exploring the Quaternary mercury cycle |
| title | Exploring the Quaternary mercury cycle
|
| title_full | Exploring the Quaternary mercury cycle
|
| title_fullStr | Exploring the Quaternary mercury cycle
|
| title_full_unstemmed | Exploring the Quaternary mercury cycle
|
| title_short | Exploring the Quaternary mercury cycle
|
| title_sort | exploring the quaternary mercury cycle |
| work_keys_str_mv | AT painear exploringthequaternarymercurycycle |